Needed - Damp detectives

[plasticpigeon]

Hello old house fanatics. I am hoping someone can help with a little damp problem. I don't have a great deal of damp in my house but there is some. I am trying to work out why. I live in a standard 3 bed terrace from around 1900. The internal dividing wall between the scullery/kitchen and middle down stairs room is built off the ground and has no damp proof course. There is a suspended timber floor one side and the ground under that is very dry. The other side has quarry tiles on earth . The wall is plastered in original lime plaster on the middle room side and now has exposed bricks on the kitchen side. It did have original lime that was boarded over with plywood on the kitchen side but this has been of for a few months. I have a damp patch maybe a metre high on the plastered paper side that is almost wet to touch. On the kitchen side the bricks are very slightly damp in the same area. I can only think the damp is from condensation or the much contested rising damp. The external walls all have dpc in slate and aren't showing similar damp patches!!!! What do people think???? Also I seem to get damp on the very tatty quarry tiles floor especially in rainy hot weather. I pulled one up and the ground is dampish but not wet underneath. If I re lay clean reclaimed quarry tiles on a lime screed on the earth will I have to put up with damp on the floor in this type of damp muggy weather?? All advice would be very gratefully received.

 

[Zebra]

I posted something similar not so long ago (http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=13026 - see Flyfishers's post before we all went off and started talking about kitkats) and was helpfully advised that in sudden warm muggy weather the humid air can meet cold surfaces and what looks like damp can in fact be condensation. Could that be it?

 

[plasticpigeon]

I do wonder as the damp gets better and worse with the weather, but has persisted now for many months. It is particularly bad at the moment though.

 

[Zebra]

I know what you are going through! I've had persistent damp in my house, low down on external walls, but not on internal ones. I have tried all the usual remedies, and am finally taking the drastic measure, as advised by middi on here, of inserting a dpc (see http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=13077).
If you've not given it very much time to dry though - they reckon one month per inch thickness of wall if it's been really saturated - then perhaps it will improve with time?

 

[Keith Bowman]

I do wonder as the damp gets better and worse with the weather, but has persisted now for many months. It is particularly bad at the moment though.

So is the weather! Relative humidity of 80 - 95% here recently.
A de-humidifier might help reduce the symptoms, but I don't whether it would help identify the cause. There does appear to be more art than science in solving damp problems though!

 

[Matt Green]

Is there ever any mould on the affected plaster finishes?

M

 

[plasticpigeon]

Hello

No mould, and the woodwork around the damp is pretty sound. The ends of a couple of joists in the damp wall were a bit spongy, but actually I think that was because the ends were touching the earth floor below the quarry tiles on the other side. I have a feeling that the plaster might be damp but the brick not so damp. I should lift the floor boards to see if the wall below floor level is damp. I'm not sue it is, but the plaster on what is now bare brick was always a bit damp and very crumbly. It is puzzling. It is stuff like this that makes it hard to justify lime plaster to my partner. I have a breathable floor, bare brick on one side, lime on the other and it is still damp!!! All I can say is that if I use modern stuff, it will probably be worse, but it doesn't really cut it!!!

 

[MdB]

Lime etc can't work miracles. If the soil below is damp then that moisture will come out through the wall - that being the whole point of it being breathable. In most cases, the moisture levels are low enough that the wall appears dry. However, if there is too much, it will show as damp as it can't evaporate fast enough. With modern materials on the walls but no DPM, the moisture will be trapped which will give you higher moisture levels in the wall due to the lower evaporation levels and this will cause things like gypsum plaster to fail - as happened here to all our internal walls.

To go down the modern route may be your solution but you do need to get a proper DPM under the wall with all the hassle that entails (injected DPMs don't count).

We have the potential of a similar problem here as we have a dampish outside wall that is shortly going to become an internal wall. Our ground water table can be very high and rising damp is very much a problem in this wall. Adding a DPM isn't an option we can do so a different solution is needed. The current plan is add extra drainage to lower the ground water table and to leave a strip against the wall for evaporation. I'll be posting in a year or so's time if it doesn't work...

 

[Flyfisher]

Lime etc can't work miracles. If the soil below is damp then that moisture will come out through the wall - that being the whole point of it being breathable. In most cases, the moisture levels are low enough that the wall appears dry. However, if there is too much, it will show as damp as it can't evaporate fast enough.

Good points.

I've mentioned this before, but not for a while so it might be worth repeating. Skin usually feels dry, yet it is breathable and allows moisture to constantly escape. Put a wollen glove on one hand and a rubber glove on the other. The woolen glove is breathable and the hand will remain dry (unless it's so hot it causes excessive sweating) but the rubber glove is non-breathable and that hand will very quickly become damp from trapped moisture.

