Cavity tray installation

SVP · Post by **SVP** » Sat Oct 10, 2020 10:21 am

Do these look like they have been installed correctly? I thought they have to be linked to the lead flashing?

ayjay · Post by **ayjay** » Sat Oct 10, 2020 12:06 pm

I guess this is a new idea: I've never seen cavity trays fitted above a stepped flashing and by my reckoning there must be millions more of them around the country without cavity trays above them.

That doesn't answer your question, but I don't think it's anything to worry about.

Razor · Post by **Razor** » Sat Oct 10, 2020 1:20 pm

They don't have to be behind the flashing. This might clarify things

wes56 · Post by **wes56** » Thu Oct 15, 2020 12:45 am

Roger Bisby is a good plumber but he's now-a-days getting over his ski's ie he's often talking b....k's. His vid is confusing and wrong in parts.

Correctly done, first the flashing is turned (or built) into the bed(s) & then the Cav trays are installed to sit directly on top of the flashing.
The "weeps" should drip onto lead not on to brickwork.
On pitched roof new work abutments there are custom flashing/cav tray pieces that are built-in as the brickie goes up - a common practice for years.

Quite whats happening in the pics or how it was done i cant make out? My bad i'm sure.

fwiw: I've seen and done remedial repairs on lots of faulty or missing Cav Tray positions, usually over retro knock-thro's - missing cav trays in particular can cause extensive damp damage to decorations, plaster and occasionally woodwork.
Notwithstanding the sometimes perfectly dry locations of missing CT's - to my mind Cav Trays are an important building detail in pitched or flat roof abutments.