It has come to the notice of FIS that there is a potential issue where fire stopping is being installed around cPVC pipes.

Some fire stopping mastics have been found to react with the cPVC pipes leading to costly remedial work and disputes.

FIS’s recommendation is where two or more systems come into direct contact, ensure that the system owners have been informed and that written evidence is supplied confirming their compatibility and long-term suitability.

This Compatibility between pipes and fire and acoustic seals fact sheet provides more details about this issue and guidance to avoid other issues when working with reactive (intumescent) seals.

Please contact FIS Technical Director Joe Cilia if you have any questions at

FIS maintains a technical team who work with the industry to set standards and to support members, specifiers and clients and works to raise quality in the sector. Full details and content can be found at