The Building Regulations & Approved Document B Wales - Flat Roofs

In this article we will look at the following:

The requirements for flat roof insulation in Approved Document B Wales
When a roof should be considered a wall
The requirements for specified attachments (for example balconies unheated on both sides)
Which Kingspan Insulation products can be used

The information contained within this article should be used in combination with the full Building Regulations.

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What guidance does Approved Document B give for insulation in roof applications in Wales?

The limitations on roof coverings as set out in Table 5 of ADB1 and Table 16 of ADB2 should be followed and the roof system should be classified to EN 13501-5. Roof constructions are classified as B_ROOF(t4), C_ROOF(t4), D_ROOF(t4), E_ROOF(t4) or F_ROOF(t4).

B_ROOF(t4) is the highest (best) performance, and F_ROOF(t4) is the lowest (worst).

The guidance details separation distances (the minimum distance from the roof, or part of the roof, to the relevant boundary) by the type of roof covering and the size and use of the building.

A table showing the requirements for roofs in Wales

In order to meet these requirements, the full roofing system is tested. The most commonly used approach to testing the roofing system uses test method CEN / TS 1187: 2012.

Alternatively, roofs intended to be fully covered by inorganic materials, listed as per Commission Decision 2000/553/EC of 6th of September 2000, implementing Council Directive 89/106/ECC can be considered to fulfil the external fire performance requirements without the need for testing. These are:

loose laid gravel ≥ 50 mm or ≥ 80 kgm2 (size 4-32 mm);
sand/cement screed ≥ 30 mm; or
cast stone/mineral slabs ≥ 40 mm.

Note that complying with the guidance in the Approved Document does not guarantee that building work complies with the requirements of the regulations. There may also be other ways to comply with the requirements than those described in the Approved Document. The project Principal Designer (during design stages), Principal Contractor (during construction) and relevant consultants (such as Fire Engineers) should be consulted to ensure compliance with the Building Regulations.

When is a roof considered a wall?

Note that any part of a roof pitched at an angle of more than 70 degrees to the horizontal (if that part of the roof adjoins a space within the building to which persons have access, but not access only for the purpose of carrying out repairs or maintenance) is considered part of the wall and must comply with Regulation 7(2). Regulation 7(2) sets the requirements for external walls and specified attachments in relevant buildings.

Wall insulation used in relevant buildings above 18 m must achieve European Classification (Euroclass) A2-s1,d0 or A1.

Take a look at our article on relevant buildings for more information.

What are specified attachments and how should they be insulated?

Specified attachments are defined in Regulation 2 and include balconies attached to an external wall. Therefore, balconies (an attachment to a wall unheated on both sides), also including attached and inset balconies, would need to meet the same requirements as walls. Terraces and roofs however (with a heated space below) are exempt. For more information, please refer to BS 8579: 2020 (Guide to the design of balconies and terraces).

Wall insulation used in relevant buildings above 18 m must achieve European Classification (Euroclass) A2-s1,d0 or A1.

Take a look at our article on relevant buildings for more information.

Which Kingspan Insulation roof products could be used in Wales?

Any of the Kingspan Insulation roofing products that form part of the roof system could be used on roofs provided the roof covering / system meets the requirements of the table above or are used in a build-up intended to be fully covered by inorganic materials, as detailed above.

Systems incorporating our flat roof insulation products can achieve B_Rooft4. Performance is reliant on the roof covering, therefore for further details please contact your roofing system supplier or waterproof membrane manufacturer.

Balconies that are unheated on both sides are considered a specified attachment and need to comply with Regulation 7(2) and, therefore only K-Roc Flat Roof Slab 70/039 (Euroclass A1) could be used.