Mark Chalmers

A few months ago, I spotted the earthly remains of an Artemide uplighter listed for sale on an online auction site. I enjoy tinkering and assembling things from bits – on a smaller scale but in the same way that folk with acres of land buy old bulldozers, saving them from the scrapheap and then restoring them to running order.

I already had the components of roughly one-and-a-half uplighters, including three glass shades which were different colours. In theory, this was an opportunity to put together two complete lamps, because the listing noted that the vendor had bought a new glass shade from Artemide but never got around to fitting it to the lamp. The new one matched one of the three I already owned, and parts of another uplighter were chucked in for good measure.

Ebay and other online auction sites such as Vinterior and Etsy are a good source of second-hand furniture and fittings – but the latter two are awash with dealers, plus amateurs with greedily optimistic expectations of what things are worth. Ebay has some of those, too, but there are also lots of folk simply trying to clear out their loft or garage. Their prices are much more realistic, but Caveat Emptor still applies.

After some haggling, I bought the lamps and arranged to collect them a few days later. The address was a large house in the leafy western suburbs of Edinburgh, and a cheerful chap in jumbo cords and cardigan met me at the door with a box of lamp components. He apologised that some were a wee bit rusty, after having lain abandoned in the garage for a few years.

It wasn’t difficult to read between the lines. The glass shade had broken and he’d decided to buy a replacement, without checking first how to fit it. Perhaps it came with instructions, but those had been lost along the way. Perhaps husband or wife were practical folk who are good with their hands – but on the evidence I saw, that seems unlikely.

Maybe they’re just clumsy, a throwback to our pre-historic Neanderthal ancestors who lacked the ability to use tools. We all know folk who trip over their feet and slice their fingertips while chopping onions. An alternative is that they’re giant-brained people who have evolved beyond Homo Faber, and have since lost the ability to use tools. Perhaps you can blame genes, upbringing, or the class system for the fact that some professional people don’t value practical skills, and worse still, they transmit this disinterest to their children.

So the folks in Cramond may have evolved to become more interested in reading highbrow novels about a shape-shifting petty criminal in Georgian London, or attending chamber music recitals in the Queens Hall, or become pre-occupied with the configurator on Range Rover’s website, trying to decide which combination of colour, trim and accessories they’d prefer when the time comes to replace their spaniel-scented Volvo estate. Regardless, it seems they have no manual dexterity when it comes to domestic repairs.

Once I got home, I unpacked the lamps from the box and disgorged a Sainsburys-bag-for-life, which was full of seemingly random grub screws, washers and nuts. I scrutinised the partly-dismantled uplighter body to see what needed fixing. Someone had already loosened the nuts which located the terminals for the linear halogen lamp, and in order to free the little casting the terminals were mounted on, they’d also loosened the large nut which holds the shade by clamping together a sandwich of glass, silicon gaskets and aluminium.

But then they’d evidently got stuck. The wires which feed the terminals have crimped connectors on the end which didn’t quite fit through the central hole. So they’d just chopped the connectors off! Fortunately, I already had a complete shade: using a pair of Lindström needle-nosed pliers, I gently compressed the metal tangs which held the crimps within the connector, then released the wires and guided them through the hole. I was able to swap the wiring and connectors between the uplighter bodies. Using the right tool, the job took five minutes.

Fixing the uplighter gave me a moment of intense satisfaction, as I’d probably saved it from the skip.

A few weeks later, a spring on the loft ladder gave up with a loud bang. I’d been running up and downstairs with rolls of Knauf Loft Roll 44, as I try to bring the house up to current day insulation standards. So far, I’ve laid 350mm of glasswool quilt behind the uprights of the roof structure where it tapers out to the eaves, and 150mm in the depth of the first floor joists along the centre. I had to lift about 60 square metres of chipboard deck before I could insulate that central part of the floor, though.

The loft ladder was made about 50 years ago by Ramsay Ladders in Forfar. In Scotland, the Ramsay Ladder has become synonymous with loft ladder: it’s a metonym, in the same way that “Hoover” and “vacuum cleaner” were once interchangeable. I drove up to Forfar and bought a pair of new springs, and the helpful maintenance chap at Ramsay Ladders explained how to fit them: I needed to loosen some fixings whilst keeping my knee on the end of the radius arm, otherwise the one with the good spring would rebound and break my wrist.

He asked if I’d replaced springs on a ladder before, then narrowed his eyes when I explained that I was an architect. I thought I’d reassured him that I knew how things went together; but his experience was that architects know more in theory than they do in practice. He shared his thesis that architects should spend a few months working on site during their training. They should spend time working with an electrician, then a joiner, then a bricklayer, and so on.

It’s a fair point. If you know how a building fits together in practice, it’s bound to improve how you design and detail. But that’s partly why the Year Out exists, so that students get some practical experience and also a feel for what the reality of building things is like. The flip side of that is that the Year Out can ruthlessly expose student architects who have no practical aptitude, and little interest in actually building things. At this point, they may realise that an academic career might be more suitable – and there’s no shame in that.

Thankfully, just like the little needle-nosed pliers in my tool box, I also have a set of Whitworth combination spanners, so replacing the Ramsay Ladder springs was straightforward. For a second time, I was pleased with myself – until I dropped the big plastic drawer which holds frozen loaves in the bottom of the freezer. The polycarbonate panel smashed, so I ended up having to buy a new one.  That’ll teach me to be judgmental about other folks’ lack of dexterity, because it proves that I’m a ham-fisted blockhead, too.

Neither does it bode well for my next task, which is to insulate the solum. But since the house was constructed with a gas-fired warm air heating system and underfloor ducts, I’ve got some hard labour ahead, because I've discovered that the ductwork is still in place in the solum crawlspace. You can imagine how much fun it will be to cut up the ductwork using a hacksaw, while lying on your side on a bed of bitumen and furnace ashes…

While legislators down south wrestle with how to implement Judith Hackitt’s Golden Thread, the aftermath of the Grenfell Tower fire is being felt in Scotland, too.

In her Building a Safer Future report, which was published in the wake of the fire at Grenfell Tower in London, Hackitt recommended the introduction of a “golden thread” to ensure that building safety is taken into account at every stage in a building’s lifecycle.  At first, it wasn’t clear how that would work in practice, but it turns out that the impact is far reaching.  Even though the requirements of the Scottish Technical Standards are seen as being slightly tougher than those down south, and the Building Control system here is more strictly applied than the third party verifier model used to date in England, they have lots of things in common.

Fundamentally, we buy the same materials and products manufactured by the same corporations and sold by the same merchants. Despite the fact we practice in Scotland and are not directly affected by Hackitt’s report, we’ve discovered that it's no longer enough to state that a material complies with the relevant standard. Now we also need to produce fire test certificates for everything we specify:

• Intumescent paint
• Fire-rated windows
• Fire doors, of course
• Sandwich cladding panels
• MF partitioning systems

I’ve always tried to avoid sandwich panels, due to their lack of fire resistance, the plastic foam insulation inside each one which is environmentally nasty thanks to the blowing agents used in its manufacture, and the near impossibility of recycling panels at the end of their life – but we’re sometimes forced to use them, to meet a client’s branding requirements. American motor manufacturing corporations even have a habit of specifying US cladding products which simply aren’t available here – and even if they were, they wouldn’t meet our standards because they haven’t been fire tested in the UK.

