Cavity tray above extension

[Dannyj1984]

We have a side extension with a utility room in and the roof has started leaking a little. We are looking to repair the roof but before doing this, the inside is currently boarded out with some wood. We want to plasterboard this to make it look better. But wondered if there should be some kind of damp protection above the roof?

My thinking is if the external wall gets wet then the water soaks down the brick and will affect the plasterboard inside?

Would removing a course of brick and inserting cavity trays be recommended?

We are replacing the plywood under the roof which is damp (the leaks have been caused by the perished rubber seals on the screws that hold the metal roof on. So whilst this is off it would be much easier to access above the roof to put in the cavity try and the flashing.

So in short my question is should we install these cavity trays to prevent water soaking down the brick and affecting the internal wall in the extension

Thanks

 

[Notch7]

Im not sure what you are trying to achieve exactly.

But in general, a cavity tray is fitted by removing 2 rows of bricks on the external skin of the wall and the tray fitted. Its quite awkward to do.

what the cavity tray does is stop water that might get inside the wall cavity and running down until it hits an obstruction or just making the wall damp.
the tray has a lip that extends out to the external face of the brickwork that acts as a damp proof course -and the tray allows water to weep out.
Generally the external roof flashing goes directly underneath the cavity tray lip on the same slot.

If this is not a properly built extension I doubt whether the sides where they join have vertical DPCs fitted.

if you want to plaster the original brick house wall, I would suggest, battening out the wall with 50 x 25 treated tile battens, then fit foil backed plasterboard. Stop the plasterboard short of the ground by an inch or so, cover with skirting. that is a reasonable alternative to cavity trays, but not guaranteed to prevent damp -you can only judge by whether the wall gets damp now.

 

[Dannyj1984]

Im not sure what you are trying to achieve exactly.

But in general, a cavity tray is fitted by removing 2 rows of bricks on the external skin of the wall and the tray fitted. Its quite awkward to do.

what the cavity tray does is stop water that might get inside the wall cavity and running down until it hits an obstruction or just making the wall damp.
the tray has a lip that extends out to the external face of the brickwork that acts as a damp proof course -and the tray allows water to weep out.
Generally the external roof flashing goes directly underneath the cavity tray lip on the same slot.

If this is not a properly built extension I doubt whether the sides where they join have vertical DPCs fitted.

if you want to plaster the original brick house wall, I would suggest, battening out the wall with 50 x 25 treated tile battens, then fit foil backed plasterboard. Stop the plasterboard short of the ground by an inch or so, cover with skirting. that is a reasonable alternative to cavity trays, but not guaranteed to prevent damp -you can only judge by whether the wall gets damp now.

Thanks notch. Fortunately my dad's a bricklayer albeit retired. But has 50+ years experience. He's the one who mentioned the cavity tray but he does like to go ott on every job. It's going to be tricky to get to which is why if it needs doing it makes sense the take the current roof off and access it that way.

If there is an alternative that would be much preferred. As the current wall is boarded out with some type of wood. I don't know at the moment how wet the wall gets. I'm tempted to take some of the wood off and see what it's like over the next week. We've had a lot of rain and it's forecast to rain most of next week. So I could see if the wall gets wet.

Danny