Did you know that the thickness of the insulation will affect the thermal performance of your roofing system?

Insulation thickness has to be taken into account to meet the requirements for building regulations. Please refer to the Thermal Performance Guidance Sheet for indicative U Value for associated thicknesses.

Requirements in England

Based on Approved Documents L Volume 1 and Volume 2 (June 22).

New Build – Best Starting Point	Existing Building – Extension	Existing Buildings – Refurbishment
0.11	0.15	0.16

New Build – Best Starting Point	Existing Building – Extension	Existing Buildings – Refurbishment
0.14	0.18	0.18

Requirements in Wales

Based on Approved Documents L1A, L1B, L2A and L2B

New Build – Best Starting Point	Existing Building – Extension	Existing Buildings – Refurbishment
0.11	0.15	0.18

New Build – Best Starting Point	Existing Building – Extension	Existing Buildings – Refurbishment
0.14	0.18	0.18

Requirements in Scotland

Based on the Technical Handbooks published by the Scottish Governments Building Standards Division (BSD). (2015)

Domestic.

New Build – Best Starting Point	Existing Building – Extension – A*	Existing Building – Extension – B*	Existing Buildings – Refurbishment
0.09**	0.13	0.18	0.25

*Column A is for extensions where the existing dwelling’s walls and roof U-values are worse than 0.70 W/m²K in the walls and worse than 0.25 W/m²K in the ceiling. Column B is for other extensions, upgraded existing thermal elements, non-exempt conservatories and conversion of unheated buildings.

**It is understood that the best starting point U Value has changed from 0.10 to 0.09 in February 2023.

Non-Domestic.

New Build – Best Starting Point	Existing Building – Refurbishment, Extension & Conversion of Unheated Buildings	Existing Buildings – Conversion of Heated Buildings
0.14	0.15	0.25

This document is a guide to assist in the production of documents. It is the responsibility of the client to seek further guidance and approval from Local Authority Building Control regarding target U Values prior to the commencement of works. Nothing in this document or any other literature produced by or on behalf of Polyroof Products Ltd is to be regarded as constituting a contract binding in law between Polyroof Products Ltd and any customer. The only contract which Polyroof will enter into is that contained in the Polyroof guarantee which takes effect only when issued in writing by Polyroof to the customer. Specimen guarantees are available on request.