A1 and A2 Rated Building Board Guidance

Bauder are seeing more and more instances where building boards with A1 or A2 reaction to fire classifications are being used for roofing applications, particularly for upstands.

Why are we sending this update?

The reason for this update is that we are increasingly finding situations on site where a building board is being used for upstands and sometimes decks without third-party approval confirming the product is suitable for use in flat roof applications.

There are many different types of A1 and A2 rated boards and they do not all have the same properties. Correct product identification and verification of what is actually being proposed is essential.

Who takes responsibility for specifying these boards?

By changing a material specification to include alternative components, the authorising party assumes design liability for the construction.

There is a duty of care on the part of the designer to ensure that any alternative components are fit for purpose, compatible with other components, and approved for use by all manufacturers and suppliers who would issue a warranty for the flat roofing system and/or its components. Failure to do so may invalidate warranties.

What issues can occur using the wrong type of product?

The following issues are examples that Bauder have encountered to date; however, this list is not exhaustive:

• Mechanically fixing insulation, where achieving secure fixings can be problematic.
• Fixing the top leading edge of the capping sheet, where secure fixing can again prove difficult.
• Fixings corroding due to the incorrect type of fixing being specified or installed.
• Boards being left exposed and absorbing moisture, which can lead to membrane de-bonding.
• Boards that are not suitable unless fully supported being used in inappropriate applications.

Which is the most suitable board type to use?

Cement-Bonded Particle Board appears to be the most suitable option for flat roof applications.

We have attached a document to this update which has been produced through a cross-industry collaboration between SPRA, LRWA and NFRC. This document should be used as guidance when determining which board types are suitable and which are not.

GUIDANCE FOR THE USE OF BUILDING BOARDS WITH A1 OR A2 REACTION TO FIRE CLASSIFICATIONS IN FLAT ROOFING

If you have any questions, please do not hesitate to contact me.