Fitting a Cavity Wall Drip Tray - Does This Need to be done?

[collectors]

Hi, just at the early stages of an extension & was wondering if fitting a cavity wall drip tray had to be done above all openings like windows & doors & around the whole base of the extension.
Cant seem to find good info on this.
I was also wondering how you fit the cavity wall insulation to the tray.

Thanks.

[welsh brickie]

if you use catnic boot lintols above all the openings then you don't need cavity trays as they are designed to work in the same fashion.
As for the the need of it around the base, if its a concrete floor, you build the inner leaf to floor height,concrete the floor and leave the outer course lower, the dpm is then left to drape over the inner leaf to form a damp tray to the outer leaf

[collectors]

Thanks for getting back. Do you mean a bit like this image & add the small weep/drip outlets every now & then in the vertical course's ??

[welsh brickie]

yes that's right but the dpm needs to be lower by another course on the outer skin to allow for mortar droppings and the dpm is level with the inner course

[collectors]

Thanks for the info. I found the drawing on the web & changed to show the DPM, but i noticed the order of materials from the groud up was:
Hardcore
Blinding slab
Insulation
1200 DPM sheet
Floor screed

But on my pans the order is:

Hard core
35mm min blinding
1200 DPM sheet
Insulation
Floor screed

One has the DPM under the insulation & 1 over the top. Have you had experiance with this or should i check with the local DS.

Cheers

[welsh brickie]

local council officers differ from each county, you need to check before commencement, they will need to check foundation depth before the concrete pour, once up to dpc height and the sub base laid and compacted they will tell you what they require.

[collectors]

Nice one, thanks for the help.