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The National House Building Council (NHBC) has stopped accepting a controversial means of clearing cladding for use on buildings.
In response to the Grenfell Tower fire NHBC, which says it carries out building control services for 80% of new homes built, has changed its policy to stop accepting so-called ‘desktop studies’ for cladding.
A desktop study allows a manufacturer to take data from previous tests on cladding and use those results to make a judgement on how a new untested cladding system would react to fire.
These have been called into question since the Grenfell Tower fire, with a spokesperson for the Ministry of Housing, Communities and Local Government telling Inside Housing there had been “inappropriate and irresponsible use of these studies”.
Neil Jefferson, chief operating officer at the NHBC, told Inside Housing: “At the moment, I think most leading building control companies are only accepting option one and option two [non-combustible cladding or a full-scale test]. We’ve led that and we’ve done the same thing. So that has changed.”
He added that while previous desktop studies are “not now unacceptable”, there has been an “acceptance that things needed to change.”
The NHBC is an ‘approved inspector’ – a private building control company introduced by Margaret Thatcher in 1985 to compete with local authorities.
Though their role has been greatly diminished by privatisation, local authorities still carry out some building control work.
Paul Everall, chief executive of Local Authority Building Control, told Inside Housing: “There is a current government consultation on the use of desktop studies in relation to cladding. We have not issued any advice to our members on their use in advance of the outcome of that consultation.
“In the light of Grenfell, all of our members are of course aware of the need to study very carefully any building control application which comes before them relying on desktop studies in support of the cladding material proposed, and to ensure that what is said does not extrapolate beyond the limits of the tests referred to.”
The government has said it is consulting on whether desktop studies should be banned completely.
Its submission to the European Commission for this consultation, however, makes no mention of the possibility of a ban.
Building regulations say cladding systems which contain combustible insulation must be shown to meet specific standards based on “full scale test data”
A ‘desktop study’ is a means of making an assumption about whether or not a cladding system would meet these standards without actually testing it.
It involves using data from previous tests of the materials in different combinations to make assumptions about how it would perform in a test.
This is not specifically provided for in the current guide to building regulations, but the government believes they are loosely drafted to an extent which makes it permissible. It plans to redraft the guidance to include specific rules on the use of desktop studies for the first time.
The alternatives to a desktop study are full scale testing or not using combustible materials.
People are concerned about the process because it is based on assumption: at least one system cleared through a desktop study has failed a full scale test.
This is important for fire safety because mistakes may mean unsafe cladding systems being cleared for use on tall buildings.
Read our in-depth investigation into how building regulations have changed over time and how this may have contributed to the Grenfell Tower fire:
Inside Housing is calling for immediate action to implement the learning from the Lakanal House fire, and a commitment to act – without delay – on learning from the Grenfell Tower tragedy as it becomes available.
We will submit evidence from our research to the Grenfell public inquiry.
The inquiry should look at why opportunities to implement learning that could have prevented the fire were missed, in order to ensure similar opportunities are acted on in the future.