Breathable walls and finishes do not magically banish all traces of moisture but they can let it escape. As MdB points out, if there is little moisture that can readily escape then things will appear to be dry. But 'little moisture' and 'readily escape' are highly variable things. Add in many other variables such as house construction and soil conditions and it can be seen why damp can manifest itself in so many different ways.

 

[AMc]

Hello
No mould, and the woodwork around the damp is pretty sound.

If the wood hasn't rotted I'd be tempted to wonder if something has changed that has made the wall damp recently? If the wall has been damp for a while I'd expect the wood to have suffered.
My first point of call would be to check that radiator and associated pipework. It would take a lot of water to make the wall that wet but its possible.
I take it the stockcock to top up the radiator circuit is closed? An acquaintance of mine destroyed the boiler in his first rented flat by mistakenly opening the stopcock and leaving his radiator circuit at mains pressure for a few weeks.
Likewise if you have any water pipes or waste pipes nearby they might be worth a look?

 

[Matt Green]

Hello
No mould, and the woodwork around the damp is pretty sound.

My first point of call would be to check that radiator and associated pipework. It would take a lot of water to make the wall that wet but its possible. [snip]Likewise if you have any water pipes or waste pipes nearby they might be worth a look?

With a fresh water leak you'd expect there to be mould. Something must be stopping it from growing. Like ground salts.

M

 

[plasticpigeon]

Thanks for the replies. The radiator actually doesn't have any and has never had any water in it as I haven't finished the central heating yet!!!!! The water can only be from the ground or condensation. The plaster in that area was always quite wet, I think because on the other side of the wall there was a gloss painted wooden board paneling the wall. It actually wasn't mouldy, but the plaster was a bit damp and very crumbly so it was probably chronically damp. I hoped taking the board and plaster off the other side would allow it to dry out, but not much luck yet. Could it have some salts in it that attracts water perhaps???

I understand about evaporation, and was hoping that a lime finish would allow fast enough evaporation to allow the wall to appear dry, but I'm worried it may not work in this circumstance. I really don't want to mask the problem with an impermeable finish which is why I am puzzled about how to proceed. I may just wait a little longer to see if it subsides.

 

[tobydog]

"I may just wait a little longer to see if it subsides."

Drastic but should solve your problem :wink:

Only getting in there before Penners does. He must be on holiday.

I know what you mean about the ongoing battle with the other half to justify traditional methods.

 

[plasticpigeon]

Hello again

I hope I'm not boring you all with my problems!!! I have taken a couple of pics from under the floor. Actually the wall does have a dpc but I believe this is really for the joists to sit on as it is below the level of the solid floor in the adjoining room. However the bricks are quite dry!!!! The ground is a little damp. I remember the floor boards were rotten in this area but I put this down to the kitchen floor being covered with lino which extended into the corner of the room in the photos. As the kitchen was covered in lino which extended a few feet over the floor boards the ground below the kitchen was pretty wet and the boards and joists rotted at the interface between solid and suspended floor. The only thing that I have done when putting new boards down is made them fit very closely to the wall so there is no ventilation behind the skirting boards as the floor boards are so close to the wall. I think there is also caulk between skirting and wallpaper (not my doing, although we did repaint the wall with emulsion. One thought though is that the paint underneath could have been a bit glossy and therefore not very permeable). Could these be issues? Now all I can think of is that the problem is condensation of some kind or salts in the wall absorbing the water from the air. What else could it be???

 

[Matt Green]

Actually the wall does have a dpc but I believe this is really for the joists to sit on as it is below the level of the solid floor in the adjoining room.

The DPC is/was bridged by the later addition of te concrete floor in teh kitchen. Th ehous was built without the kitchen and had a DPC in the (then) external wall. The water you are looking for is under the concrete of your kitchen floor and evaporating up and out through the wall. It's brings dissolved salts with it- that's why there's no mould growth. It's not condensation and whilst there might be hygroscopic salts in the affected plaster, the cause is the bridged DPM.

I would be inclined to strip the wall back to the bricks and dry-line it. Isolating the kitchen floor from the other side of the wall seems rather drastic by comparison.

M

 

[plasticpigeon]

Hi Matt. Well you may be right about the cause, but absolutely the back extension of the house is original. The external walls have a dpc above the level of the joists as well as below. The dpc above the joists on the external walls is just above the solid floor and 2 bricks above the outside ground level which is what I would expect. The builders obviously did not carry on the dpc when it became an internal wall (which is only a 1/2 brick thick so was never an external wall). The kitchen floor is quarries on earth and not concrete, I'm certain it is original. There are 100 houses on my road all with the same back extension and the back extension is on a plan in the original deeds from 1904!!!It could have been an afterthought or change to original plans, but I'm certain done at the same time as the rest of the house. Would you still recommend dry lining? It would be incredibly inconvenient to do that as I would have to dry line around a large sash window and also would loose room from a pantry that is only around 3 ft wide