Canopy flashings & weathering details

Severe driving rain is a common occurrence in the UK and these days even sheltered locations may be subject to high levels of deluge. Flashings and cavity trays offer a way around this problem, but should they be provided to canopy roofs?

Site-formed canopies

Where a site-formed canopy is constructed to provide weather protection to an external door a lead flashing (or a suitable alternative) should be provided at the junction of the canopy roof and the external wall. This will help to prevent premature failure of the materials. The flashing doesn’t have to link to a cavity tray provided there’s a cavity tray immediately over the external door opening.

Prefabricated (GRP) canopies

Where a prefabricated (GRP) canopy is used, the manufacturer may only require a silicone seal between the back of the canopy and external wall to reduce rainwater ingress getting behind the unit. However, the structural fixings securing the canopy to the wall may still be exposed and vulnerable to moisture.

So, unless the canopy has third-party product approval to use only a silicone sealant we would always recommend a lead cover flashing – again, it doesn’t need to be linked to a cavity tray so long as there’s one over the external door head.

Site-formed & prefabricated canopies over habitable accommodation

Where either of these canopies is provided over habitable accommodation; for example, a walk-in bay window or enclosed porches or conservatory, a flashing must be provided that is linked to a cavity tray.

For further information go to Chapter 7.9 - 7.12 of the LABC Warranty Technical Manual, which offers guidance weathering details to roof abutments. This easy to understand table explains when flashings and cavity trays are required.

Further information

Also read our Technical Guide: Viewpoint - Is a detached canopy a building?