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Damp Proofing Questions

Our expert damp proofers have kindly agreed to share their wisdom on such topics as removing mould patches, rotten timber, causes of mildew, damp basements, rising damp, floor construction, flooding and waterproofing and much more.

1,054 Damp Proofing questions

damp dots showing through plasterboard studs

I live in a conversion done in the early 70s. On many of the walls inside there are damp dots spaced fairly evenly in vertical lines where the studs are. Presumably the dots are where the screws fix the plasterboard to the studs.

Is this simply condensation, or does it indicate inferior construction?

Thanks to all who have replied. I am thinking of cutting out a piece of plasterboard to get more information about the construction inside the wall before working out what to do.

Do I need to have a sump pump installed in my cellar if I am having it water-proofed?

cellar has black rot due to poor ventilation and is under ground level, but has never flooded before. I have had several damp-proof companies come to have a look, and some say it must have sump pump due to BS regulations or something, and others say, no the floor is dry so doesnt need one, just needs p20 membrane tanking system and humidistat fan.Please advise me, it's alot of money to gamble and I dont know who to believe.
thanks a million

An alternative to removing existing render?


We have damp along our Kitchen wall which according to the Damp expert who visited, is due to condensation (salt in the walls) rather than Rising damp.

He recommended to "hack off & renew" and line the wall with Thermo boards.

I'm reluctant to go down the "hacking off" route because of the disruption! and wondered would it be possible to simply cover the existing wall with the Thermo boards mentioned etc or something similar?


wet floor and wall under kitchen units

Not long moved into house. Had problem with slugs in kitchen and after removing plinths/ kick plates under units found the the floor to be wet and black mould on walls. Can't locate a leak. Slabs on patio were right against house wall and were sloping towards house. I've moved these. Any assistance appreciated. What sort of local professional should I be approaching?

Mould on external walls of first floor flat

"I am moving into a new flat (for me) but built in around 1985. It is a first floor flat but on the walls in bedroom 1 and 2 is mould at floor level. It only appears on the external walls. Does this mean bad ventilation and is there an easy way of getting rid of it successfully. Is it treatable without putting air bricks through external wall which I dont think the Management Company would be too keen about."

Will Patio Cause Damp

Hi, I have a question regarding patios splashing rain water onto external walls.

Is there really a difference between rain that has fallen directly into external walls and rain that has bounced off a patio and into external walls?

Seems like it's the same rain and the walls will dry out just as quickly.

Here's my concern...

I have a patio in my back garden which is too high with regard to the internal floor level, there is only about a 40mm drop. I can't see the DPC but it's probably to close to that as well.

There is a gap of about 6 inches between the house and the patio filled with corse gravel.

I've got myself worried about rain splashing off the patio and onto the house causing internal damp problems.

There is no internal damp at the moment but worried it might appear in the future (it's a freshly renovated house that we moved into in feb).

There are a million different opinions on the Internet but the one thing everyone appears to agree on is that splashback causes damp.

Should I take action and lower the patio or am I just worrying for no reason.

Please can somebody put my mind at ease, I've become very confused by it.

Thanks in advance

Internal wall Damp patches during heavy rain fall dries out in dry weather

Hi we have an internal wall single brick, recently had it damp proofed and concrete plastered to 1 Mtr high we are now getting damp patches at 1.5 mtrs in times of rain which dry out again with dry weather. Can anyone help pls?

Rendered property left unsightly after damp course, what do I do next?

Really need some advice please. We had a damp proof course installed on a property that was fully rendered. The contractors cut a channel out of the render and installed the damp course but some of the render came off in the process and now it just looks a total mess with this deep channel and broken render. I'm not sure whether this is normal practice and I don't know whether the channel needs re rendering or painting or sealing somehow and I'm not sure what to do next. Can anyone advise please?

Damp and Timber report cost

Dear all,

I'm in the process of buying a 2-bed mid-terrace house in London. The home buyer report showed high levels of damp in certain parts of the house. The surveyor recommended -before exchange- to "Obtain a Damp and Timber report. The report should include a check for any possible infestation of ground floor timbers. Obtain all costs for necessary treatment from a PCA affiliated Damp Treatment contractor. All timbers should be checked for wood boring infestation and other decay simultaneously"

How much can I expect to pay for such report?

Thank you very much!

Damp from 'defective roof coverings'

Hi there,
I am currently in the process of buying a two bed victorian terrace house and the Estate Agents have recently had a damp survey carried out on the property (3 weeks ago)
The company have quoted for DPC treatments in the stairwell areas and the kitchen and have also stated that:
'Areas of damp were noted at high level in the rear bedroom and landing. This damp is due to defective roof coverings'
This is the damp coming in from the ceiling of the rear bedroom that was evident when I viewed the property and I suspect is where the chimney is.
I had first thought that getting this sorted was included in the quote that the Estate Agents had passed on but now realise this will extra cost..
My first question is how do I go about getting a quote for this will I need to get a roofing specialist? Then do I need another person to sort the damp?
I know it is almost impossible but looking for a ballpark rough idea of how much this is going to cost, I realise this will involve either scaffolding and a scaffold tower. Any information gratefully received!
Many thanks

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