The use of cross-laminated timber in buildings taller than 18m looks set to be outlawed as the government reveals details of its combustible materials ban.

The amendment to Approved Document B, which was laid before parliament yesterday, has ruled out the use of any material within an external wall that does not have one of the top combustibility ratings, A2-s1, d0 or Class A1, with the exception of membranes, seals and gaskets.

The document defines an external wall as “anything located within any space forming part of the wall”.

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