However the last category, MF partitioning, has proven to be the trickiest. Over the past two or three years, manufacturers have quietly re-tested and re-badged all of the walltypes in their White Book, Green Book or Pink Book.  Suddenly, internal wall constructions which we’ve used for years to achieve 60 minutes at 6 or 7 metres high, no longer comply.  As a result, all the internal wall constructions which we specified during the Covid era, marked up on the walltypes drawing, then detailed, have had to be revised. 

Where we can’t get Warrington fire test certificates for particular build-ups, such as the fire-resistant “umbrella” where a compartment wall head hits an existing sandwich panel roof, we needed to get fire engineering assessments which took much longer than we expected.  Then we discovered that one of the major plasterboard firms no longer markets horizontal Shaftwall, which is proved to be an acute hassle since it’s essential to form the fireproof lid over the fire escape stair enclosures, if you’re to avoid using wet trades and heavyside materials. So now we have a mix-and-match building, using systems from rival manufacturers, which won’t greatly please the contractor’s buyer.

I guess that’s one difficulty of working on refurbishments of modern commercial sheds, which I’ve had to do once or twice recently – rather than taking either an older industrial building with a concrete frame and brick walls, or designing a newbuild on a clean sheet of paper. The older industrial is bombproof: the frame and walls are inherently fire resistant and will achieve 4 or more hours of fire resistance, effortlessly. The newbuild can be engineered to do whatever’s required from the outset.

Unravelling the Golden Thread means that more product information is needed at an earlier stage of the scheme, and each Building Warrant application becomes a larger package which takes longer for the BCO to assess – and at the very end of the project, O&M manuals will grow to be two or three times their current size.  Architects, structural and fire engineers have to put together a narrative, telling the story of how they struggled to make relatively modern retail sheds and warehouses comply, and documenting the increasingly complex systems they needed to do it.  However, if that saves even one life, it's a price worth paying.

We're about to start investigating a high profile building with a failing roof, which I daren't name, even for the best of reasons. It's a piece of "iconic" architecture by a Big Name, and already I notice a touch of schadenfreude from people who always suspected that the Big Name didn't have the architectural firepower to detail junctions and penetrations or the nous to handle the weathering of complex surfaces.

So it proved, and a few years after completion the envelope appears to be staining badly, and leaking through rooflights and perhaps other joints and vertices too. It has an unusual form, but pure “form-making” is the preserve of second year students and paper architects; fabric design takes longer to understand and the further into practice I go, the more I realise I’ve still got to learn.

Part of the issue is that the building with the failing roof is a one-off in every sense. It’s an experimental prototype, probably the only building of that ilk the practice has designed, using systems and techniques they won't use again. It’s a Mark 1 building, when the client really needed a Mark 10 version with the detailing refined and all the problems ironed out.

So I come back to something I've written about here before, perhaps to the point of repeating myself.  An architect who doesn't master materials and detailing can never really be a fully-formed architect. If you don't know which material or system is appropriate for the form you’re drawing, all is lost.  You’re just like a would-be musician who hasn't progressed to read music, so plays everything by ear.

Until he reached his late 30's, my father was a commercial grower: firstly in a market garden producing flowers, fruit and vegetables for the wholesale market, then later in commercial landscaping where he was involved with nursery work and planting schemes.  As an aside, Dad’s career evolution showed me there’s hope for late developers: another example was Howlin Wolf, who was 42 years old when he signed to Chess Records.

The final project my father worked on before he shifted industries was the landscaping of the Scottish Amicable site at Craigforth on the edge of Stirling. Craigforth is about to be razed for redevelopment and I have conflicted feelings every time I drive down the A9: the trees and shrubs around the buildings are some of the last living links with my Dad, and that's particularly poignant at this time of year.

Hard landscaping was important at Craigforth and other projects he worked on in Dundee and Glenisla, but my father’s main raw materials were plants.  Three years ago when I sorted through things after he died, I found some old seed packets which he had set aside.  Not the A6-sized consumer packets with luridly colourful photos which contain around 20 seeds, but miniature brown paper envelopes, each little bigger than an old-fashioned railway ticket, but with four or five gross of seeds in each.

One packet was marked “Arkwright Ruby”. I had to look that up, and discovered it was an F1 hybrid Viola. An old-fashioned cousin of the pansy and the violet plant, it flowered for six months at a time, producing profuse, coppery-maroon petals. Dad had a connection to Carter’s Seeds of Raynes Park in London, but this particular packet came from Thomson & Morgan of Ipswich.

My father also had dozens of monographs dedicated to plants and plant families, and he kept a note of varieties, yields, successes and failures.  Seed packets along with diaries, leaflets, flyers and bulletins from the Ministry. By recording how well every crop did each year, he built up a record which became more detailed as the years passed. Each market garden, croft and farm has its own unique microclimate and soil, slightly different to those around it.  For that reason, textbooks can only be so helpful and beyond that point, empirical information is vital.

I don't think it's too stupid to suggest that architects should be this close to their raw materials, too.

How many architects can say they walked the context before designing a building, observing how well similar materials used on similar aspects have lasted?  Paddy Hislop at TRADA is a really helpful source of advice on timber cladding; for other materials you have to develop relationships with experienced suppliers.  That's how I learned about plywood, from one of the original directors of Rembrand Timber, who entered the industry just after the war when factories which made de Havilland’s timber aircraft were re-tooled for furniture and construction.

So before I even considered a form-making exercise, I’d make sure I really understood which systems were appropriate to achieve it – and after I’d built one, I’d monitor it in order to learn how to improve it the next time around.

Sometimes it feels like trying to resolve competing demands, like thermal performance against the limited depth available in a wall or deck build-up, is like trying to post an octopus through a Venetian blind.

The push to improve U-values has run all through my career. We scoffed at the buff-covered copies of the Building Regs which the greybeards had, prescribing walls which didn’t even achieve 0.45 W/m2K. The old-timers each had their own dog-eared copy, but when the new Technical Standards came in later in the 1990’s, the office only bought one copy and it came in a ring binder: all the better to swap pages out each time the thermal performance of walls and roofs became more stringent.

As values rose from 0.45 to 0.3 then 0.2 W/m2K, how best to achieve them became a concern, because material performance didn’t improve so insulation thicknesses just kept increasing. I vaguely remember 100mm kit walls, which soon became 140mm studwork, then 200 or 250mm JJI joists were used as studs to accommodate increasing depths of glasswool, cellulose or rock fibre.

As a result, we've always been up against it with wall linings and timber kit build-ups and rather like computers during the 1990's, as soon as processor speed and RAM increased according to the so-called Moore’s Law, the gain was more than absorbed by a more sophisticated programme carrying out ever more intensive tasks.

Similarly, despite pressure to move from glasswool and stonewool to polystyrene (EPS or XPS) polyurethane (PUR), then poly-isocyanurate (PIR) foams, which offer progressively better R-values: as soon as thinner insulation was developed, the minimum U-value improved too, so you needed more of it. The net gain in footprint won back was nil, because materials technology and the Technical Standards had fought themselves to a standstill.

However, what feels like one of the few genuine pieces of materials tech progress in recent decades has become a commercial proposition: Vacuum insulation, or more accurately evacuated insulation. As you may remember from the teacher’s explanation of the Dewar Flask in Higher Physics, a vacuum, or the absence of air, has no thermal conductivity and that makes it the perfect insulant. Nothing can pass through a vacuum apart from radiation, so no heat is lost to either conduction or convection.

