Our house walls have a cavity formed by two leafs of lightweight block with an external facing of rough cut stone. A new extension with a flat roof is to be built out from such a wall. This requires a cavity tray to be inserted along the roof line but all the ready-made trays I see are designed for a single brick width plus typical cavity width. Our outer leaf is more like two brick widths - what would normally be done in this situation?
Cavity tray for extra wide wall
- Thread starter vexation
- Start date
-
- Tags
- cavity tray
I suppose it might work if it reached in far enough, at least to half way across the cavity to catch drips off of ties above. But then it would also need to slope down to the outside to drain out of a set of weep holes. A lead flashing is going in underneath so I guess this could be done with one wider strip of lead instead.
The outer wall is sandstone with big mortar joints and faces N.E. so it can get a good hammering with rain. I've seen a few damp patches in the attic on this end gable where dirty ties have bridged water over in exceptionally foul weather so I'm not prepared to take chances on this one.
Stick some dpc along with the cavity tray, so your tray only covers the first outerskin then the dpc would sit under this and over the outer skin.