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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.

1,000 Damp Proofing questions

rising damp in a very old building Victorian house

hi i have bought detached house that converted to two flats about 2 years ago the building it self showing sign of rising dump i have drilled out side the walls all around the house, and inject the cream into the walls
my main problem is down stairs in the shower room were i have injected inside and out side the wall put completely new sand and cement into the walls after we strip it to brisks and yet still after 4 weeks i have patches in the wall that not dried and still dump what do i do i cant put tills and put back the shower until it completely dry and its not.
there is no pips only in the floor (when we strip the wall we did not see any pips on those particularly patches this is second time i had to take out tills and shower what do i need to do ) please help me

Large damp patch on 1st floor chimney breast

Last week a Large (1 Meter sq) damp patch appeared on the internal chimney breast on the first floor. The patch was wet to the touch and there are patches where the chimney breast protrudes front the wall in the upper comers. The damp patch has not dried out but is not getting any larger. I am not sure how it has appeared or what the solution will be. The wall will need redecorating, but I need to identify the route cause first. Does anyone have any experience of this type of damp?

Treating a damp wall after damp proofing external walls and inside walls replastered

A 3 bed semi-detached house had a ground floor bathroom that was not ventilated properly and had a broken sealant round the bath. The walls were damp and soaked. This was in January 2014. I had a specialist in, who recommended to damp proof the external walls. In the inside walls the plaster was removed and re-plastered.

Eight months down, the wall still feels damp and the bedroom upstairs the bath has the walls damp. I am not sure how this is getting damp or what to do to fix the problem. The exterior is pebble dash render.

Any suggestions or advise?


The property was built in 1935 so about 80 years. The survey report says block cavity render but looks more like just bricks with thick plaster.

How to cure damp spots

Just had a new roof, old plaster taken off and re-skimmed in bedrooms and still black damp spots bleed through new paint.
Don't know if it is a question of re-rendering outside walls, capping chimneys or poor workmanship!

Tanking behind skirting

Is it necessary to tank behind the skirting when the job is being done. Also is it possible to just do patches of tanking on a wall?

Buying first house - reasonable to ask vendor to pay for damp survey?

We are buying first house, had damp survey total cost £4728. We don't have funds to pay so have asked vendor to pay instead of reducing asking price. Would that seem unreasonable?

Damp at base of wall.

After consulting a damp proofing company about constant damp on an outside wall we discovered that the builders who built the extension 30+ years ago had placed a damp proof membrane in the floor and a damp proof course but nothing had been done to the wall between the two, so the damp was penetrating from outside. The floor was dug up and damp proofing material painted to the underside of the damp proof course.

The smell disappeared as did the salts and staining. All has been well until we looked at replacing the carpet. Where the carpet is tucked under/against the skirting board is is badly stained and has started to rot. The carpet fitter reckons it is not insect damage but extended exposure to damp. There is no staining under the carpet and testing with damp readers suggests the walls are OK. The suggestion is its the einted hint of damp that is doing harm to nothing othe than the carpet edge.

The damp proof company insist there is nothing else they can do - not in a disinterested way but they feel we'd be wasting money repeating existing treatments.

Is it worth, perhaps, removing the skirting and bring it forward by an inch or so, so any new carpet is not against the external wall and maybe insulating the void that would create?

Breast wall in bedroom

Last year had a problem with damp on breast wall from chimney stack. Roofer came out August 2013 and checked tiles, lead and soakaway identified the stacks were open and 4 cowls were fitted. I used a humidifier for 6 months to dry out redecorated the roof and everything seems to be fine until this week I saw 3 patches of damp half way down the breast wall on the edge of the breast wall. Roofer been out checked the cowls, tiles, lead and cannot see any problems. Can you please give some advise on what to do next. The property is about 100 yrs old mid terrace with joint chimney with neighbours.

The stack still remains on the roof.

Mould on clothing but not the walls


I'm renting a terraced house. It's a 3 bed with the third bedroom being an attic conversion. My partner and I decided that we would use this room as our walk in wardrobe room as it had a built in wardrobe built into one of the walls, she uses this while I use clothing rails to hang my clothes (including my collection of Stone Island clobber)

When we first viewed the property I noticed mould on one of the master bedroom walls (the separating wall to our next door neighbour). This we were assured would be professionally treated prior to us moving in.

It wasn't, it was painted over!!! We discovered this shortly after our daughter was born... The mould reappeared and despite getting onto the letting agency we were ignored. We were even forced to put our daughter at risk of Sudden Infant Death Syndrome (SIDS) by moving her into another room to sleep at 3 months old, to protect her from the mould spores. There was also another mould patch on another wall.

We contacted the letting agents who visited the property. The conclusion was that because we had the original wooden guttering it it was rotten and causing water to run down the external wall causing mould to form internally (the effected area was about 5ft in length). The wallpaper was removed and the wall was treated by 'professionals' and left bare for 3-4 weeks before being re-wallpapered.

2 weeks after we moved in the landlord arranged for workmen to come round and gut the cellar as it had a major damp issue.

Then a few months later, after the summer my partner noticed mould on a number of pairs of her (leather) shoes stored in the built in attic wardrobe, this she found was spreading to her clothes too.

A short while later I noticed that my clothes were riddled with mould too and a horrifically bad mouldy/earthy smell filled the room. What struck me as odd was there was no mould on the walls/roof etc, just clothing

What is causing mould to form on clothing but not walls? I know for mould to form in leather there has to be 70-80% moisture in the atmosphere but as the damp specialist was sent by the landlord/letting agent and he's not concluded that there's an issue with the property they aren't willing to get the mouldy clothes dry cleaned. The damaged clothing cost £11,000 and they seem to think I've purposely put mould on them to get them dry cleaned!!

Also the mould on the master bedroom walls which was professionally treated... That's back now too!!

Any help would be much appreciated.

Airbrick height

My airbricks were level with ground for over 5 years, also no insulation in the external wall so when we cut off the plasterboard, you could see day light. Could this cause condensation damp?

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