Mark Chalmers

I was down in London a few days ago, wandering around and taking photos during the heatwave.  I arrived at Stansted the day after the tower block at Grenfell Tower caught fire, picking up snippets of news as its awful consequences began to unfold.

I stayed near Hogarth’s House in Chiswick, an antiquarian remnant which sits hard against the A4 dual carriageway.  William Hogarth died 250 years ago: just along from his former house is a huge roundabout named in his honour.  The house is cloistered within a little walled garden; the traffic roars past it day and night.  These are the contrasts you find in every city, but in London they’re magnified.  An 18th century Hawksmoor church sits in the shadow of a 60-storey glass cheesegrater; a Tudor cottage lies under the flightpath for Heathrow.  Social housing in London also throws up marked contrasts.

One day, I visited the post-war schemes at Lillington Gardens, Alexandra Road and the Barbican, each of which dates from the same era as Grenfell Tower.  The Barbican is always impressively well-maintained, while Lillington Gardens is covered in scaffolding at the moment while refurbishment takes place.  Lillington Gardens and Alexandra Road are medium rise, and they pack in a reasonably high density while still feeling generous.  The Barbican consists of every housing typology you could imagine, including three tower blocks.  Architecturally, it’s still the most impressive housing scheme in Britain.

The fire at Grenfell Tower is the flip-side of that.  It seems like an echo of Ronan Point, another London tower block which suffered a catastrophic accident almost 50 years ago.  At Ronan Point, a gas cooker blew up in someone’s kitchen, and the explosion broke out, causing the large precast panels which made up the tower’s structure to cascade like dominoes.  A few years ago, in a different magazine, I wrote about George Fairweather, the Dundee-born architect who predicted in the late 1960’s that something would go disastrously wrong with a system-built tower block.

Fairweather was chosen in 1962 to chair the committee which would draw up a new Fire Code to govern the safety of tower blocks, which had stretched up beyond the reach of the Fire Brigade’s turntable ladders.  Six years after Fairweather wrote the code, a student working for him went to see a block of system-built flats in Greenwich.  As he discussed the construction with her, it became apparent that when the concrete panels didn’t fit, a labourer attacked them with a sledgehammer until they did.

“Mark my words,” said George, “one day one of these bloody things will fall down just like the Tay Bridge.” His words turned out to be prophetic.  Ronan Point, and dozens of other blocks built using the Anglian system, didn’t comply with the Fire Code which Fairweather had drafted.  It seems likely that the fire regulations for high rise buildings will have to be re-thought again, after Grenfell Tower.

The Building Regulations in England differ in detail from the Technical Standards in Scotland, but the principles are similar.  Both sets of fire regulations cover means of escape, building separation, internal compartmentation and also the structure and cladding of buildings.  While the Building Research Establishment is “working around the clock” testing samples of cladding taken from tower blocks across the country, Eddie Mair on Radio 4 struggled to translate what they’re testing - surface spread of flame, core flammability, and so forth - into lay peoples’ terms.

The comprehensibility of cladding fire resistance is a bit like the difficulty the popular press has had with the Edinburgh Schools investigation.  The wall ties which link an outer leaf of blockwork to the structure behind it are just bendy bits of metal.  The job they do is self-explanatory – they tie the wall together – but if you walked onto a building site, they would be the last thing you would spot, bundled on the scaffolding or poking out of the coursing.  A cartoon drawing of a wall, and a reporter holding a piece of metal would simply and quickly explain what’s allegedly missing from dozens of buildings.

Similarly, everyone knows about fire, we have a prehistoric attachment to it … but without an architectural background, it’s not easy to conceive how fire spreads nor how you make buildings fireproof.  Many tower blocks were built using precast concrete systems, similar to Ronan Point.  In Scotland quite a few were built using reinforced concrete frames and masonry cladding, both of which are inherently fire-resistant.  Others, like the Red Road flats in Glasgow, were steel-framed and clad in various types of panel.  Some panels are fireproof, others are sheathed in rockwool insulation or layers of mineral board.  All of the different types were designed to meet the contemporary Building Regulations.

Intuitively, Radio 4 listeners may think that brick and concrete will protect you from fire better than thin composite panels could – yet a few years ago I visited a gas research station with a stair tower clad in 9.5mm thick Cape “Durasteel” panels – which provided 4 hour fire resistance.  Thickness is no guarantee of fire-proof-ness.  Similarly, when is 30 minute fire resistance not 30 minute fire resistance?  If you read the small print of a fire test certificate, you’ll notice the caution that a half-hour fire door may not last for 30 minutes in a particularly large, hot fire – although it may last long enough to protect someone escaping from a flat.

