Not another damp problem

[Fizzer]

Hi All, sorry for posting yet another damp problem, I've been reading this forum for some time as we (my wife and I) are buying an old detached cottage which has some rising damp and penetrating damp.

The details are:
the house has been poorly ventilated/heated over winter as it's been vacant
we intend to install gas central heating
the floors at the front of the house at least have a screed + bitumin like layer + chipboard (rotten near the walls)
The back of the house has a tiled floor (kitchen) and rear wall (bathroom)
The west wall of the house has a sloping driveway touching it (ground level at the front 4' deep at the back) the inside face of this wall appears to have been tanked.
The back wall also 4' underground and is approx 1' 6" thick (the garden slopes up from the back wall)

The problem is:
All of the old downstairs walls (including internal) have patches of popped plaster and rising damp
the floor at the front west corner of the house is v v damp (+mould all ov er the wall here)
under the kitchen cabinets against the back wall it's v damp.

My theory is:
the concrete floor has reduced moisture dissipation and is forcing water up the walls
the tanked west wall is forcing water into the adjacent south wall and floor (tanking not linked to bitumin layer??)
the earth at the back wall is forcing too much moisture into the back wall
a 4-5' deep french drain at the back of the house is too deep and may undermine shallow footings

We've had the obligatory free damp surveys and, you guessed it, got the 'inject chemicals everywhere, tank the back wall, install a dpm on the floor of the south west room' quotes.

My questions are:
After reading lots of info here, tanking and chemical dpc's aren't ideal, but if we don't do that, and it doesn't dry out on its own, what do we do?

Is it feasable to dig down and install a vertical dpm against the back wall to stop water coming in, or will this lead to a dangerous buildup of moisture underground?

TIA

Andy

 

[Fizzer]

Here's a great article I just found:
http://www.oldhouse.info/ohdamp.htm

 

[Matt Green]

The problem is:
All of the old downstairs walls (including internal) have patches of popped plaster and rising damp

What are the skirting boards like?

the floor at the front west corner of the house is v v damp (+mould all ov er the wall here)

That's likely to be condensation. Mould doesn't like ground water: too salty.

under the kitchen cabinets against the back wall it's v damp.

how so?

My theory is:
the concrete floor has reduced moisture dissipation and is forcing water up the walls
the tanked west wall is forcing water into the adjacent south wall and floor (tanking not linked to bitumin layer??)
the earth at the back wall is forcing too much moisture into the back wall
a 4-5' deep french drain at the back of the house is too deep and may undermine shallow footings

All sounds reasonable to me.

Chemical DPC isn't going to help the lateral penetration. A vertical barrier would be good, but a lot work moving earth. Removing the plaster and lining the walls seems a pretty reasonable plan as long as there's not a vast amount of water coming through it.

The internal walls are a problem though. The concrete floors are pushing ground water up them. remove the skirtings and check the plaster doesn't run into contact with the floor. Hacking off as big a channnel of plaster as can be hidden behing the skirting might also limit the damage by maximising the amount of water capable of evaporating through the wall/floor junction.


Matt

 

[Fizzer]

The skirting boards don't seem bad except in the front west corner. not sure if there is a skirt behind the kitchen units

Under the kitchen units the chipboard floor covering is mush this is over the entire area under the cupboards so my guess is that it extends under the tiles in the kitchen.

Ok, next question about lining the outside of the wall:

If I can find the labour to dig down to floor level, line the wall externally and replace the earth with a gravel top, is it likely to cause more water to be forced down into the floor? i.e. will I just move the problem somewhere else?

what can I do about the cocrete floors? digging them up seems a bit drastic!

 

[Moo]

Under the kitchen units the chipboard floor covering is mush this is over the entire area under the cupboards

Have you checked the plumbing?
We discovered exactly the same when our son moved into his house and tracked the cause down to a very slow leak.