Good evening.
I have been asked to quote a job where a client requires a new patio to be built up against a garage wall. The garage is built into a sloping garden and the client would like me to level the garden right up to the very top of the existing slope.
The garage wall is a single skin wall with 1 small pillar on the inside of the garage and therefore does not have the strength required to retain the new levels required.
Decking was fixed to the garage wall previously and the existing soil levels are 150mm below dpc so damp was never an issue.
What i had intended to do was build a new block wall tight to the garage wall for the required strength to retain. (finished level of new patio will be 10 courses above dpc) But i am confused on the correct way to protect from damp, can anybody shed some light. I have seen some specialist damp proofing online which effectively lines the garage wall but i am concerned about rainwater running down the garage and being trapped between the wall and the damp proofing. The only way i can see to avoid trapping any water is to add a lead flashingover the top of the "dpc liner".
Alternatively i could build the block wall with a cavity between and fill with clean pea gravel but would this be sufficient?
The rest of the work isnt a problem, installing land drain pipe and soak away etc, its just the damp issue on the garage wall.
Sorry for the lack of knowledge here, we normally only install patios under dpc or with linear drains etc.
Any help on this will be greatly appreciated.
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Replies
cover the wall with visquean (polithine) stick it on with a sutable mastic and two good beads at the top, build a retaing wall out of hollow concreate blocks drive some metal rods through the hollows into the ground then fill with concrete, put a land drain pipe at the bottom then you are redy to backfill
also its not the don thing to flag right up to brick work these days 2 in of gravel round tuck 9in DPC nder the flag stick it as before then gravel on top
Thanks for quick response. Are you talking about the branded specialist stuff or just dpm sheeting? Are you suggesting i build the new wall tight to the visqueen?can you elaborate on this also "2 in of gravel round tuck 9in DPC nder the flag stick it as before then gravel on top"
I intend to leave a gravel edge as surface water will be heading towards the garage.
Thanks again
just the dpc sheeting build the wall tight to the garage wall tucking dpc under the flags next to the wall with gravel covering it but the flags should fall away from the garage
Ok i can change the fall no problem. Is there any possibility you could muster up a quick drawning of the cross section of what you mean. I cant work out if you are suggesting run the dpm down the garage wall or to stick it to the wall then fold it in front of block wall. If folding in front. Would the block wall not absorb water from surrounding ground and ultimately pass it on to garage wall?
You could always add a painted layer of SBR mixed in the ration for a bonding coat (SBR mixed with cement into a thick paintable slurry)
this stuff is fantastic and i use this for external rendering between coats which creates a waterproof barrier and it soaks into the brickwork and render etc (currently using it for a brick dog kennel im building for a friend to seal walls and floors)
you can also use this for sealing floors before screeds and many other aplications where a waterproof barrier is needed
Seeif this works Scott
CROSS SECTION.odg
Yes thanks for that. Makes sense. So i would need to dig right down and extend the footings of the garage and build up from that level, and then the dpm needs to run down the wall to at least 150mm below existing dpc?