Damp problem

[arl]

Hi,

we have a 1890's mid terrace with damp in the dinning room. the damp is all along the internal wall between the terraces. this wall has a fireplace but the damp seems less on the chimney breast compared to the alcoves. The wall has previously had a DPC (not by us!) and some kind of cement render applied to a height of 3 foot. the damp appears exactly above this render which i am guessing is no coincidence and rises for another 2 foot. I think it may have been a problem for a while as the floor boards in this area have all been replaced and the picture rail is missing
Ive checked the air brick on the external wall of this room and that looks fine and there is nothing obvious crossing the DPC outside although the patio is a little higher than it should be (but the damp isnt on the external wall anyway).
i had a damp "expert" round when we bought the house who advised us to get a DPC and render on the lower walls but i cant see that would help.
any ideas on how to procede would be gratefully appreciated.

 

[Paul Hopper]

Hi Arl
Do not rely too much on what you were told about injected dpc's. They are only as good as the installer. Could it be that next door have something that "bridges" the supposed dpc on their side? like a brick supported sink or even a solid floor?Try to have a look if you can,
If the re plastering was done correctly (and it rarely is!) the damp shold nor really show above about a metre above skirting level, if next door is causing the problem you may have a little negotiating to do.
There can be more to this so keep us posted..
The external ground levels can cause some problems but from what you say I would doubt it, I wonder why the floor has been repaired so much.. rot possibly, try to lift a floorboard to see what is below and let us know,

paul

 

[middi]

Hi.

Are we right to assume that next door(s) have the same problem or this damp is only on your wall ?.

From what you are describing it appears that the (damp proof ?) cement render has more than likely aggravated the situation.

On a solid wall constructed with lime mortar is very easy to destroy the delicate balance of the breathing mechanism by interfering using incorrect materials.

The damp can only come from above or below the wall, apart from ensuring that there is no water entry by ensuring that valleys, gutters, pointing, chimney joints etc....are in good condition, I would be tempted to remove all that hard render an let the wall breath for a few weeks.
This would give the opportunity to check if and how any damp is travelling up the wall and then take it from there.

I now this may sound a bit drastic, unless the root cause of the problem is determined there is little point in trying to attempt remedies and hope for the best.

(It appears that someone has already done that).

 

[Paul Hopper]

Middi

How right you are.. I hope our posts will help a little but there are so many reasons for damp,including other peoples failure to read the situation. I would like to know a lot more.. as I am sure you would.

Paul

 

[middi]

All I can say Paul, I am glad I do not own a damp eradication company.

I would have to lie a lot to make any money.

To eradicate damp in old properties we could all do with " honest" experts,
these are in short supply I am afraid.
It is also my opinion that even to the knowledgeable " chap" that owns the notorious damp proof company, it would be in a conflict of interest to offer the advise.

PS.
My comments do not apply to the honest lot.

 

[Gervase]

Middi's right, there's no quick fix. You need to remove the render and allow the wall to dry out and so you can get a better fix on the shource of tha damp. Fix that and then when you replaster, make sure it's with lime plaster so the wall can breathe.
It does sound, though, as if you're going to have to get to know your neighbours very well...

 

[RobT]

Hi Arl,

obviously, not having a decent look at your particular problem its hard to come to any real conclusions.

But there is a tendency to focus on moisture from the ground.

Could moisture/rain possibly be coming from above and collecting above the DPC?

regards

Rob

 

[rshartley]

In our cottage water was penetrating through a poorly (cement) pointed wall, and through cracked roof copings. The damp was working its way down inside the wall and then appearing through cracks in cement render at heights up to 3 feet. Basically, all the damp coming down was collecting behind the render and squeezing out through the cracks. This was completely cured by repointing the wall with lime, repairing the cracked copings, stripping off the gypsum skim and one inch thick cement render internally and replastering with lime. May be you have a similar issue with water penetrating at roof height, possibly through flashings around the chimney?

 

[PC]

This is a classic problem in many properties after chemical damp proofing Im afraid!.

It sounds to me that the application of hard cement render has forced the damp further up the wall to the point where it can evaporate, also bear in mind that the upper plaster may be of a weaker consistancy and therefore more absorbent and will therefore draw the moisture out.

Where the chimneys also replastered after dpc or is that original plaster?

Add in the other issue of potential salts and that could be adding to the problem if it was that damp (salt band). I would suggest you hack off the plaster and replace with something similar to what was there in the first place.

My guess is that when you hack the plaster off it wont look that damp! If it is let us now!

New floorboards normally suggest rot or insect attack. Are the timbers bearing into the wall or on sleeper walls? Check the sub floor condensation or even free standing moisture.

Hack off the worst bay area first and give us an update as we may be able to advise further.

Hope that is of use?

PC

 

[arl]

Thanks for the replies - some very helpful advice

oh dear, looks like i will be round to the neighbours again - ive already had to ask them to sort their gutters out after the plaster started falling off in the bedroom. they will be overjoyed to see me again so soon!
Ill check the chimney and get the floorboards up at the weekend and let you know what i find, but as for taking the plaster off - i promised the OH i wouldnt take any more off till i learnt how to put it back on. Time to book myself on a course i think

 

[Matt Green]

Your neighbour's property: is it at the same height as yours? Are the internal floors at the same level?

Also, you have a suspended timber floor- is the floor on the other side of the party wall suspended or solid?

Just some things to check- I bet the lower section of your side of the party wall is earth retaining....

Matt Green

 

[Peter]

You may be able to claim on your household insurance - it's worth checking.

 

[Paul Hopper]

Arl

I am with PC here, this problem keeps reppearing with monotonous regularity. I feel sure he is right, salts are sometimes driven higher due to a hard render.Although about one metre is the nominal heighr for salting it is not unknown for it to go much higher.

Paul Hopper

 

[arl]

well it seems the wet weekend had some advantages. It looks like the flashings around the chimney are letting in a steady trickle of water. No idea if this could be reappearing downstairs without causing any signs of damp upstairs?
If this is the cause, how long before i should expect to see some drying out?

 

[rshartley]

Sounds very similar to the problem we had on one wall. The damp seems to percolate down through the brickwork and I think is only shows at lower levels because it builds up when it reaches the damp course (if you have one) or the ground. If there's an impermeable covering on the wall then if builds up until the pressure finds out the little cracks - then it pushes through them to the outside.

I think the drying out time will depend on whether or not you strip off the render/plaster. In my case, the wall behind the cement render was very wet (damp crumby bricks that in some instances were almost dissolved in the water trapped inside the wall).

After we stripped off the render we left the wall exposed for about 3 or 4 months before re-plastering in lime. I think it took a couple of months for the bricks to dry out on the surface but I would guess the damp in the middle is still drying out now and could take a year or more to dry fully. I suppose it depends on the type of brick, the mortar, the plaster and just how long the damp has been building up.