In Scotland, cladding is subject to more stringent regulations.
Introduction and background to the regulatory changes
Earlier this year, I published an article in which I discussed the fact that the 2020 editions of the Domestic and Non-Domestic Technical Handbooks, official guidance for compliance with the Building Scotland Regulations 2004, had removed direct reference to a party’s ability to demonstrate alternative compliance with the Regulations by using a solution based on British Standard 8414 and BR135, which was previously included in the Handbooks.
The future of the alternative compliance route
The BS 8414 and BR135 path was still open to applicants at the time, and I wondered whether the removal of a direct mention to it in the Handbooks could be the first step toward the elimination of the alternative route entirely. I was wrong, and the route remains open today. The Scottish Government has stated that this is their aim with the publication of The Building Scotland Amendment Regulations 2022, which will change the Regulations, and that only stringent compliance will now be permitted under the new regulations.
Stricter controls on external wall materials
Materials will be subject to stricter controls. When the modifications take effect, the Regulations will require that any materials that form part of an external wall cladding system are of European Classification A2-s1, d0, or A1, classed in accordance with BS EN 13501-1:2018, be used in the construction of the exterior wall.
Buildings affected by the new cladding requirements
These limits will apply to all residential high-rise buildings as well as other high-risk structures such as hospitals and care homes. In Scotland, the term high-rise refers to any structure that is 11 metres or more in height, rather than the 18 metre threshold used elsewhere in the UK.
Removal of the BS 8414 fire testing loophole
If cladding systems had passed a large-scale fire test in accordance with British Standard 8414, they might previously have avoided the need to comply with these stricter material requirements. This allowed combustible materials to be used in an external walling system, provided the system as a whole passed the fire testing process. This route has now been closed.
Prohibition on metal composite materials
A further provision of the amended Regulations is the outright prohibition on the use of highly combustible metal composite material in the construction or renovation of buildings of any height. This introduces a complete ban on Grenfell-style cladding, which consists of panels made up of two metal sheets with a filler core.
Understanding the calorific value threshold
If the core has a gross calorific value greater than 35 MJ per kg, it can no longer be used on projects in Scotland. Gross calorific value measures how much energy a material contributes to a fire. For comparison, diesel has a calorific value of around 45 MJ per kg, while dry firewood is around 16 MJ per kg.
Criticism of the scope of the ban
Some commentators argue that the prohibition does not go far enough. By limiting the ban to only the most combustible class of metal composite materials, critics suggest an opportunity to improve overall safety has been missed. The restriction also applies only to metal composite materials. Other potentially hazardous products, such as high pressure laminate materials, fall outside the scope of the ban.
Potential for future tightening of regulations
It will be interesting to see whether these restrictions become more stringent over time, in the same way as previous controls on combustible cladding for high-rise buildings.
Implementation dates and next steps
The amended Regulations will apply to all projects where a Building Warrant application is submitted on or after 1 June 2022. Updated editions of the Domestic and Non-Domestic Technical Manuals reflecting the new regime will be available online in early May.