Vacuum insulated panels (VIP’s) have been in use for a few decades in refrigeration plants, cold stores, cryogenic freezers and the like, manufactured by companies like Morgan Advanced Materials (the UK company which was previously known as Morgan Crucible). They’ve only made their way into the building industry in the past decade or so as firms like Kingspan and the German firm Va-Q-tec began production. Around 2005, VIP’s were introduced into the construction industry in Germany, Switzerland and Scandinavia, to begin with as deck insulation on balconies and other locations where deep build-ups cause detailing headaches.

VIP’s are made from fumed silica sand, which forms a porous matrix from which more than 99.999% of the air is evacuated. The silica is encapsulated in a vacuum-tight envelope made from aluminium foil, and the key thing is to make sure that isn’t penetrated by a nail or screw. In 2022 terms, silica is inert so it won’t harm the environment, and it’s not flammable so it won’t go up in flames, like foam insulation frequently seems to do.

In thermal performance terms, vacuum panels have a lambda value four or five times better than the best foam insulations, and one analysis demonstrated that a VIP board 20mm thick achieves the same thermal performance as mineral wool or PUR insulation board with a thickness of 185mm.

At the same time as VIP boards emerged, a new type of double glazing was developed.
Similarly to the ever-thickening walls conundrum, upgrading traditional sash and case windows to double glazing often means using bulky glazing units which ruin the fine lines of the transoms and astragals.

Vacuum glazing is similar to a double glazed unit in construction, except that it doesn’t have a gas in the cavity, it has a vacuum. That vacuum is far more effective than filling a 20mm cavity with a noble gas like Argon or Krypton, and therefore only requires a 0.2mm cavity - hence the unit’s thickness is greatly reduced. Some of the first vacuum glazed units to come to market are the AGC Fineo and the Pilkington Spacia; for example, a Super Spacia unit achieves 0.65 W/m2K, against standard 4+20+4mm double glazing which achieves around 1.2 W/m2K.

Thanks to vacuum technology, finally we have the potential to return to the slim glazing profiles and slender walls of the 1960's… and even more importantly, to use far less raw material in order to save much more energy, and in doing so to reduce the gross floor area of the building. That’s a triple win, and as a result you may not need to post your octopus through a Venetian blind after all.

Happy Christmas when it arrives. :-)

I’ve just seen an advert on TV for mail order food boxes: the soundtrack in the background is the song Enola Gay by OMD. The jaunty electronic pop tune is a tribute to, and lamentation over, the aircraft which dropped the first atomic bomb in anger. A strange choice for an advertisement, it’s almost as dissonant as the “advert” for itself which the BBC has been playing recently.

The climax of This Is Our BBC is a clip of Jimmy Reid explaining that “This is something for all of us.” Superficially, that’s what the BBC’s credo is, something for everyone in the UK. Yet I wonder whether the people who montaged all the video clips together have an inkling of what Jimmy Reid symbolises to folk north of the border. Reid took on the British Establishment, the System, the political machine, and won.

Some would argue that the BBC is the Establishment’s state broadcaster, and a po-faced one with an undeveloped sense of irony at that. So it would be rather amazing if the BBC imagined that *it* is a Jimmy Reid figure, swapping sides in 2022 to take on the Establishment in the form of a political elite which it has helped to prop up for the past century.

Meantime, I’m currently finishing off a project and yesterday was taken up with the laborious process of collating and uploading all the certificates needed for the CCNP, or “Construction Compliance and Notification Plan”. That includes an Emergency Lighting Installation Certificate, Electrical Installation Certificate, Fire Alarm Certificates, Air Testing Certificate, and CE marking on steel.

The biggest surprise came as I read the steelwork certificates. As I brought them together into one Acrobat file, I paused to read where all the steel originated. It was supplied by local stockholder, Brown & Tawse, whose HQ is just along the road at West Pitkerro, although they sourced it from much further away:

• Advance UCS’s from British Steel in Scunthorpe, a company now owned by the Chinese
• PFC’s from Celsa Steel in Cardiff
• CHS’s from Tata Steel in Corby, the plant which once belonged to Stewarts & Lloyds of Glasgow
• RSA’s from Liberty Merchant bar in Scunthorpe
• Smaller steel flats from Lamines Marchands Européens in Trith-Saint-Léger, France
• 152 x 152 UCS’s from Stahlwerk Thuringen in Unterwellenborn, Germany
• 254 x 254 UCS’s from ArcelorMittal Steel at Olaberria-Bergara in Spain
• Larger steel flats from Stahl Gerlafingen in Germany
• Rebar from Megasa Siderurgia Nacional in Maia, Portugal
• Handrail tubing from Çınar Boru in Turkey
• And finally, hot rolled steel plate from Hyundai Steel in South Korea

So despite Brexit, despite the Suez Canal incident last year, and despite calls to de-globalise, some of the steel has travelled several thousand miles. This matters, because imports cost money in fuel, import duty, and indirectly may end up funding people who we’d rather not support. No sign of Russia’s biggest steel producers such as Severstal, Evraz Group or Magnitogorsk Iron & Steel Works – but can you ever really know?

Of course, we used to make steel here in Scotland. The hot blast furnace was even invented here. But Corus has gone, and its predecessors too. Ravenscraig was an integrated iron and steel plant with the biggest hot strip mill in Europe. It was built by Colvilles, and if you work on older buildings, you’ll still notice that the webs of the beams are stamped Lanarkshire Steel Co. which was one of Colvilles’ subsidiaries.  The steel which Brown & Tawse used to supply was made a couple of hours down the road.

We used to make steel here in Scotland, but the Scottish steel industry didn’t have a Jimmy Reid to fight for it. So most of it was destroyed by Thatcher's henchman Ian MacGregor, and what remained, including the mills at Clydebridge and Dalzell were sold off to the lowest bidder. Now when we complete our CCNP, the certificates resemble the entries in a Eurovision Steel Contest.

Scotland, null points.

Although it sounds like a mix by DJ Tiesto, it's actually a description of the reflex hinge (sometimes called a "friction stay") fitted to most of today's top-hung and reversible windows.  Low stack refers to the depth of the hinge arms, Sinidex is a trade name and the Eurogroove is a standardised 18mm wide rebate in the jamb of the window frame. If the terminology means nothing to you, perhaps window specification is a more complex business than you realised...

At architecture school, I developed a hit-and-miss knowledge of windows from reading journals and occasionally picking up brochures and adverts from the trade press. In my first project at my first job after graduation, composite timber/ aluminium double-glazed windows were specified, and that was the starting point for a journey which gradually taught me about window technology.

Having previously specified NorDan, Velfac and Rationel windows on projects, a few years ago I spent a while collecting information then tried to compare the performance of all the composite window systems that were available in Scotland.  Recently I revisited the exercise for a new project, and some changes are obvious.  We've moved on from double glazing with low-E glass, and are on the brink of triple glazing becoming the standard.

Trying to find the perfect window? Sadly, it's like punching smoke. But unlike the DIY’ers, self-builders and internet wiseacres – architects have the advantage that we specify again and again, so we have some idea of how to measure success and failure. Plus we have access to proper technical resources such as BRE digests and TRADA research.  That's important, because the modern window is a high tech enterprise and in order to specify well, you need to know a bit about building science.

For example, the window frame sections consist of many-times-machined timber and complex extrusions, with drips, anti-capillary grooves and fixings for gaskets machined in. The angles of components, the gaps between them, and the geometry of the labyrinth which prevents rain being driven towards the interior, are carefully calculated.

During the 1950’s, the English Joinery Manufacturers Association developed the EJMA “Stormproof” window, where the casement is outward-opening and sits proud of and overlaps the frame. This standardised design with its “weather check” replaced the various styles of flush casement windows common until that point, and for the next 30 years or so house builders had a simple choice: timber frames of standard quality, eg, Magnet & Southerns “M4”, or timber frames of slightly better quality, eg, John Carr/ Boulton & Paul.

