I've been told I need to do this due to damp in an area of the house
at the rear which has a concrete floor.
The external area currently has paving slabs. I could take all of
these up and re-lay them having removed 6" of soil but as the whole
paved area is about 25M sq this would be quite a lot of work and
require serveral skips to remove the soil.
I'm thinking about lifting the slab nearest the wall, remove the soil
close to the wall and replace with bricks (but leaving a gap of 1" or
2" between the bricks and the wall for ventilation purposes), then
replace the slab.
Will this work and has anybody done anything similar?
You don't say where your paving level is in relation to the dpc, but I assume
they are about level. In new build situations the Building Regs require the
ground level to be 6" below dpc - the reasoning for this is that rainwater can
splash up that far, especially from a hard paved surface. So if you plan on
keeping the paving slabs at the existing level and having only a 1" gap between
them and the wall this won't help at all.
The normal way of getting over this is to form a channel or trench against the
house wall, at least 6" wide although 8" or more would be better. The bottom of
the channel must be at least 6" below dpc level. A bed of gravel or shingle can
then be laid in the channel up to say minimum 2" below dpc. This allows
rainwater to drain away below dpc level and does not cause the splashing
Should work fine, particularly if you have gravel soil. If you have clay,
you might find it just acts like a pond and you need to supply proper
drainage to prevent puddling. This is frequently not difficult to supply, as
a gutter downpipe is likely to run nearby which might be suitable.
firstname.lastname@example.org (DIY Novice) wrote in
My house's back wall is separated from my garden by such a gap. The wall
is a bit damp, because over time dust, leaves etc have washed/fallen into
the gap (about 4 feet deep, but less than 1" wide!).
A gap only 6" deep & 2" wide would be easier to keep clear, but you may
want to make it a bit wider so you can get a trowel into it.
I had pretty much the same situation. Actually I still do, but
the damp has gone without doing anything to the outside at all.
I did two things, and I'm not sure which cured the problem.
Firstly, I installed central heating. Previously the heating
in the house was uneven and it was the colder areas which got
damp, so it could have been condensation in part.
Secondly, I replastered the damp areas using a
sand/cement/lime/waterproofer scratch (base) coat, and the damp
will not penetrate that even if the wall itself is still slightly
The other thing is to keep a careful eye on the external pointing
where the water splashes up the outside wall. It will likely need
more frequent attention than the rest of the pointing, and if it
is allowed to deteriorate for long, the bricks could become
damaged. However, seek advice here or elsewhere before slapping
just any old mortar mix in, as the wrong mix could damage the
bricks even faster.
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