Part of my build is 100mm concrete block innerleaf / 200mm cavity full fill with isover CWS bats / 100mm concrete block outer with an additional "cladding" of 100mm cut natural stonework which is built with lime mortar. This stops at lintel height and will be capped with slate or aluminium and the wall then continues as 100mm block outer leaf which will be rendered.
Question i have is do i need to put a membrane between the stonework and outer concrete block? I know the stonework and lime mortar will let moisture wick, but i wondered how wet the outer conc block will get during driving rain. We are on a very exposed site weatherwise. I considered putting some dpm lapped at the joints..mate reckons this will cause problems if water gets behind it and cant get out. Any opinions welcome....
Thanks

I definitely would not do a dpm. There are proprietary products available that introduce a drainage layer.

I would not bother, the lime will sort it all but ensure that there is a good drip to the render above it all.

Tony. Thanks. I think the lime will be ok but just wanted a second opinion.
Mike. Thanks, the DPM is the outer pary of a cavity tray sitting on an EPS wedge.
Pic of wall showing build up before cavity tray put on.
Edit..dont know why pics rotate 90deg when i post them up?

Gave myself whiplash viewing your post. My lawyers will be in touch...

No point in a vertical membrane. Will you wall tie the stone to the block? Without this it may de-laminate. Would bonded EPS platinum beads be better for the fill?

Posted By: Mike GeorgeI would leave the DPM where it is. I see no reason to cut it out and only risk of water penetrating into the concrete blocks if you do. Don't forget most stone will not absorb water and when it rains the inboard face is likely to get saturated via water penetrating through beds and perps. I would use perpend vents in the bottom course at regular intervals to allow any water to discharge

I didn't see the fine detail of construction but I think that sounds like what was done for some nearby "recently built to modern standards but look like old" thatched cottages that are essentially a timber kit & insulation, then blockwork outer skin, then a thick (essentially) cosmetic layer of stone. There are 'weeps' around the base of the stonework.

If you go to the bottom of
http://isleofskyecottages.com/gallery/
then click the "Building" link, some of the images show the walls during addition of the stonework.

Posted By: Nick ParsonsSilly point, maybe, but could you rotate the pic 90 degrees out in your 'Pictures' file before you post it to GBF? That way we either get it correct, or upside-down, depending on whether they are left-hand or right-hand degrees!

Tried that but the pic keeps ending up the same way when i post it.