How to diagnose the source of damp

[Wayno99]

Bought a house about 10 month ago, moved in around October with no problems and no signs of any problems and the survey came back fine.

Since moving in a large number of patches have appeared in some rooms of the house and I am assuming they are caused by some form of damp.

I really don't know how to start diagnosing this, started by getting a roofer to look at some of the roof and they did not think this was the source of the issue an I don't know where I turn to.

House didn't really need anything doing to it when we moved in as had been recently renovated (within the last fee years) but I have turned my hand to a few jobs but this is beyond anything I am comfortable with.

House is approx 1850 and walls are about 500mm thick, I think survey said random rubble construction, so far as I know the previous owners did not have this issue but I can't say for sure.

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• Wayno99
• 17 Jul 2014
• 1

Untitled

• Wayno99
• 17 Jul 2014
• 1

Untitled

• Wayno99
• 17 Jul 2014
• 1

Untitled

• Wayno99
• 17 Jul 2014
• 1

Untitled

• Wayno99
• 17 Jul 2014
• 1

 

[roy c]

It looks like there is a chimney on the walls with the damp I would check that out then if so have a look and see if there are any "Caps" on top of the pots .This will stop rain coming down into the chimney. Also I would check the outside wall for any cracks ,large or small. Also get the flashings on the chimneys checked out . Also see if the slates kick over the side of the gable wall or there is a mortar capping covering the edge of slates that doesn't over hang the gable wall. I have had the same problem as you in my bedrooms and my house is also thick rubble walls and built in the 1800'S..

 

[Wayno99]

Thanks for the replay, any help is much appreciated as I have no idea what to look into.

I will get out and have a look at the slates tomorrow, looks ok from ground level but I will get up a ladder and see.

The chimney breast in the pic is only in one room that is getting the marks, that's the dining room, they are actually on another wall without the chimney breast in the same room aswell.

The chimney has actually been removed from the roof, attick and bedroom on the first floor but the chimney breast was left in the dining room, was all done by the last owners so maybe they left it in as a feature in there.

There is a chimney on the opposite side of the house too in a bedroom and living room on that side of the house and neither of these Rooms have had the Same problem.

Do you know what is causing the problem in your bedroom ?

 

[roy c]

The problem with my house were the chimneys not being capped and lots of cracks on my gable and the slates not over hanging the gable end and the mortar fillet on top of them breaking down and cracking and letting water thru. , which l have temporary fixed till l can get at it to sort it out properly.(my neighbour is an r sole and he has made things awkward for me at times) but thats another story...I also ripped my ceilings down (lath and plaster) and knocked all the sand and lime mortar off the walls and re set the ceilings at 2400mm instead of nine foot and insulated it and I put 2" polystyrene against the walls then put Gyproc metal framing in front of it and filled that with insulation and boarded it, I have took photos of all I have done and hope to get around to loading them on my albums soon. I lost about 5" off two walls but there was 2" of plaster on the walls before so I only lost about 3". I am not saying you will have to go to this extent but over the years I have done this in every room in the house, Now got to tackle the problems outside properly,!!!

 

[Bedrock9]

Some of the issue could also be from deposits of sulphur from the actual chimney, these tend to show through as a really noticeable yellow staining rather than just damp looking. I have these on two chimney breasts but also the wall in the middle of the two chimneys which has obviously just soaked a lot of it up too. You can use a neutralising solution on the wall to try and prevent this acting as a salt and drawing moisture from inside the room.

 

[Bedrock9]

Actually looking at it again, looks like they have dot and dabbed the wall and it's bridging the adhesive dabs. Is it plasterboarded? Tap the walls to see if they are all hollow, and if they are very flat. If it is then it wouldn't be sulphur I suppose and I might be sending you on the wrong track. Roy probably sounds on the money

 

[Wayno99]

I have had a look and it is plasterboard and sounds very hollow behind it.

I have not yet been able to get up a ladder to look at the render higher up the wall as it looks fine around the areas where these marks are appearing.

The roof doesn't seem to have any obvious defects, but I am going to see if I can take some photos when I manage to get a big enough ladder.

One of the walls seems to be render and the other pebbledash, but with larger darker and more sparce pebbles than the kind you normally see.

Thanks very much for the posts, I feel better just knowing that I am starting to investigate this, i really don't just want to redecorate and/or ignore these marks.

Thanks

 

[Bedrock9]

Yeah if it is dot and dab should be hollow. It's just quite a common way to hide a damp problem.

Roy's advice on finding and curing weak points in the properties defense like bad pointing, slipped roof tiles, leaking roof, unvented chimneys (it might be capped but generally it is advised to vent it as well) etc is all good.

