Rising damp in party wall caused by plaster touching concrete floor?

[Churchillian]

We have an odd damp problem, in that we live in a semi and that the damp which appears to be rising is along the party wall in both the living and dining room. When we bought the house last summer. we though the damp patches were just condensation but we keep finding more along the skirting board and rising up the walls which actually feel wet in places. The floors underneath the carpet also feel damp nearby. The other walls are fine.

Had a damp proof guy to come and look at it yesterday and he reckoned it was probably to do with the plaster in the walls touching the concrete floors underneath without some kind of membrane between them. Our house is 1950's so does have a damp proof membrane generally. He also said that it could be the fireplaces. One is sealed with plasterboard but does have a vent and the other one is open. Both have pepper pots on top.

He also said that he'd never seen a damp problem like this before in 20 years of doing surveys and advised that we need to remove a section of plaster on the lower wall of the back room - on the side and back wall and also some of the floor before he could be 100% sure what the problem is and would come back and look at it then. I'm not sure about this as it will cause a lot of mess and will be expensive potentially to replaster again.

He also said that they could add a membrane between the plaster and the concrete floors to solve the problem, if that is the problem - anyone had this done and how much did it cost? Did it solve the problem?

Do you have wet floors? If so I fail to see how the plaster touching the floors could be the cause unless there's no airflow in which case the problem is condensation, not riding damp. You can hack off some of the plaster more easily and cheaply than fitting a membrane (which will be a plastic sheet of some sort).

Was this damp proof guy offering a free survey? And selling damp proof courses? On the party wall like that it's much more likely to be rainwater getting in around a chimney stack, if there is one, or where the tiles on your roof meet the tiles on next door's roof.

Should be if not I fail to see...

I have a problem like this, not helped by someone adding a layer of concrete into the wall itself. Moisture has to get out somewhere so it rises up the plaster. I've hacked the worst sections of plaster off and the wall ia drying out, but now I have to work out if there's a way of replastering but leaving a ventilation gap somewhere so the problem doesn't come back.

so the problem is that you have a wet floor.

I will guess that it is a concrete floor.

I will guess that there is a water pipe or radiator pipe in it.

Pipes sometimes leak.

In a semi, the house next door also has pipes.

I will guess that if your damp "surveyor" didn't mention this possibility, either he started the job this week, or he wants to sell you a chemical treatment that will not address the source of the water.

How old is the house?

Have you got a water meter?

I had this in the hallway my terrace.... next doors radiator was leaking. That got fixed, the wall dried out.

As others have mentioned , don't discount a leak. I had a similar thing with a damp party wall. To cut a long story short there was a leak in the water pipe (only a small one, but probably been dripping for years) where it came into the house. It was a very old terrace and the pipe was coming in under the front door adjacent to the party wall, hence us both having mystery rising damp.

Mine was a soil pipe on my neighbours side, lead pipe probably been leaking for a while. In a previous property we had three quotes all found a different reason and we had to go for an independent damp report which dismissed all the other reasons. It again was an old lead water pipe rusting in concrete in one area and not having cavity walls on another wall.

Thanks some Interesting suggestions - the damp proof guy was from a reputable local company and was not trying to sell us a damp course. He advised me to do some further investigation myself and coming back to look again (for free) once we'd removed the skirting boards , taken off the plaster and taken up the carpet. I'm getting a second opinion tomorrow too.

I'd discounted it being a problem with the chimney and roof as there's no damp upstairs on the corresponding walls. Is it possible that a leaky roof could only cause downstairs damp, which appears to be rising up wards from the floor, judging from the staining on the walls?

Piglet John, thanks - our central heating must have been added after the house was built so all the pipes run around the walls downstairs and are not embedded in the concrete floor. The radiators and pipes are also on the opposite side of the room away from the damp areas. All of the water pipes are on the opposite/external side of the house to where the damp is and they are visible and there are no obvious leaks. Could there be drains underneath the property? There is one gutter down pipe at the front of the house which we can't see the drain to, as it's concreted in but the area near this is not damp, it's worse towards the centre and back of the house, where there is no down pipe for either us or our neighbour.

I will check with our neighbour about their central heating - the damp patches are along the whole party wall though, in two different rooms not just in one area so it would need to be a pretty serious leak.

Water finds the lowest point. Depending on the path it is taking there may be no signs of damp higher up. It can track down cables - we once had water coming in down a TV aerial cable.

a leaky drain is much less likely to make the floor wet. From what you describe the water in in the floor and soaking into the wall.

It is very difficult for water to reach the ground floor due to a roof leak, but very common due to a pipe. Sometimes an old forgotten pipe, such as a back boiler or a room that use to be a kitchen.

Is the concrete floor original to when the house was built?

Have you got a water meter?

p.s.

it's usually the water supply pipe, which runs from where the stopcock in the front garden used to be, before someone paved over it, to where the stopcock under the kitchen sink used to be, before the house was renovated and extended.

The steel pipe in a 1950's house will be pretty well rusted through by now, starting at the elbow.

Hmm, I think our stopcock is still outside - our house has not been renovated or extended since it was built apart from cosmetic changes such as new Windows. The front room floor looks original in that there's a layer of 1960's Lino under the carpet. Kitchen is in the original place on the other side of the house from where the damp is and that's also where the old back boiler must have been - the chimney is still there. The side of the house where water is doesn't have damp. I will mention it to the damp survey guy tomorrow though and see what he thinks thanks and also the roof - it's worth exploring all possibilities

We do have a water meter and our bills don't seem excessive - £21 a month for the four of us...

it need not show on the bill, but peer down at the dial with a torch. I think you will find a glass dial, with a bubble in it. The bubble will turn when water is flowing. Does yours ever stop?

Does you boiler have a pressure gauge?