Cavity Tray Installation

[gjames]

As part of a garage conversion project I'm working on, I need to install cavity trays above the garage roof. I was ready to install the trays I have bought which are the 450mm wide type which interlink.

I drilled out the first brick to inspect and to install the tray, but in doing do discovered there is already a thick plastic membrane running into the mortar and runs across both bricks either side.

I haven't taken any other bricks out as yet, I wanted to see in anyone has any thoughts as to whether this is already some form of cavity tray that has been installed?
There are no weep holes, so I assume the way to proceed is to drill along and if it runs all the way across, just install weep holes?
It's a 1980s timber frame house.

 

[Dad'n'lad]

If you put your hand in and feel if it comes down from the inner skin, you're ok. You'd need to drill out the perps nearest to its ends. The problem would be, that that is where it would fold to create its end stop.

 

[gjames]

If you put your hand in and feel if it comes down from the inner skin, you're ok. You'd need to drill out the perps nearest to its ends. The problem would be, that that is where it would fold to create its end stop.

Thanks for the reply, I think it's coming from the inner skin, but hard to say for sure, may have to try again tomorrow. It's timber frame so inner skin is ply with housewrap, I assume if it's attached, it's probably nailed to the ply.

As you suggest, will need to drill some perps to walk out where it's running and where it folds up. At the same time I'm keen not to destroy too much of the brick and plastic.

Also it runs along a sloping flat roof, so there is a chance it may step down.

The strange thing is that there are no weep holes. Would it have been standard at the time of construction to put in a cavity tray but not weep holes?

 

[Dad'n'lad]

sorrygjames, have not got a clue regarding timber frame.