The stormproof window was adopted in Scotland, but Scotland is and always has been different to the south.  The lower temperatures and much higher exposure to wind-driven rain make our climate much more like Norway than Surrey.  We've fitted windows into rebated jambs and set them back further in the opening for hundreds of years, whereas the English Reg's still allow you to fit windows flush against the ingo of the outer leaf or brick skin.

When double glazing started to come in, partly driven by the Technical Standards and partly by replacement window firms such as Everest, the EJMA Stormproof window frame sections had to be beefed up in order to compete. The first Scandinavian windows I came across were in the timber clad, timber kit Moelven houses that Aberdeenshire Council built across the field from my grandfather's farmhouse in Kemnay.

A single-glazed window (as originally fitted to buildings in 1960’s) gave you an overall U-value (Uw) ~ 4.8 W/m2K, but a typical PVC-U double-glazed window from the 1980’s (4*12*4 with air space between glass) gave you Uw ~ 2.8 W/m2K. Almost twice as good. In a country where it feels like the last big innovation was the duplex sash and case window, that was big news. Of course, with traditional sash windows, effective sealing is always in conflict with the operation of the window. This means a traditional sash window is either airtight and hard to slide open, or easy to open but draughty.

Scotland and Scandinavia can be very windy, so their casement windows have traditionally opened outwards and they developed effective drainage profiles and sealants because wind and weather proofing is important. As I discovered during my research, Scandinavian expertise lies in top-hung reversible windows (using "H"-type or Spilka) gear, with double-glazing and noble-gas filled cavity to give Uw ~ 1.3-1.4 W/m²K, improving to 1.1-1.2 W/m²K with low-E glazing.

By contrast, windows from Austria and Germany are often inward-opening, but they do get extremely cold winters, so good U-values are judged more important and they pioneered thermally-broken frames and “warm edge” spacers to improve them. Austrian practice is to use tilt & turn rather than reversible gear, with an insulated laminated timber frame and insulated glazing bead, plus triple-glazing and noble-gas filled or vacuum cavity; even in the late 2000’s, they could achieve Uw ~ 0.65-0.7 W/m²K.

What’s state of the art now? 92 mm window frames, now with 48mm triple glazing (4*18*4*18*4), which provides Uw ~ 0.8 W/m²K. That’s the level set for new build Passivhaus buildings, along with EnerPHit renovations in the cold climate zone, ie. northern Scotland. To achieve that, windows and doors are fitted into reveals with all edges taped using flexible foil tape, and the reveals sealed with Compriband externally and silicone internally

If you think glazing units are like razor blades, where manufacturers keep adding more and more blades to the cutting head … you’re right. While researching this, I discovered that the Scottish company Enviro make Uw = 0.35 W/m²K quadruple glazing. As far as I’m aware they’re the first in the UK, no doubt others will follow. Meantime I’ll end with a series of cutaway images showing some of the different frame profiles available on the market today.

In some respects it’s surprising that they’re so varied, and that makes specification more difficult since you’re not able to compare Coxes with Mac Reds, but the main two types are Alu-clad timber windows where the aluminium acts only as an external finish (almost like a rain screen cladding) and Composite timber windows where both the timber and aluminium parts are structural.

Alu-clad timber windows:

Rationel Auraplus, Uw = 0.79 W/m²K and lifespan of 80+ years with 4*20*4*20*4 (made in Denmark)

NorDan NTech One, Uw = 0.8 W/m²K and lifespan of 60+ years with 4*12*4*12*4

Optiwin Resista Modern, Uw = 0.64 W/m²K

Allan Brothers Horizont/ Alu Clad, Uw = approx. 0.9 W/m²K

Broxwood Alu-clad Timber Tilt & Turn, Uw = 0.7 W/m²K (made by Arbo in Latvia)

Katzbeck Combina Passiv, Uw = 0.71 W/m²K (made in Austria)

Norrsken P41A

HON Quadrat Studio FB, Uw = 0.85 W/m²K (made in Czech Republic)

Viking SW14 Uw = up to 0.60 W/m²K (made in Estonia)

Composite timber/ aluminium windows:

Velfac 200 Energy, Uw = 0.82 W/m²K and lifespan of 60 years (with 48mm glazing) 4*18*4*18*3, Uw = 1.06

IdealCombi Futura+, Uw = 0.74 W/m²K (made in Denmark); 4*13*3*14*4, Uw = 1.04

Gaulhofer Fusionline 108, Uw = 0.65 W/m²K

Internorm HF310, Uw = 0.62 W/m²K

Silber Fenster Passive, Uw = 0.71 W/m²K

Neuffer Eco Idealu, Uw = 0.78 W/m²K

Green Building Store “Ecocontract Ultra” (made in UK); 4*18*4*18*4, Uw = up to 0.68 W/m²K

Footnote - As with my piece a couple of years ago about electrical accessories, this is written from my own personal experience, and neither I nor Urban Realm have links to any of the manufacturers. Copyright in all images rests with the respective manufacturers.

Sometimes publication of a book traps an entire world in amber.  In this case, The Information Book isn't Martin Amis's novel of a similar name, but a glimpse into Scottish architectural practice during the 1930's.

John Burnet trained at the Ecole des Beaux-Arts during 1870’s.  Afterwards, he joined his father's practice Burnet Son & Campbell, and later established his own in Glasgow with a second office in London set up in 1905, after Burnet won a commission to design the Edward VII galleries at the British Museum.

One of Burnet's key assistants on the project later became a partner: Thomas Tait studied at Glasgow School of Art under the Beaux Arts teacher Eugene Bourdon (after whom the ugly brown brick building on Garnethill is named).  By 1910, Tait was a leading member of Burnet's staff, and played an important part in the design of the Kodak Building in London, considered to be among the first examples of modern architecture in the UK.  

Tait worked for a time in New York and was a highly skilled perspectivist, but is best remembered nowadays for Tait's Tower at Bellahouston Park, part of the 1938 Glasgow Empire Exhibition. Other notable works include St. Andrews House on Calton Hill in Edinburgh and Hawkhead Hospital in Paisley, along with many projects in London. 

The third leg of the partnership was Francis Lorne, who was by all accounts a skilled manager and also became the spokesman for the practice, arguing that Modern architecture required “a change of heart … only by getting back to architecture as a practical building problem for our own country, our own people, our own climate and conditions of life, can we produce an architecture that will mean something.”

The firm became Burnet, Tait & Lorne in 1930, and the expat Scots working from Glasgow and London grew into the leading British architectural practice during the 1930's, in a way that wasn't repeated until RMJM's glory days of the 1960's.  Big cities are full of opportunity if you're in a position to seize it, which Burnet, Tait & Lorne were able to do during the inter-war period.

It was Francis Lorne who wrote the book “Architectural Office Administration” in 1921, then a decade later pulled together The Information Book of Sir John Burnet, Tait and Lorne, which should be better known as it's the prototype for the New Metric Handbook, The Architect's Pocket Book and pretty much every other guide to design practice which followed.

Today The Information Book is the best work of reference for 1930’s and 40’s era buildings in Scotland, and the rest of the UK. It’s coloured by the dual influence of North American practice in steel-framed medium-rise office blocks which was particularly influential in Glasgow, plus the Art Deco and Moderne buildings erected in London between the wars which prefigured full-blown Modernism.

