When do I need to use non-combustible insulation?

When do I need to use non-combustible insulation?

Non-combustible insulation is any insulation that achieves an A1 or A2 fire rating when tested to BS EN 13501-1.  Examples of non-combustible insulation are mineral wool or cellular glass insulation.  There are several scenarios as set out in regulatory documents such as Approved Document B and Building Bulletin 100 which call for non-combustible insulation to be used.  We are going to explore all these scenarios in this blog.

Client requirements

Not something that will come up in any regulatory documents, but important, nonetheless.  Often clients may decide they want non-combustible insulation to be used for any number of reasons.  Even if the reasoning is beyond you, the clients’ requests should be honored as long as they don’t cause a breach of regulation.  For example, it is important to ensure that upstand heights of 150mm are still achieved.

Balconies

As dictated in Approved Document B a balcony is considered a “specified attachment” and therefor is part of the external wall meaning that it is subject to the ban on combustible materials.  The ban applies to “relevant buildings” which are buildings that meet the following criteria:

• The building is over 18m tall
• The building has one or more dwelling, an institution or a room for residential purposes
• The building is new or undergoing a material change of use.

Roof Upstands

Non-combustible insulation is required when insulating an upstand on a “relevant building”.  To best explain when non-combustible insulation must be used on upstands, it is probably easier to explain when combustible insulation can be used.   Anything outside of these limitations requires non-combustible insulation.  Combustible insulation can be used if it:

• Does not extend more than 150mm above the finished roof level
• Is not thicker than 60mm
• Does not span across a compartment wall line
• Is not against a habitable space

Compartment Walls

According to Approved Document B, thermoplastic insulation materials must not be used on the roof deck directly above a compartment wall and for a minimum of 1500mm either side of the compartment wall on residential buildings a maximum of 15m tall.  This outlaws insulation such as PIR and XPS meaning non-combustible materials must be used.

Bailey Can Help

If you're still not sure if you need to use non-combustible insulation on your flat roof or have any other queries regarding thermal regulations for flat roofs, get in touch with our technical experts you will help guide you in the right direction.