What have we learned?
Speaking at the Tall Buildings Conference, Ian Doncaster outlined what we have learned about the principles of smoke control in high-rise blocks of flats.
The fires at Grenfell Tower and Lakanal House were a wake-up call for the UK in terms of fire and smoke behaviour, said Ian Doncaster, Managing Director of Fire and Smoke Solutions. Although there have been examples around the world of rapid fire spread from combustible cladding, we never quite expected something of that scale in the UK.
Doncaster outlined the regulatory landscape of smoke control in England and Wales. It began with the CP3 guidance document, which was based on studies of post-war residential blocks. On the back of further government-funded research at BRE, this evolved into Approved Document B which we know today.
There is then a host of standards which impact on the design and installation of smoke control systems and associated measures in high rise residential blocks. These include:
But since Lakanal House and Grenfell Tower, “everyone has had to sit up and take stock”, said Doncaster. Positive steps forward are being made, and we can expect more regulation and guidance on the back of the Grenfell Tower inquiry. These steps include the Building Safety Act; the London Plan Policy D12; single stair buildings, where the debate is changing for new builds; and stay put, where the question is: Should people still be able to evacuate safely if they want to do so?
The options for smoke control in high-rise residential buildings today are between stair pressurisation, lobby extract and hybrid fire engineered systems. Designers must select the right design principles for a particular building. Pressurisation systems can provide greater protection for stairs, but tend to be more expensive and involve bulkier equipment. Designs are based on certain assumptions – for example, which doors are open in the event of a fire – so a model is only really a view of reality which may not actually happen.
In terms of whether systems should be capable of fire service operation or operate automatically, Doncaster’s view is that as systems can look and behave quite differently, the human factor should be removed as much as possible.
In terms of the opportunity for self-evacuation, the debate comes down to who can self-evacuate in certain circumstances. This depends on individuals’ physical strength and mobility to deal with issues such as air pressure on doors.
Finally, maintenance of smoke control systems has to be carried out by competent people, as we’ve all heard about systems that don’t work because of incorrect installation or maintenance.
Legacy high-rise residential blocks were generally made of concrete, built to the standards of the time, and were generally “safe when constructed”. The main method of smoke control was manual cross-ventilation, but this often meant problems with wind noise. The building stock has since evolved due to issues such as maintenance, damp and faults, the green agenda, increased expectations, “beautification”, and ill-thought-out changes. All this means that these buildings have become less safe than when built, or are less safe by modern standards.
The issues affecting legacy buildings include privatisation and mixed ownership, tenants’ responsibility for work/section 20 notices, buy-to-let influences, developer and builder responsibilities, commercial interests and quantifying the length of ‘legacy’.
Around 440,000 people live in tower blocks, but what can we do about the inadequate ones? asked Doncaster. The options include a waking watch and evacuation alert systems. Retrofitting is never an easy option but is sometimes necessary.
In summary, homes should be safe, secure and stable, and we need to learn from history and strive for better. Systems to protect escape routes from smoke must be functional and well maintained, but restoring or upgrading buildings to an acceptable level will require persistence, commitment and budget, and specialist input is needed for smoke control system design, installation and maintenance.
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