Its genesis is described in Christian Barman in the book’s Foreword (for greatest effect, read out loud in your best imitation of Miles Cholmondley-Warner):

“The need for a great compendium of information first impressed itself on me some five or six years ago, when I had not long taken over the Editorship of Architects’ Journal.  The more the task was studied, however, the more difficult it seemed. … The thing was just about as much as a commercially produced periodical, however well intentioned, could ever dare to consider.
 
“Then, one day, good luck brought a sudden and, I feel, a most happy solution.  Chancing to be at the house where my friends Thomas Tait and Francis Lorne maintain their finely staffed office in partnership with Sir John Burnet, RA, I saw a draughtsman coolly turning the pages of the book of my dreams. … It did not need a close scrutiny of the Information Book to convince me that it was a very superior specimen of the kind of thing I had myself been trying to bring about.”
 
First published in 1933 by the Architectural Press, in the days when that was run by the splendidly-named Hubert de Cronin Hastings, The Information Book begins with a couple of chapters on the Secretarial Department and Draughting Department.  These describe what we’d now call practice management, and are followed by a series of 147 Information Sheets which cover everything from construction details, brick and board sizes, terminology and electrical symbols to extracts from the Building Regulations. 

 
It may have begun as an in-house guide to Burnet Tait & Lorne’s office standards and procedures, but The Information Book became universally useful, and Lorne wasn’t the only one to think that a book like this could be handy.  In 1932, “Architectural Graphic Standards” appeared in the US, and twelve editions later it’s still in print and has developed into a doorstop-sized handbook of typologies, ergonomics and design data.  Similarly, Architects' Data, universally known as “Neufert”, was first published in Germany in 1936, and after many German editions it was translated into English in 1970 and published by Lockwoods.
 
The simultaneous emergence of these three books demonstrates that the 1930’s was an inflection point, where the Modern Movement and its modern methods of construction became properly mainstream.  Structural steel and concrete frames were being widely adopted, so our day-to-day knowledge had to extend beyond traditional building techniques.  As Barman says in his introduction to The Information Book, “It only seems the other day that the main facts about building science could still be got between the covers of a book of average size”.  No longer. 
 
Neither Neufert nor the later New Metric Handbook tries to cover as much ground, from practice management to design data, as The Information Book ­- but during the intervening forty years so much extra information has come into the world that an architectural “book of everything” would be a massive tome.  As it is, Neufert weighs 2kg.

 
Reference works such as The Information Book and its cousins were essential in the pre-internet world.  I entered practice at the changeover, when CD-ROM’s and early webpages had begun to supplant technical books.  But we still hung on to brochures and supplements which included priceless information, like the Corus steel sections booklet or Pilkington’s glass guide.  They provided a safety blanket of reassurance, even if you rarely needed to consult them.
 
Today, Burnet Tait & Lorne’s Information Book is a reminder of two things: firstly that the state of the art eventually becomes a quaint curiosity lurking in an antiquarian’s back room; yet the book also retains some usefulness. It’s one of the few places where you can see how buildings from the 1930’s and 40’s – of which there are hundreds of thousands still standing – were put together, and how we went about achieving that.

ps. Note to book dealers researching their catalogues - please credit me and link to Urban Realm if you find the information in this piece useful. :-)

Searching for a taste of the exotic? 100 years after Modernism began, more or less, with the founding of the Bauhaus, there’s a conventional palette of materials which we still use. Scotland’s traditional materials like rubble masonry, red deal, slate and harling were supplanted early in the 20th century by beton brut, engineering brickwork, blonde timber and stainless steel. They’re still widely-used, even though none are particularly modern any more.

But Modernism had another strand, exemplified by the Barcelona Pavilion and Aalto’s private house commissions in Finland. Those used a richer palette of leather, darker timbers, bronze and marble. Many of the projects which feature in glossy design magazines today still use this “luxury” palette. No MFI kitchens and laminate flooring for them…

At the moment, I’m working on a range of projects including a centre for people with autism, an aviation academy and a Grade A fit-out for corporate lawyers. As you’d expect, the first one conforms to strict guidelines, the aviation project has an engineering bias, and the lawyers lean towards a sombre palette which is radically different to what the computer games developers in a nearby block wanted.

The lawyers’ office suite looks out over the firth, and the internal doors are finished in a veneer which has parallel stripes of very dark brown to black, alternating with lighter bands of golden brown. At first I thought it might be Zebrano, but having consulted the Architect’s Giant Bedside Book of Exotic Veneers, I think it’s actually Macassar Ebony.

Some use “Macassar” for any Ebony with prominent light and dark streaks, but it’s generally acknowledged as Diospyros celebica. Both Zebrano and Macassar veneers came into fashion a few years ago, but remain in the timber trade’s highest price group. For example, Range Rover use Macassar for dashboard and door cappings, even though their Chief Designer, Colour and Materials, Amy Frascella suggested in an interview I read that there’s a shift in favour of reclaimed and non-leather materials in what she calls post-industrial colours.

That might mean vegan-friendly polymers and fake “pleathers”, plus sustainably-sourced timbers or even post-consumer recycled material. For example, waferboard, strandboard and OSB are different names for the same thing, a board pressed from sawmill waste. Carbonfibre is another possibility, at least in sports cars, and various man-made luxury textiles such as Alcantara.

Natural materials have different advantages, but in all conscience some timbers are difficult to spec, because tropical hardwoods grow very slowly. Teak and Mahogany were popular in the 1950’s and 60’s, but that popularity meant swathes of rainforest were felled and we began to seek alternatives, such as Sapele and Jatoba. Yet timber is only truly sustainable if you plant a tree every time you chop one down – and if you’re prepared to wait for several generations before you harvest that patch again.

As I was hunting for a match for the Macassar wood, I spoke to several veneer suppliers, one of which was located in the East End of London. The cheerful Cockney technical rep decided to have a word in my shell-like, as Arthur Daley would say: “That looks like a laminate rather than a veneer, mate – an expensive high pressure laminate, but it’s a laminate nonetheless.” Cheers, geezer.

It makes sense when you understand the context. Macassar Ebony is rare in veneer form because the trees don’t grow particularly tall, so finding boles large enough to cut door-sized sheets of veneer from is difficult. The small sheet size makes the veneer more suitable for cabinetry, inlay work and making musical instruments. Macassar is also a tropical hardwood, which while not listed in the C.I.T.E.S. Appendices of endangered species, it’s definitely on the I.U.C.N. Red List of vulnerable trees.

The trees are native to the Celebes Islands in the East Indies and they’re named after the Indonesian port of Makassar, which was the main point of export. They’re also found in Maluku and Borneo – although back in the day, many shipments came through India and Sri Lanka. Until the 1970’s, Holt’s Blue Funnel line ships called at the less well-known ports of Sumatra, Java, Borneo and often took on cargoes of exotic hardwoods. Nowadays, due to the trees’ rarity and our concern about the sustainability of tropical hardwoods, Ebony is rightly difficult to get hold of.

It was always thus. Ebony wasn’t readily available in Europe until the 1600’s, although the Greek historian Herodotus records that Ethiopia paid an annual tribute of 200 ebony logs to the Persian Empire. After the 17th century, woodworkers in France perfected the craft of veneering with ebony for furniture and cabinetry and even today, France cabinetmaking is called ebenisterie and a cabinetmaker is known as an ebeniste.

So that explains why Macassar laminate is an acceptable substitute for the real thing. After speaking to the cheerful Cockney, I called up Herodotus on the blower - but he was out of stock, and anyhow doubted whether he could get veneer into the country due to the Brexit Effect. So the moral of this story is that we’re in the market for a convincing laminate, weighing the efforts of Formica, Egger, Resopal and Polyrey.