As for whether the plasterboard will be dry out or whether the damp spots will keep appearing due to salts I couldn't say, but did you get a more thorough valuation than the lenders basic one when you bought it?

The lenders basic survey is not normally something you have a right to pursue the surveyor for damages on because it is generally only legally of benefit to the lender, and they won't want a court case over something like that.

If you got a more thorough survey, I would think they should have mentioned that dot and dabbed walls on an old property could be hiding gremlins. They claim they're damp meters can read moisture levels beyond just surface coverings, so were you advised on getting a damp and timber report at all?

 

[Bedrock9]

Actually ignore the chimney stuff, if it is only downstairs and is open like a sort of fake fireplace then what is left is vented. If the damp is upstairs, it's probably coming in through things like flashing pointing etc like Roy said.

 

[Bedrock9]

One more thing, I suppose it could also be condensation, I imagine the dabs will be colder as they are touching the external walls.

So in theory if you aren't ventilating the property well enough it might explain why these have appeared now whilst your in there and not when the previous owner was. If the plasterboard and finish to it were not brand new when you bought the house, are you leaving windows open etc, perhaps worth getting a dehumidifier in there and where are these rooms, what is the proximity to things like showers, kitchens where a lot of moisture will be?

Just doing a Columbo. Just one more thing!

 

[Wayno99]

Finally had some people look over the patches, roofer said the roof was perfect so water wasn't getting on that way.

The outside render appears to be fine too.

The plasterer I have now had round thinks that it is because the previous owners have not accounted for the walls being solid and not a cavity wall, on a solid wall he said he would always put an insulated layer and a damp proof layer in before the plaster board, rather than just putting the plaster board straight into the walls.

The bits that are damp are mostly the bits where the plaster board has been 'dabbed' to the wall with the adhesive or what ever has been used, and it causes both a cold spot on the wall for condensation but also draws any moisture on the solid wall through into the paint work etc.

The recommendation was to redo it all proply for the external walls but that it is all fine for the internal walls and it's fine for the bits of cavity wall I have on the extension.

 

[Bedrock9]

I think I would hack off a piece of plasterboard over a dab and see if the dab was actually moist all the way back to the wall, and make sure you test ventilating the house and see if it dries out first.

Would be an expensive fix to re-plaster the whole lot and find out it was condensation.

A good guide would be if you get up in the morning before any heating comes on and touch one of the spots and see if it actually has surface moisture on it rather than just feeling damp. If it has moisture on the surface and dries out after running the heating for a bit it could well be more condensation than damp.

Especially as if your house has sound cement render on it, then this would likely have waterproofer in it and probably limit the amount of moisture in the wall quite a bit. If it was condensation, then insulating the inside of the house would stop it appearing as a cold spot on certain parts of the wall, and leave it condensing most likely on all your window sills and groundfloor skirting and rotting that to death.

 

[Wayno99]

That's great advise and is muh appreciated

I have never noticed any water or moisture on the walls, they never really feel wet to the touch either, at most the just feel cold to me.

I originally thought it was condensation as the rooms that are affected are one that have now had their chimney removed and so no longer have a fireplace which must have reduced the ventilation, all the rooms have PVC windows with no trickle vents installed and they re rarely open ( couple of hours a night) as we are on a fairly busy road so there is a noise element but mainly as we're not in all day at work so leave them closed for security, we don't have a problem in the rooms with the wood burnering stoves still in so I thought this was because they are providing some additional ventilation.

But after having the guy in to look it sounded sensible that it was coming through the 'babs' but I don't want to spend the money doing it if that will only cause another problem.

 

[Bedrock9]

Hi Wayno,

It is a sensible cause for the problem, but if you did that work anyway (insulating the walls etc) then definitely worth getting a decent dehumidifier before hand and running that when the windows are shut, and see whether it dries out.

Once it's insulated etc it will be even more airtight in theory so any condensation that was going on would potentially be worse. Or just fit a few trickle vents.

It's basically bloody hard to know for sure whats causing stuff until you try it and see. Leaking water pipes also should be well investigated before hand and especially if the walls where it is all fall in a sort of vertical line of adjacent walls. You might have a leaking pipe in the top corner of your loft or something like that. Have a good root around up there too.

I just had a ton of water pouring down the inside of my no longer damp house after the gutter downpipe disconnected at the top and it was pouring right down through two course of bricks. sods law!

Good luck anyway.

 

[Mattatooi]

Someone else posted this on here. I just saw you said your house is 1850. Might be worth looking at these videos. Very useful.

http://www.webvu.co.uk/spab/