Damp question

[kev208]

Hi,

My girlfriend and I are close to purchasing an end terrace house. we know it has a few little problems like damp in the chimney breast leading to some small patches of damp inside on and around the chimney breast. we are going to open up all the flues (they are currently blocked) and possibly have a coal fire in one room.

however, we visited the house the other day and noticed two small damp patches on the outer gable end wall. the mortar between the stones is quite wet and was coming away. My question is, can condensation from the chimney soak outwards as well as inwards and if not, what are the other explanations for this damp and is it easily fixed? if not the chimney I'm thinking it might just be the old mortar is faulty and is letting water soak into the bricks immediately around that area.

if I repoint this area and then paint the outer wall with a water repeller will this prevent the condensation from gettin to the outside naturally and concentrate the damp inside?

any help gratefully received

[meow2222]

may be all it needs. What age is the house? The materials determine the right mortar to use.

not such a good idea. Such chems only slow down evaporation, which does the oposite of helping. Houses dont get damp if maintained appropriately, theyre never painted with such things new, for sound reason.

NT

[kev208]

It's a Victorain terrace. 1900-1905 I think. Stone walls.

[Chris Bacon]

Photos (to be uploaded somewhere, there are lots of free places)? What sort of stone, and approximately where?

[meow2222]

Right. Then you need to use lime mortar. Cement pulls the corners off the stones when it eventually comes away. Also lime allows more evaporation that cement, and ensures this evaporation (and thus salting) occurs mostly on the easily replaced lime, not the stone.

Note lime mortar contains no cement, some seem confused about that!

Also note this is the wrong time of year to do outdoor lime work, as frosts will cause it to fall apart if they occur. It would be best to leave it till the risk of frost recedes, assuming things arent so dire the wall is at risk of collapse.

NT

[kev208]

Thanks for the replies.

Follow this link for a picture, click on "my hobbies" when you get to the site.

damp patches are just under each arrow. the one on the left is about a 0.5m circular patch and the one on the right is a bit smaller. the chimney stack is between the two of them and you can judge the floor level from the windows and wall at the front.

the rest of the wall seems bone dry, its just these two isolated patches, literally like someones just spilt water on it in that one spot. the mortar was crumbling as I rubbed it though.

our main reason to worry is that the original sale of the house fell through becasue the original buyer got a builder round who quoted for =A35000 worth of work. our builder (and friend) said pretty much nothing needed doing to it and this other builder must have just been short of work!! we missed these damp patches until the other day though. I know it's difficult to say but do you think this random =A35k could be anything to do with these patches?

[Rick]

I have a half built chinmey, rain gets in the top, reaches an obstruction, and runs out to the brickwork, you can see the water on the bricks matches the height of the obstruction.

It may be as simple as this, especially if its an open pot on the top, and a bad job of riping out an old fireplace.

Over time this wet in the bricks will damage the mortar, which can be repointed.

Rick

[Weatherlawyer]

ugh because the

Our builder (and

r must have just

What are the joists like around the chimney? There may be damp coming in as well as what you have seen on the outside.

That would depend on what else you missed. Is your friend insured the way a surveyor is? And watch for dodgy get-out clauses in the surveyor's report.

You are going to need to get up on the chimney somehow and make sure that there is no debris filling it after all those years of neglect. Also check if it has a flue liner and when that was fitted if they use it for C/H.

Relining a chimney and repointing the gable, plus scaffold (and topping the chimney?) will take a big lump out of 5K. But times are a bit thin. They always are after Sickmess.

=A35000 implies =A3500 for materials. Thus after other expenses such as scaffold and tool hire, he had found =A33500 to =A34000 worth of work. That's quite a few days. How much was he allowing himself for rainy days?

You will only find out if you bite the bullet. But your biggest problem is only scaffolding that gable and sealing the chimney. You might easily manage it yourself -in case I have put you off. But it is really a summer time job for a DIYer.

(Of course if you believe in evolution you could hit it with lightning indefinitely. It's not even organic. Hmmm.... how come there are no fossil houses? Or pre-houses?)