The best match so far comes from Formica, which captures the colour and tone of a real Macassar Ebony, as well mimicking its texture. Whether or not the lawyers realise it, their choice of door finish is a modern facsimile of an exotic tree which is amongst the aristocracy of timbers. In fact, we covet Macassar wood, and its rarity, so much that we’ve almost logged it into extinction.

If you’re searching for a microcosm of Brexit Britain, you could do worse than begin by scrutinising the UK’s widget manufacturers.  Over the past few weeks, I’ve scoured the wholesalers on Dryburgh industrial estate for well-designed electrical widgets, or “wiring accessories” as M&E engineers call them.

As I hunted through trade outlets and online, my path crossed with some Buy British enthusiasts, who are on a mission to support the UK economy at this difficult time; shades of Al Murray’s Pub Landlord and his campaign to Save the Great British Pint… So this is a rumination on whether we make stuff any more, and if so, whether it’s any better than what we import.


Buy British is sometimes overtaken by the imperative to Buy Scottish, but there are a few exceptions.  You’d think that with two of the UK’s Big Six energy suppliers based here – Scottish Power is headquartered in Glasgow and Scottish & Southern Energy in Perth – there would be a thriving electrical components industry in Scotland?  Sadly, no.


Scottish firms concentrate on the heavy end of electrical engineering: Brand Rex at Glenrothes make cables, Belmos in Motherwell make distribution boards, Parsons-Peebles at Rosyth build electric motors, Bonar Long in Dundee used to make power transformers and Mitsubishi Electric at Livingston still makes air conditioning and heat pumps.  However, we appear to have neglected the well-designed, good quality switchplate.


“The door handle,” said Juhani Pallasmaa, “is the handshake of a building.”  Presumably the light switch isn’t far behind.  It’s another point of close contact, yet many switches are made from white moulded plastic, which looks cheap, feels cheap and isn’t made to last.  Neither is there any thought given to its environmental impact – so we should listen to Dieter Rams, the German industrial designer about whom a documentary film was released recently.


Rams was Braun’s chief designer from the late 1950’s to the mid 1990’s, and in that time he designed hundreds of products which we’d now call minimalist.  He wasn’t a stylist, but approached each product ergonomically, so that it would be well made, long lasting and intuitive to use.  


Dieter Rams has been talking about the social, political and environmental impact of design for more than half a century – interestingly, the antithesis of the line taken by late Isi Metzstein, who complained that too much consideration is given to the social and operational aspects of design, as opposed to the architectonic.


Many of the products Rams designed for Braun were made from injection-moulded plastic, which isn’t in the least environmentally-friendly.  However, he and his contemporaries didn’t make disposable goods, they made things to last: lots of people have Braun products such as calculators, radios and kitchen gadgets which still work, 30 or more years after they were made.  30 years or more can’t be said for cheap light switches.  


It’s rarely worth trying to repair white moulded plastic faceplates when they break, and they can’t be recycled either.  Similarly, manufacturing in the Far East then shipping components to Britain is madness, no matter how cheap it is today to stick things in a container.  So, bearing in mind environmental impact as well as aesthetics and practicality, the following thoughts come from my experience as a specifier who insists on seeing and feeling samples, and also from listening to electricians and electrical engineers.


Where to begin?  I’m told that in the 1960’s, Crabtree accessories were robustly made, albeit rather old-fashioned and chunky in appearance.  Then MK Electric produced a slimmer, sleeker style of faceplate which became more popular.  However, sockets and switches from the 1970’s and earlier were made from ivory Bakelite, which is pretty much bulletproof, whereas the moulded urea-formaldehyde plastic used by everyone since then is easy to crack.


Recently, a spark took me aside to ask why architects specify MK Logic Plus so frequently.  He felt it must just be habit, because while MK Logic accessories used to be "Made in UK", MK was bought by Honeywell a few years ago, and some of its products are now "Made in Malaysia".  Their website does say, “MK Electric, unusually for the sector, still manufactures its products for the UK in the UK; with a factory in St Asaph as well as Southend.”  The electrician complained that he often had to return MK accessories to the wholesaler, because the fixing screws were jammed solid against the terminals, and he blamed that on manufacturing in the Far East.  Perhaps that's just prejudice, though.


Which makes would he recommend?  Hager, Contactum, Schneider.  Doing a bit of digging, “In the UK, Hager has a well-established R&D team and global resource to meet the needs of the market. This is backed up by the UK factory.”  Contactum, “is one of a few remaining manufacturers of electrical wiring accessories and circuit protection products in the UK, and manufacturing still continues today at its factory in Cricklewood, London.”  We'll come to Schneider later.


The electrician reckoned that Telco, LAP and Knightsbridge were firms to avoid; according to him they are cheap and appear to be made abroad.  So perhaps there is a correlation between where a thing is made and its quality.  Is that economic nationalism, “common sense” as Al Murray’s Pub Landlord might put it, or pure prejudice?  Many of us are cynical about the quality of imports – in other words, we believe that these things could be made much better than they are.


Personally I used to reach for the MEM catalogue as my default for white accessories – MEM Premera faceplates appeared to be decent quality, looked slim, and a full range of accessories is available.  MEM is now owned by Eaton, an American corporation, which shut down its factory in Oldham in 2005.


But compared to white plastic, metal faceplates win every time.  They’re not manufactured from petrochemicals, they won’t shatter like plastic does, they don’t turn yellow with age, and “live” finishes such as bronze will develop a patina with use, which we find attractive.  Finally, if we’re finished with them the metal can be recycled rather than going to landfill or incineration.


Metal faceplates got a bad rep in the 1980’s when there was an outbreak of Victorian Brass in suburban Britain.  Once that subsided, polished chrome became popular, and now in theory you get a brass, bronze, chrome, stainless steel, nickel or copper finish, as well as powder-coated or clear polycarbonate “invisible” switchplates.  Most of the major accessories firms offer several ranges in metal, and after some research I discovered that quite a few still manufacture them in the UK.


Wandsworth Electrical produce a “premium designer electrical socket which is 100% designed and made in Britain.”  Focus SB sell “Quality Electrical Accessories Made in Britain: we are the only UK company licensed to manufacture electrical accessories for export to China.”  So it isn’t all one-way traffic.  Similarly, Hamilton Litestat have a Union Jack on their website and offer “largely UK-made products”; M. Marcus manufacture all their accessories at a factory in Dudley; and according to G&H Brassware, “All our products are hand assembled at our premises in the West Midlands.”


But the best-designed products I’ve come across were made in Britain by GET Group.  Their sockets and switches were presented in a box with a translucent sleeve which slid back from the carton to reveal a switchplate which followed the same design ethos as the keys on a MacBook’s keyboard.  The plate’s corners were neatly radiused, the rocker edges were rounded off and their action was a well-damped clunk, rather than the nasty click-clack of a £2.50 switch.


GET’s accessories were made from steel and brass and high density polymer, and even came with M3.5 screws in two different lengths, to suit different depths of backbox.  That level of design thinking is rare, especially at the consumer end of the market.  Electricians liked their robustness and the ease with which the terminals could be wired; I guess architects liked their aesthetic, bearing in mind that they were Mac-like, and of course Apple designer Jonathan Ive was heavily influenced by Dieter Rams … so ultimately the widget makers could learn from Rams' design approach and sustainable philosophy.


