Garage flat roof to pitched - cavity trays

3 Sep 2008
Reaction score
Tyne and Wear
United Kingdom
Hi, i have a flat roof garage linking between my house and the neighbouring house, i want to convert the garage to a room and replace the flat roof with a pitched. The building inspector has said about cavity trays where the new pitched roof will meet the existing external walls, does this mean on the neighbours external wall too? How does that work? can the builder just flash up the side of the wall and not penetrate the neighbours wall at all?

thanks for any help that might come my way...
Sponsored Links
Unless you want to be responsible for damp in their house.

You may have no right to do this work though, unless the neighbour agrees - with or without cavity trays.
Cavity trays are OK when done for new-build, but can be a pig to get right in existing walls. If the pointing is in good condition, there shouldn't be a problem.
Agree with Tone. Retro fitting CT's should always be looked at and decided upon individually and not an automatic 'fit them' from the architect.
Sponsored Links
But they are as important as any other dpc. And in this case the bco has asked for them anyway.

But fitting cavity trays into someone elses wall is another story.
If it's a party wall, the act allows for insertion of a DPC, but i wonder if there is any guidance on whether a cavity tray falls under DPC.
It wouldn't be trays I'd be inserting if someone wanted to make a living room next to my house ;) As it happens it's been done up the road though there are 2 garages joined. One for each house.
And in this case the bco has asked for them anyway.
Since when has a request from BC ever cut any sway with you or Tony?
I thought your mantra was to rebel Woods and offer alternative suggestions to such an intrusive and often botched method of repelling water ingress.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links