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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.

979 Damp Proofing questions

Damp kitchen floor - dug up concrete and earth below is damp - what are the next steps?

Hi have dug up the concrete in my small kitchen and I don't know what to do next. The earth below is damp and I doubt if there is any DPM underneath (house is 1900's) Any suggestions welcome!

If I lay the DPM Membrane, does it have to come up the walls all the way to accommodate all the layers? Sand, Kingspan and concrete etc?

Damp on wall next to conservatory (single skinned wall with no cavity)

I have a lean-to conservatory butting up to two walls. The one wall is very damp, it is a outhouse/coalhouse, which I presume is just a single skinned wall with no cavity. We have tried to fix it with silicone and plaster but the water still seems to be coming in. It seems like it is coming in through the gap at the top where it butts up against the roof of the coalhouse. Please could someone advise the correct solution.
Many thanks

Salt / white crystals under floor board in grade 2 listed mid terrace house

I live in a grade 2 listed mid terrace house, converted into 2 flats, and I live on the ground floor.
Last year some of my bedroom furniture developed mould spores, only on the backing panel and underside of drawers. As I thought there was a problem in the chimney, as furniture was in alcoves either side of it, I had a survey done. There was no damp in the chimney and I have no signs of damp in the walls or anywhere else. A dropped joist was identified and has been repaired and the underground ventilation cleared as this had become blocked with stones etc, and I now use a dehumidifier in this room for 12-14 hours a day as the humidity was high. The room now has a better atmosphere and feels warmer. A year later and on looking under a floor board I have seen what I believe is salt crystals, it looks like white crystals. Is this from any damp drying out and what should I do next please? Do I need a specialist or do I need to wait longer? I live in the Wiltshire area and am finding it difficult to find anyone who deals with damp in older houses.

Thank you for your response Joseph/plasterworks

Damp problems on party wall

I have some damp patches on my party wall. My neighbour has problems all around the ground floor. They had a dpc injected 18 years ago but did not renew the plaster. On the party wall from their side there is no evidence of holes where a dpc was supposed to have been injected. Should you be able to see evidence that it was actually done? We think it may not have been & the damp patches in my house are coming through from their side. Does this seem likely?

Condensation and mould around the windows

I have noticed that I am getting quite a lot of condensation around the upper floor north facing windows in my house. This has resulted in mould around the windows, the widow panes and the grooves in the windows. I am also getting mould on the internal walls in one room which is above the window and on the ceiling. In another room the wall has an orange stain and feels wet to touch. Can anyone help me on whether this can be rectified by me or whether I will need a tradesman to come out and take a look.


Paint bubbling up and black spot marks in front room

Hi I live in mid terraced house, not sure how old sorry, but the outside front is stone with brick around the window bays and door.

Don't now much about the house moved in about a yr ago.

The possible damp is in my front living room, just where the wall under the bay windows is.

What I can see is the paint bubbling up and black spot marks.

I have had two people to have a look and both said completely different things, the first said he will have to take it back to the brick then re do it all as there was no condensation and he says it looks like it has had a damp course of the drill holes in the wall. Also he said something about the air vents I already have outside so that ruled something else out.

The second said it is because the house is over a 100 years old and the cavities have failed and advised me to replaster or just to re decorate every year.

Also I would like to add the whole ground floor is concrete sub floor except this room which is timber. Can anyone explain why this may be?

Thanks in advance to any advice :)

Damp proofing a rubble wall

I have a west-facing wall about 500mm thick in total. The outer is of rubble type construction built from random rocks (I took the external render off to renew and stop rain driving through). However this did not resolve the problem so the damp is obviously rising. There may well be an inner block skin, and no cavity that I am aware of. Is it possible to chemically inject such a thick and random wall?

damp wall on old rubble walled cottage

I live in a c. 250 year old detached cottage. The walls are solid stone / rubble c. 1’ thick.
We are experiencing what I believe is rising damp on the inside of what is an external facing wall. It is only on 1 wall (the adjacent wall, that is also external facing, has no signs of damp whatsoever and has been tested with meter - it was bone dry). The damp patch is in a wave running the width of the wall (about 12’) and height of 4’ at its peak, running to c. 1’ at the corner.
The periods of damp are highly intermittent – we have periods where the wall is very dry, and periods where it is wet to the touch. As a general trend it is worse in the evenings than at any other time during day.
We have a “copper wire” DPC installed (this was present when we purchased the house). The green light is on at the base of the unit and there are no other signs of damp on any other wall so can only assume this circuit is still complete and the dpc is working.
We had a surveyor friend round who believes issue is rising damp. The wall we were experiencing the problem had a concrete path running along the outside that was quite a bit higher than the internal floor. He suggested the dpc may be being breached by this path so suggested we dig this up so external floor is same level as internal, which we have done. The damp dried up for a week or so, but has now crept back. This could have been entirely coincidental – as per above, the periods of damp are highly intermittent.
There is a set of pipes running from the boiler into the house at the wall that we are experiencing the damp. It has been suggested a small crack in these pipes could be source of damp, but we were advised the dpc should stop this anyway…
Please help – any advice greatly appreciated!! Not really sure where to go next, but trying to avoid spending too much money as long term plan is to extend the house an ultimately knock down the offending wall anyway!
Many thanks

Damp in hallway of 1880s sandstone house

For a while now, my hallway has become very wet whenever it rains. This affects both sides of the doorway and the damp can go approx half a meter high. A builder says it was caused by a prolonged period of heavy rain last year (apparently the same has happened with other houses in the area). He gave it damp proof injections (cream) but this has failed.

My concern is that the house is an 1880's sandstone house and I have since discovered through internet research that old houses should not have damp proof courses or use waterproof plaster as this can exacerbate the issue. I'm yet to discover what the cure is though!

Any help would be much appreciated as I don't want to keep throwing money away or make the issue worse.

Solution Required for Penetrating Damp


I rent out a 1930's 3 bedroom semi in BD19 postcode and I'm looking for a solution for a damp problem probably caused by poor ventilation. Please see below:

Mold patches / spores around the main bedroom window where the ceiling meets the wall. Also in a cupboard where an old storage tank used to be located (mold spores on the ceiling) with a permanent foisty smell generally throughout the room.

Wet wall underneath the window, condensation is the expected cause, but another reason may exist as it gets very wet.

I will be looking at installing some trickle vents to reduce / eliminate the condensation, however I suspect that the penetrating damp is being caused by either poor pointing and or problems with the fascia, soffit and / or gutter.

If anyone can provide a solution it would be appreciated!

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