GET Group plc was swallowed up by Schneider Electric of France a decade ago, and their clever designs have gradually disappeared, which is a great shame.  It’s not clear from Schneider’s website whether they still manufacture in the UK, either.  That adds to the feeling that well-known firms have been taken over by overseas companies, production moved offshore, and the quality may suffer while the brand trades on its past reputation. 

On the other hand, the contract quality fittings which architects specify for higher end projects are quite different to the budget quality you find in B&Q, Homebase et al., and the former are still made in the UK, if not Scotland.  They might incorporate sophisticated electronic dimmers, or bespoke finishes which use metalworking skills developed by locksmiths and ironmongery hardware makers in the Black Country.  


In conclusion, the future seems to lie in making high value products, yet there doesn’t appear to be a design-led electrical accessories firm in this country any more.  Perhaps James Dyson will take up the challenge, having already launched his own ranges of taps and lights …

A while ago, I wrote about the Beech Starship, a business aircraft which looks like an artefact from a future civilisation.  By contrast, the DH103 Hornet fighter appears hopelessly old-fashioned – yet it reached almost 500mph in level flight, which made it the fastest piston-engined aircraft of its day.  It could cruise at the speed of today’s jet airliners, and outran the first jet-powered fighters.  The chances are, if you took a Hornet to the air races at Reno in Nevada today, it would out-run all the souped-up Mustangs and Sea Furies, setting a new absolute speed record.


In many senses, the Hornet was the piston-engined aircraft perfected.

A few weeks ago, the BBC showed a documentary about Eric “Winkle” Brown, the Scots-born test pilot.  As a naval aviator, he set a record for the number of landings on aircraft carriers which has never been beaten, and when in his unassuming way Brown describes the Hornet as the favourite from all the different aircraft he flew, that means something.  Captain Brown has flown more types of aircraft than anyone else in history.


Eric Brown is a top candidate for the Most Interesting Man in the World.  As a schoolboy, he attended the 1936 Olympics in Berlin and met a WW1 flying ace.  During WW2, he escaped from the wreckage of a torpedoed ship, helped to liberate Belsen and took 2,000 enemy prisoners armed only with a pistol – not to mention a few close calls where he had to abort and promptly GTFO using a parachute.  After the War ended, he interrogated leading Nazis including Hermann Goering, aircraft manufacturer Ernst Heinkel and designer Willie Messerschmitt.  Brown was the first man to fly a jet on and off an aircraft carrier, and he set aviation records that will almost certainly never be broken.


The de Havilland Hornet was his favourite, "For the simple reason it was over-powered.  This is an unusual feature in an aircraft, you could do anything on one engine, almost, that you could do on two.  It was a 'hot rod Mosquito' really, I always described it as like flying a Ferrari in the sky." The Hornet was the fastest twin piston-engined operational combat aircraft in the world while in service, and the first aircraft to demonstrate a cartwheel manoeuvre.

"For aerobatics the Sea Hornet was absolute bliss. The excess of power was such that manoeuvres in the vertical plane can only be described as rocket-like. Even with one propeller feathered the Hornet could loop with the best single-engine fighter. I had felt such absolute confidence that I was mentally relaxed … Indeed, there was something about the Sea Hornet that made me feel that I had total mastery of it.”

"In my book the Sea Hornet ranks second to none for harmony of control, performance characteristics and, perhaps most important, in inspiring confidence in its pilot. For sheer exhilarating flying enjoyment, no aircraft has ever made a deeper impression on me.”

At the root of any aircraft’s design is the equation which resolves power, weight, lift, drag and trim into performance.  In simplistic terms, power makes an aircraft climb whereas attitude varies its speed.  The Hornet’s high rate of climb came thanks to the Rolls-Royce Merlin, arguably the engine of the 20th Century, which in this case developed more than 2000hp from 27 litres of swept volume.  Just like the Mosquito, the Hornet had a pair of Merlins but in this case they were faired into streamlined “power eggs”.



The Hornet’s top speed is partly the function of a low co-efficient of drag arising from a sleek fuselage and a laminar flow wing; this thin wing was made possible by new materials.  The Hornet’s long range came thanks to its light weight; both strength and light weight derived from de Havilland’s early mastery of composite construction.



During the 1930’s, aircraft structures evolved from doped fabric stretched across an ash frame, to the geodesic spaceframe of steel tubes which Barnes Wallis used in the Wellington bomber, and eventually to all-metal stressed skin structures.  De Havillands went their own way, searching for a different method of achieving strength and lightness.  They settled on timber, but rather than a load-bearing timber frame (like a Morgan car or a timber kit house) they developed the first composite monocoque.



Unlike the Beech Starship, a revolutionary aircraft which used carbon composites, the Hornet wasn’t a great leap into the unknown; it’s an evolutionary aircraft, albeit one at the very apex of its line of evolution.  De Havillands had been working on composites for a decade before the first Hornet took flight - although their initial objective was to build stronger, lighter propellers.



In order to cope with more powerful engines, propellers had grown in diameter, gained more blades, and their tip speeds were approaching the sound barrier.  As a result, the centrifugal forces at the propeller hub had increased to the point where there were many catastrophic failures.  De Havilland Propellers worked with Aero Research at Duxford to overcome the drawbacks of laminated timber props, successfully using phenol-formaldehyde resin in the manufacture of propellers.  The attraction of this material was that, with a density of around half that of aluminium alloy, centrifugal forces at the root were greatly reduced.



De Havillands was a rare aircraft company which made everything for itself.  Piston engines were built at Stag Lane in Edgware, then jet engines and later rocket motors plus of course complete aircraft at Hatfield, Leavesden and later Hawarden.  As a result, it was able to cross-fertilise materials research between propellors, wings and fuselage design.



The work on propellers “spun off” into fuselage and wing structures for the (almost) all-timber Mosquito, which the wartime Press christened the Wooden Wonder.  The Mosquito was built from sandwich panels consisting of thin skins of plywood veneer bonded to a core of end-grain balsa wood.  The core functions just like the web of an I-beam while the plywood skins function as the flanges.  The sandwich panel's bending stiffness is proportional to the core thickness, in the same way that an I-beam becomes stiffer as the web deepens.  Doubling the core thickness yields a panel roughly six times stronger and 12 times stiffer.



At a time when other WW2 combatants were desperately trying to smelt cobalt, vanadium and other rare metals into exotic alloys, it seems bizarre that de Havillands were in the market for balsa wood.  You can only assume that German spies put this down to British eccentricity, if they even remarked on it at all, yet Baltek’s sawmills in America struggled to keep up with demand.  Today the technology seems so accessible; hobbyists and model-makers have access to the same plywood veneers, balsa wood and epoxy glues that de Havillands used.


Plywood was a relatively new material, and also a composite, with plies of different thicknesses and orientations providing degrees of strength and stiffness.  As well as de Havilland themselves, the Mosquito was built by Roe, Gloster, Phillips & Powis and even Venesta – the forerunner of Venesta Cubicles which is still in business today.  In 1937 their "Venesta" plywood and "Plymax" metal-faced plywood made them an ideal choice as fabricators of ply composite aircraft such as the Mosquito. 

The Mosquito was built by the furniture industry, which was mostly based around its traditional centre in Buckinghamshire: incidentally, that’s the reason High Wycombe was one of the most heavily-bombed London suburban towns. The industry had a long history (Defoe mentions it) in the town and in the 1940’s there were still many local manufacturers. The Windsor chair was its most famous product, but practically every other sort of furniture was also made. Components for the Mosquito were reportedly produced by Marples and G-Plan, and supplying the materials was a multi-national effort: the frames used Alaskan spruce and British ash, the sandwich used 3-ply Canadian birch plywood and Ecuadorian balsawood.

