Damp Proof Question

5 Feb 2016
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United Kingdom
I'm working on damp-proofing my garage. The problem is that the previous owner laid a concrete path outside the garage wall which is 8cm higher than the damp-proof-course. This is causing damp to come in from the concrete and the DPC I have is too low down to stop it.

I am wondering if this solution will work: put a new DPC above the level of the concrete slab to stop any damp rising up, and to paint on a flexible, rubberised bitumen layer (like http://www.toolstation.com/shop/p33714) below this to stop any damp coming through.

Hopefully these few photos will show what I mean - what is there at the moment and what I am thinking of doing.



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There will be moisture getting through the walls above, so it's no use just dealing with the damp you can see near to the floor. Does the floor have a DPM too?

If you are damp proofing for a reason, ie making an internal room, then you need to deal with the walls and floor as a whole, not just a bit near to the floor. Otherwise, just increasing ventilation with deal with air moisture.

Yes surface coatings with work for a few years until the damp pushes it off, or it cracks. The mortar joints need to be solid and hard, else lose grains detach along with the coating.

A strong render 900mm up the wall could do a better longer lasting job. Or chemical injection.
I'm planning to convert the garage into a utility room / office, so battening, insulating and plasterboarding the walls, and putting in a laminate floor. Not sure if there is a DPM on the concrete floor - no damp comes through - and I was looking at laminate underlay with in-built DPM.
In that case, lining the wall and floor with a DPM will keep the room dry, without you needing to mess about with the wall.
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Could you expand a bit more on exactly what you mean? (I'm at the novice end of DIY!). Are you saying I won't need to put in a Dryrod style damp-proof-course, just fix a damp-proof-membrane to cover the whole wall? Just fix that to the battens? I was looking at using Thermawrap insulation (http://bit.ly/1TgVusS) which is water resistant - would that still need a damp proof membrane on first?
A polyphene DPM up the wall, and taped to the same over the floor.
Then fix your wall battens and floor joists.
Insualte between them
Vapour-check barrier or foil-backed plasterboard to the walls
Normal floor boarding to the floor
Word of caution the DPC laid on the floor needs to be carefully looked at when you lay your new joists else it might get pierced by sharp bits of the original floor, so check for these first.


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