At first, the fierceness of the flames at Grenfell Tower and the speed with which they spread suggested that a rising gas main had caught fire.  Hydrocarbon fires have far more energy than cellulosic fires, and the burning rates of gas, petrol or chemicals are much higher than wood, paper and textiles.  Looking at the European standards for fire testing, the fire curve of a cellulosic fire reaches 500°C within five minutes and rises to 945°C over time.  A hydrocarbon fire is fuelled by oil or gas and reaches a flame temperature to 1000°C almost instantaneously after ignition.  The difference between an instant and five minutes may be the time it takes to escape from the building.

It quickly became clear that something at Grenfell Tower was releasing huge amounts of energy, which in turn caused the fire to spread rapidly across the building, but at first no-one guessed that the cladding was feeding the fire.  After all, the Building Regulations stipulate the flammability of building materials; section 2.6.4 of the Technical Standards is the appropriate place to look if you want to see what’s acceptable in Scotland.  Yet even a major fire in the building fabric is survivable, if you can get people out of the building quickly enough, and ensure they don’t breathe in any toxic smoke.

Just how far the regulations have progressed since tower blocks were built in the 1960’s and 1970’s is underlined by the difference between Grenfell Tower and high rise buildings constructed in the past few years.  London’s older residential towers appear to have only a single means of escape – one central stairwell – and apparently many of the internal doors aren’t fire-rated, either.  New tower blocks usually have two or more means of escape, the front doors of the flats are 60 minute fire-rated to form a smoke lobby between the flat and the escape stair, smoke ventilation is provided in the fire escape route, and the flats themselves are fitted with sprinklers and smoke detectors.

Most of these provisions kick in when a building exceeds a certain height: the cut-offs for enhanced fire measures are 7.5 and 18 metres.  The topmost storey of low rise buildings is less than 7.5m above ground level, medium rise buildings are between 7.5 and 18m, and high rise are 18m or more.  Those heights are based on the maximum height a fire tender’s ladders could reach (7.5m), and the maximum reach of an old-fashioned turntable-ladder appliance (18m).  These are thirty or forty years out of date: the fire service now has hydraulic platforms which can go up twice that height.

Usually, modern high rise buildings also have a fire-fighting lift.  When the alarm goes off, the passenger lifts are programmed to return to the ground floor and park with their doors open, so that residents don’t try to use them to escape.  However, one lift within the bank is a specially reinforced, fireproof lift which the fire brigade can use to head upwards and fight the fire.  Coupled with a dry riser or wet riser which they can plug hoses into, it means they don’t have to pull a charged hose up fifteen flights of stairs.

Although the inquiry into the fire hasn’t even begun, we know the implications of Grenfell Tower will be far-reaching.

Yesterday, the company which makes the “Reynobond PE” panels used to clad the block decided to stop selling them for high-rise applications.  A spokesman for Arconic (which was formerly Alcoa, the Aluminum Company of America) said, “We believe this is the right decision because of the inconsistency of building codes across the world and issues that have arisen in the wake of the Grenfell Tower tragedy regarding code compliance of cladding systems in the context of buildings’ overall designs.”

Arconic’s factory in Merxheim, France, manufactures several types of Reynobond for the European market: Reynobond PE consists of polyethylene sandwiched between two aluminium skins, but other variants include a fire-resistant version known as Reynobond FR.  In the aftermath of Grenfell Tower, it’s likely that all sandwich panels will be scrutinised closely.  In particular, the use of low-flammability cores, as opposed to cores which are completely inert or fire-resistant, will be questioned.  Local authorities have already begun evacuating some tower blocks, and stripping the cladding from others.

The apparent lack of smoke lobbies between the escape stair and the front doors of flats may be another factor which inhibited people trying to escape from the fire, as smoke rose up through the only means of escape.  It may be that tens of thousands of internal doors need to be upgraded, and smoke ventilation installed.  Similarly, old tower blocks lack the automatic fire suppression systems (sprinkers) which new high rise residential buildings are fitted with as standard, and critically, many older buildings don’t have automatic fire detection systems which sound an alarm throughout the building if a fire is detected in one part of it.

One final point is that the Fire Officer can carry out an inspection then demand that fire precautions are improved, but one of the tenets of the Building Regulations is that they can’t be applied retrospectively to existing buildings.  Maybe that will change, in the aftermath of Grenfell Tower.