The DH103 Hornet evolved from the DH98 Mosquito - and as is the way of things, it became lighter, faster, more powerful and stronger. Both aircraft used variations of a pre-formed plywood monocoque shell strengthened with spruce stringers and constructed using high-strength synthetic bonding resins.  This technique had been pioneered on the famous DH.88 Comet racers, and would also be used to great effect on the Dragonfly light twin and the Albatross airliner of 1938.  One step forward from the Mosquito was the way de Havilland built the Hornet’s wing spars, and another was the wing surfaces themselves.



Mosquito wing spars have all-wooden tension and compression booms, but this would have been impossible for the Hornet, because of the large cross-section of wood necessary for the more highly-loaded wing.   The problem was overcome by making the tension booms from aluminium extrusions, and using wood for the spar webs and compression booms.  A layer of veneer was bonded to the aluminium parts then everything was assembled to form a spar of remarkably low weight and high strength. 

Moulded wood veneers of a type that we’d now term cross-laminated timber were combined with more conventional parallel layered glulam to produce spars of amazing accuracy and complex geometry.  Tapered and kinked spars with “L”-shaped sections were formed using this technique, which was originally developed for manufacturing Isokon furniture.  Isokon is well known in architectural circles, thanks to the Lawn Road Flats designed by Wells Coates…

The Hornet’s wings comprised an aerofoil with a composite wood and metal internal structure, with a stressed birch-ply double upper skin and an under surface of reinforced “Alclad”.  This was the first time that aluminium had been bonded to timber in a structural fashion.  Lift acting on the Hornet’s wing meant that the metal skin on the underside of the wing went into tension, and the ply-balsa composite went into compression – so the materials’ inherent qualities were used to best advantage.



The idea of combining skins of ply and aluminium with a lightweight core was a conceptual leap born of on a new generation of synthetic adhesives.  De Havillands’ composite structures relied upon a new epoxy resin developed by Aero Research.  This glue, “Redux 775”, was developed in 1941 as the first modern, synthetic structural adhesive for metals - and it was first used in the Hornet Mk1 which was built at Hatfield.  Hornet construction, like that of the Mosquito before it, used similar techniques as modern fibreglass wet layup.  The positive mould was covered with wax, then strips of thin veneer were laid up in different directions to improve the tensile strength in all directions, just as today you would lay up glass or carbonfibre mats.



The first skin would be covered by a sandwich layer of balsa wood, followed by another layer of veneer.  Metal fittings were embedded in the wooden layers and a low voltage applied to heat the resin electrically, which speeded up curing.  Once everything was dry, the fuselage or wing half would be removed from the mould then after installation of some formers, cables and wiring, glued to the other half.  Finally the fuselage would be covered in another layer of thin wood, covering the glued joint, then covered in aircraft linen, doped and painted to improve aerodynamic smoothness.



In 1948, de Havillands acquired an aircraft factory at Hawarden Airfield near Chester: it was used to build and assemble the Hornet Mk3, while other parts were manufactured at the firm’s factory in nearby Lostock.  Incidentally, Hawarden is now called Broughton, and after de Havilland became part of Hawker Siddeley it developed sophisticated wings for their airliners: today, it builds every wing for every Airbus airliner, and is owned by GKN.  The “N” in GKN stands for Nettlefolds, and when the Hornet was in production they had several huge factories in the Black Country, stamping out millions of cross-head screws an hour.  Today, GKN uses carbon fibre to build composite aero-structures which owe a great deal to the principles that de Havilland developed three quarters of a century ago. 

The Hornet’s fuselage was built in two halves which joined together on the centreline, so called “egg carton” construction using cold moulding to form the curves.  This monocoque structure gave the fuselage a high degree of redundancy which meant that the aircraft could sustain terrible damage yet keep flying.  Many Mosquitos returned home missing large chunks of wings, fins and control surfaces, shot away by enemy cannon fire.  Timber composites also avoided the hidden dangers of metal fatigue, which de Havilland fell foul of with their Comet airliner during the 1950’s.



Without the work of Aero Research and de Havilland Aircraft during the 1930’s and 1940’s, it’s arguable that there would be no plywood composites or structural adhesives, hence the SIP panel and the JJI joist wouldn’t exist, either.  It’s also worth noting that the Beech Starship, which was hailed as revolutionary in form and construction, isn’t as original as I implied.  The Starship was also built in two halves, and epoxy resins were also used to bond its composites together.  Just like de Havillands, forty years before them.


Although it marked the apex of de Havilland’s piston engine development, there’s no sense in which de Havillands developed a Pygmalion-like relationship with the Hornet.  Even as it first flew in 1944, the firm was already building jet-propelled aircraft, so the Hornet’s career was cut short.  After the DH98 Mosquito and DH103 Hornet, De Havilland’s plywood-balsa-plywood sandwich was later used to form the fuselage of the Vampire and Sea Venom jets. 

De Havilland refined the assembly process: steel bands were latched onto heated jigs with quick release toggles, to ensure smooth fuselage cross-sections.  Adhesive curing cycles were carefully instrumented and automated.  Smaller glue-laminated components such as the engine intake ducts used thin timber strips which were cold-formed on jigs to tight radii.  Nonetheless, the Hornet's gift to us all is composite construction, which the designers of racing cars, airliners, yachts, buildings and even fridge freezers take for granted.



The late Martin Pawley was fascinated by these technology transfers, and the crossovers between architecture and other fields.  As a columnist in the AJ, BD and so forth he wrote about the design of tube trains, cars and aircraft – seeing them as complementary to architecture.  He recognised the truisms that racing improves the breed, and war pushes technology forwards faster than peace.  While this bandwagon was passing, I thought I'd jump onto it…



Pawley was in tune with the spirit prevailing during the late 1980’s and early 1990’s, when Richard Horden built a series of houses using off-the-shelf components from racing yachts, then Rogers and Foster completed a series of buildings which borrowed from the automotive and aerospace industries, such as neoprene gaskets and super-formed metals.  This climate gave birth to a thousand architectural dissertations about Lotus sports cars, Slingsby sailplanes and McLaren's F1 operation. 

Unwittingly, they echoed a pattern from 50 years before, when wartime firms desperately hunted around for peacetime outlets once hostilities ended.  De Havilland were fortunate, as their focus shifted readily from military to civilian aircraft.  Venesta gave up flying and came to specialise in toilet cubicles and IPS systems.  Others were not so lucky.



What about the legacy of Ronald Bishop, who designed the Hornet?  He should be remembered for helping to win the War using pioneering materials: but today it seems that War means rousing musicals, martial style (smart uniforms never go out of fashion) and the cult of the Great Man.  Our superficial treatment of that era ignores Bishop and his counterparts Barnes Wallis, RJ Mitchell and Roy Chadwick who were responsible for the Wellington, Spitfire and Lancaster respectively.  They were complete designers, in the sense that they harnessed materials science, structures, aerodynamics, manufacturing techniques as well as considering damage tolerance and repairability. 

They also had a sense of purpose which is difficult for us to grasp now: they were part of Churchill’s enormous enterprise which stretched from shadow factories making widgets to the invention of operational research. 

The sadness is that no Hornets survive at all today, although there are rumours that an entire squadron was dismantled and buried under an airfield in Malaysia when they became surplus to requirements.  It seems unlikely that anyone will disinter them, but you never know…

Some images used here are courtesy of the Hornet Project website, which has temporarily disappeared from the web.