[meow2222]

Theres no way we can know what else needs doing without seeing anything, or surveying the house. You had a survey I assume?

NT

[Stuart Noble]

I can view the picture ok.

[kev208]

Sorry about the pictures. Was in a rush and it was the only place I could find. if anyone can suggest a better free site for uploading pics please let me know and I'll put some better ones up.

we did have a survey. it identified small patches of damp internally in the chimney breast but that was it. bascially said everything else was in good condition for its age.

builder looked at the joists for the chimney and said they looked fine. chimney stack itself is fine.

[Patrick]

It's difficult to say from your photograph but, a likely explanation of your damp patches is that they are being caused as a result of the burning of fossil fuels, which has made the stonework in that particular area hygroscopic. Naturally, they will then absorb moisture at a far greater rate than masonry that doesn't have these characteristics.

Ammonium salts are produced when coal and wood is burned and these leech into the surrounding masonry. That's why chimneybreasts often show damp patches.

You can't do much about it now and, if the only problem is damp patches on the external wall, which will dry out as the relative humdity falls and evaporation kicks in, then I would just accept the fact that you have two damp patches on your wall!

They won't be a recent thing and if they haven't done any damage by now, chances are they aren't going to. As Meeow says, re-point with lime morter and don't use anything on the surface that would inhibit evaporation. Have a look at

will show you why you need lime instead of sand and cement!

HTH

Patrick

[Mark]

and its free

-

[kev208]

OK, been back to look at this. the damp patches on the outside gable end wall correspond with a damp patch in the back room. It extends from the lower right of the chimney breast to about half way acorss the right hand alcove and is quite damp.

if the mortar has perished on the outside which I have concluded it has, could the damp have permeated through to the inside and if so, is this still a matter of just re-pointing the outside and obviously putting right any damage on the inside?

could this be caused a by a fault in the damp course and if so could I claim on this as it has a 30 year guarantee?

[Stuart Noble]

Suck it and see. Try repointing and see if it improves. IME it's likely the bricks themselves are too porous in that area (the previous comment about burning fossil fuel makes sense), so the next thing to try might be a water repellant like Thomsons Waterseal. It's never worked for me but you obviously don't want to obscure such nice brickwork in any way.

Are you sure rainwater isn't pouring on to those spots from somewhere. Worth getting out there next time it pours to see if anything untoward is happening. I have a gable end wall and it appears water divides into

2 streams either side of the breast rather than running down uniformly

Worth a try. A metre up is supposedly the limit of rising damp, and it looks like yours is well within that. If it isn't rising damp, then the company's original diagnosis must have been wrong but I've never known anyone succesfully claim against a damp company. Keep us posted.

[martinbyrne56]

I have just read this chain and have the following comments. A Waterseal product will do exactly what it says on the tin and seal in the water. The trouble with this is that the water may freeze durign the winter and you will suffer terrible damage to the brickwork. I have done a lot of research intot his common problem and can recommend three products. All three are from a company called Chem Crete in the States, but are imported to the UK. They are called Pavix, Yufix and Sofix. They are water based repellants and sealers which allow the passage of water vapour out of the brickwork but not in. I used a company called Engineering Heritage for this work in the SE of England. They have an excellent understanding of brickwork and masory maintenance. Try

I hope this helps.

Douglas R

Stuart Noble wrote:

[Stuart Noble]

A one way sealer eh? Ain't technology amazing!

[manatbandq]

I presume he means water vapour out but not water droplets in. A bit like a Goretex jacket for the wall.

I still wouldn't trust it.

MBQ

[Owain]

It sounds a good idea, but wouldn't one have to be very careful to brush it on with the right side of the brush to the wall for it to work properly?

Owain

[Stuart Noble]

I know the Gortex argument from way back. Microporous paints and all that 70s stuff. Fact is, all paint will allow water laden air through it, especially when applied to a porous and variable surface like masonry where it doesn't form a proper film. The idea that you can hermetically seal a buiding with a pot of paint is faintly ridiculous. You're lucky if it even acts as a barrier to the droplets.