cavity tray

[Neil]

I have just been told by the building inspector that because the outside wall of my sons single storey extension will become an inside wall, we need to fit cavity trays above the tiles at lead flashing level. He suggests cutting out the mortar joints for 4 bricks at lead flashing level and putting a 9 inch DPC through to the inside blockwork, curling it up to make a tray. On the slope he suggests staggering this. I understand the theory of what he is saying but would appreciate any ideas on how to go about it. How would you join the short length of DPC to make it on continuous piece? We have not finished rafters yet so probably best to do the cavity trays first? Thanks for any input. Neil

[O.B.]

When I built such an extension nothing like this was suggested. Mind you that was 15yrs ago. However, there hasn't been a problem at all. More recently I had cavity insulation installed.

[Pete C]

Hi,

Maybe try feeding it in in one length as you go, doing 2 brick lengths of cutting and filling at a time. If making a wider slot it will be easier to cement it afterwards.

Wonder if it's possible to fold the DPC over at an angle so it can be fed in more easily.

Failing that if doing short runs it should be possible to turn the end of the DPC up a bit at the end of each run, by drilling through mortar between bricks and breaking out to the slot below.

Try searching asking on a UK self build forum, must have been done before.

cheers, Pete.

[Neil]