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Root cause of damp (i do not prefer the damp injections)

In process to buy a property. Its a 3 bed 1950s semi with double walls (can't remember the correct term). It has DPC installed, but is within 75mm from the ground. It also has some sort of gutter (full it stones/pebbles) all along the walls.

Question: The wall with patio doors to the lounge has some damp. This damp is near some sort of ventilation (i can see it both from inside and outside).

I had a home buyers survey done, and as expected they pointed out the damp in the corner. They also mentioned it may be due to failed DPC.

Estate agent arranged for a Damp consultant to get me a quote. The quote mentioned need to remove the plaster for 1m on the wall and inject some chemical and do a special replaster.

I am against the whole injection thing. I need someone who is skilled to identify the cause. It might well be that the water is coming in from the ventilation? or there is something attached to the wall that is causing it. (between there are a few nails, wires and a timber frame-for some sort of tree to climb over it) on the outside wall.

Can you please help?

3 Answers from MyBuilder Architectural Designers

Best Answer

without actually looking at the problem it is impossible to be 100% sure of the cause, injected damp proofing is really only successful if it is rising damp.
rising damp is misdiagnosed in over 75% of cases.
sounds like an old fashioned French drain has been installed around the property as the outside ground level is to high.
depends really where about in the country you are if your local to Lincolnshire would be happy to have a look and advise.

good luck Alex


Answered 11th Sep 2015

Correct term is 'cavity', two walls with an air gap in between, maybe 50mm.

Yes, it could be failed dpc. Yes it could be other cause. What you seek is a 'true positive' diagnosis, which means the correct symptom AND correct cause.

One inspection method is use of an endoscopic camera. Most local Surveyors will have one of these. Basically, it may be prudent to make a hole in the wall and have a look in, with the camera. You may then possibly identify the cause, ie, a defective dpc, or some debris bridging the cavity for instance. Is rain water ingressing around the vent somehow, and sitting on the existing dpc, who knows?

Lastly, given your anti damp proof injection position, you may want to peruse Howell's 'The Rising Damp Myth'!


Answered 11th Sep 2015

It looks like you've had a damp specialist already,
The vent should actually aid drying out of wet plaster
Looks like it's been identified as rising damp so that's the root cause
The solution is next, some drill and inject, whereas we are one step ahead of the dpc game we use tanking membrane as our preferred methodology
If the existing plaster is wet then it will be contaminated with salts such as nitrates sulphites and possibly chlorides, therefore these salts are hygroscopic they attract moisture form the air so even if a drill and injection method is employed the plaster needs to be changed.
It doesn't state why your against the injection method????
Any further information just ring me Signature Design, Build and Restoration Ltd


Answered 11th Sep 2015

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