Cavity tray for opening into new extension

[cox377]

Hello guys,

I'm currently building a small lean to extension on the rear of my house.

The lead flashing of the lean to roof goes right upto and under a large Victorian window.

1 meter down from that window is the opening through the cavity through to the new extension.

I'm starting to wonder if this would require a cavity tray as any external wall above the new opening is now in the roof void and directly above that is the window.

If a cavity tray is required, what sort of tray would be best?

Much appreciated

James

 

[freddiemercurystwin]

BC nearly always insist on them (and rightly so IMO) Cavity Trays do a retrofit one. You have to do them one at a time, they're a monster PITA to fit (apparently). http://www.cavitytrays.co.uk/pdf/23-Type-E.pdf

 

[cox377]

The trouble being, if this tray was above the lintel then it would seep out of the wall above the lintel, which is inside the extension.

Ideally, I need a cavity tray that angles left and right so any drops fall into the cavity left and right of the doorway.

 

[freddiemercurystwin]

No this goes in where the new extension roof abuts the existing wall.

 

[noseall]

The tray should be located so that when water is discharged out of the cavity, it does so just above the lead flashing line at the roof abutment (as per Freddy).

If the abutment happens to be a pitched affair as opposed to a straight lean-to, then good luck to ya.

Absolute fekkin nightmare. You have to have the foresight or prediction of the roof pitch, rafter location and thickness of roof material and work from there, as well as messing up and weakening the brickwork.

Retro-fitting of cavity trays ought to be a practical test for all those pen pushers who specify them.

 

[freddiemercurystwin]

We'll specify 'em you slot 'em in!

 

[noseall]

We'll specify 'em you slot 'em in!

Seriously Fred, you try and work one out one day and actually try and install them. You will wish you had never been born.

 

[freddiemercurystwin]

Nah, could do it with me eyes close, one hand tied behind me back, hanging upside down. Absolute doddle!

 

[noseall]

Did you know that with full fill dri-therm insulation, the manufacturers of the insulation say their product will not admit water and require no additional cavity protection?

Weep vents at lintels is all that is required.

 

[cox377]

I'm getting what your saying. Sounds like a bloody nightmare to me. It's a lean to roof and not a pitched one. BC haven't mentioned anything so I'm not quite sure what he will say. I'm looking around my area at all the lean to extensions and thinking I'll be damned if they've got bloody cavity trays installed.

I will play this one by ear I think and see what happens.

J