Warranty Position Regulatory Position and Guidance Exemptions Does B4 still apply?
Green indicates we consider our position best practice and not in dispute Grey items cover the December 2018 Amendments, Approved Documents and MHCLG's own FAQs and advice notes Green indicates that the item IS exempt from Regulation 7(2), in accordance with Regulation 7(3) Green indicates that B4 still applies, and refers to relevant parts
Yellow indicates our position has the potential to be subjective   Red indicates that the item is NOT exempt. Refer to Regulation 7(3) Red shows that B4 no longer applies


Warranty Position

Definition: Waterproofing / damp proofing membrane materials installed in walls between ground level and DPC level. DPC's typically installed a minimum of 150mm above external ground level.

Vertical water proofing membranes should achieve a minimum of combustibility class B-s3, d0.

However, noting that membranes are an exempt material and Approved Document B is guidance: In this instance, if the height of the membrane strip is kept small, it is unlikely that B4-(1) could be shown to have not been met by using a Membrane that was not combustibility class B.

Also, noting that the membrane would require both heat and air to combust. If the membrane is trapped between a non-combustible insulation and a non-backing wall air will not be available.

Requirement: If a vertical waterproofing membrane that is not combustibility class B is proposed, then an Assessment confirming compliance with B4-(1) is required.

Note: MHCLG's January 2020 update "Review of Ban on use of combustible materials…." is currently consulting on whether to expand the exemption of the use of water proofing and insulation material from below ground level to up to 250mm above ground level.

Is the position indisputable? This may not be the view of all organisations.

December 2018 Amendment

Section 2 Reference: None.

Reference titles: None.

Approved Document

Reference title(s): None.

References: None.

MHCLG FAQS / Advice Notes

Reference: Section 4.

Reference title(s): Approved Document B volume 2 paragraph 12.14 a. provides further guidance on membranes and provides that they should achieve at least Class B- s3, d0.


Is the item exempt from Regulation 7(2), in accordance with Regulation 7(3)?: Yes.

References: 7(3)(g).

Statement: Membranes.

If exempt, are there any restrictions on the use of the system, component or material given in the guidance in ADB vol 2: Approved Document B clause 10.15(a) states "Membranes used as part of the external wall construction above ground level should achieve a minimum of class B-s3, d0."

Does B4 still apply?

Yes: Reference: B4-(1)

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Disclaimer: The information in this document is believed to be correct in light of information currently available and at the time of publication but is not guaranteed. Neither LABC Warranty nor its agents can accept responsibility in respect of the contents or any events arising from the use of the information contained within this site. The guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. For the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty Technical Manual.