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The Regs: Current guidance on cladding post-Grenfell

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Geoff Wilkinson looks at the government’s guidance on cladding pending the Grenfell Inquiry and Hackitt Review

The issue of cladding has been much in the news since the tragic fire at Grenfell Tower last June. There has been a lot of debate and conflicting advice since then and the matter was raised in Parliament at the beginning of this month (6 March).

This is because the Approved Document (AD) can potentially be read in different ways depending how you define cladding. To provide clarity post-Grenfell the Government has issued guidance that the AD should be read as allowing two basic forms of showing compliance -– either full-scale testing or the use of materials of limited combustibility. This brings the guidance in line with the wording of BS 9991, which was revised in 2015. As these routes are quite limiting, the use of desktop studies has become common since the publication of the Building Control Alliance guidance note 18 in 2014 gave a third option.

The Ministry of Housing, Communities & Local Government (MHCLG) has now set up a working group to review the validity of this third route and make further recommendations in future. However, pending the outcome of this review, architects are already finding that insurance premiums are increasing and they are being asked questions at renewal. These include ‘Do you follow the guidance set out in the Building Control Alliance (BCA) Guidance Note 18?’ and ‘If using option 3, do you ensure any fire engineers report is supported by test data from a suitable UKAS-accredited testing body and ensure these tests are suitable [sic] referenced in the report?

Architects therefore face a huge dilemma during this period while test certificates are re-assessed and the use of desktop studies is clarified. Do they quickly switch to specifying MHCLG-approved tested products (often with significant weight and thickness implications), or wait for the eventual outcome of the guidance and testing?

There have been conflicting press releases from various manufacturers about the performance of their products

Immediately after the fire, the government set up a building safety programme with the aim of ensuring that all high-rise residential buildings are safe from the threat of fire. It conducted a series of screening tests, to identify buildings with similar – and, potentially, unsafe – cladding. At the same time, the Building Research Establishment (BRE) tested different combinations of cladding and insulation to see which complied with the Building Regulations guidance. The consolidated advice was published last autumn, confirming the results of those tests, which showed that some combinations passed, while others failed. The BRE has also published a catalogue of past BS 8414 tests to assist architects in choosing compliant materials. The findings are summarised in the table below.

Despite this, there have been conflicting press releases from various manufacturers about the performance of their products and the validity of the government’s programme. For example, Kingspan has recently stated that the government’s tests were based on a 20mm gap between FR Cored ACM panels resulting in a pass for stone wool insulation but a fail for Phenolic insulation. However, when retested with a 10mm gap between the panels both forms of insulation passed, suggesting that very minor variations (often within accepted site tolerances) can make or break the validity of these assumptions.

So any decision on specification of cladding is ultimately one that needs to be made by the full design team and with the client’s buy-in as well, as it is the client who will bear ultimate responsibility going forward. Any decisions should be clearly documented and run past both your own professional indemnity insurer and the client’s buildings insurer.

In this respect, the Hackitt Report has identified the need for a golden thread that preserves the understanding and details of the initial design assumptions so that a seemingly minor change in the future (such as, for example, the gaps between panels) can be considered against those assumptions. 

This is a role that many may feel should be performed by the architect and would ensure that they are retained (in at least an advisory role) during the construction phase to ensure that the design intent is not lost. If you agree, you might wish to write to the Hackitt review to express that opinion. The review team can be contacted at: BuildingRegulationsandFireSafetyReview@communities.gsi.gov.uk

Geoff Wilkinson is managing director of Wilkinson Construction Consultants www.thebuildinginspector.org

This article originally appeared in the March issue of AJ Specification

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Readers' comments (1)

  • Geoff,

    Your: 'The Building Regulations Approved Documents set out two basic forms of showing compliance: full-scale testing, or use of materials of limited combustibility.'

    Why are you towing the absurd government line that AD B2 12.7 covers the outer cladding, whereas it obviously doesn't, as is immediately apparent even from the heading 'Insulation Materials/Products', as well as from the text of the clause itself.

    Andrew

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