damp

[mike]

We live just outside St.Junien and have a moderately old (1900) brick built house. Our problem is that we have some damp in one or two walls. We know that damp is a problem in this area and we have been told that it isnt rising damp but there seems to be a bit more than is the norm. Can anyone help. If you have had this problem how did you cope with it and how did you go about getting it fixed. Is there a specialist in the area that we can talk to that can help without advising the use of a damp course (apparently not a good idea). Basically any comments thoughts and pointers would be very much appreciated.

[Théière]

What's causing the damp?

How do you know its not rising damp? is it coming up from the ground or damp patches on the walls mid way or indeed from the top of the wall downwards.

A damp course would not be a good idea if it wasn't rising damp. 

You need to decribe in detail or diagnosis is not possible.

[mike]

Now thats an interesting question. Dont know whats causing the damp but there is a lot of it in the local area. Although we are relatively high there are a lot of natural ponds and small lakes around.The supermarkets sell masses of dehumidifier kits. so we are aware of a problem. But ours seems rather more than that.

We had a company in that installs damp courses and after metering the wall, including the outside wall, he told us that we did not need a damp course as it was not rising damp. They said he could put one in but it didnt need it. It does appear to be coming from the ground up but cant be sure. The worst of it seems to be coming from the chimney breast in the kitchen on the ground floor where it extends about 4 feet up one side of the chimney breast and in the lower part of the other.The fire place is quite wide and has a wood burning stove installed. There is one other patch on the internal kitchen wall and that appears to be at ground level  and some evidence in a cupboard under the stairs. 

Ventilation could be a factor as could incorrect paint on the inside and outside walls maybe holding the moisture in and breaking through in patches but we dont know what paint was used or should be used on these walls.

Its taxing my brain thats for sure.

 

 

 

[jondeau]

That is quite amazing !

I don't think I have ever heard of a rep from from a damp proofing company advising a client that they don't need a dampcourse before. And that includes both sides of the channel.......

The thing about water is that it is very reluctant to travel uphill........other than by capillary attraction of course.

So asuming you haven't got any water pipes buried in the floor under the damp areas then presumably the best place to look is up. Damp on chimney breasts often comes from defective flashings or masonary at the top of the chimney.

 

JD.

 

 

[Just Katie]

If you have been told by experts that it is not rising damp then it could be penetrating damp which could be caused by a number of factors.  For example it could be rain hitting the external walls soaking through the bricks which may need repointing.  To remedy this, your cheaper option would be to repoint, plaster or clad the exterior of your house.

What are the ground levels outside your house?  If the levels are higher, then this will be the cause of moisture transmission and you will need to apply a form of tanking.

[Just Katie]

Sorry JD, I missed your post.  Yes of course it could also be a leaky pipe.  Water is very sneaky, there could be a leak in one part of the property from which the water will meander and manifest itself remotely from the problem.

[Théière]

Equally surprised that a damp course installer declined the work, they could be black balled for that, its against the code!

JD could well have a point, I have got to re work the top of my chimney as it lets water down sometimes after some bad work was done a couple of years ago.

Maxium height for rising damp is usally around a metre but depends on the height of the surroundings as Just Katie has mentioned. I am currently working to alleviate (can't cure) the damp in a flat next to the Regents Canal in london.

Bon courage

[Just Katie]

Another cause could be rain driving beneath the roof tiles.  If you have felting, it could be that this has rotted.

[sharkhunter]

there is always the chance that its a ventilation problem too, is the chimney sealed at the top or bottom ? Could be that a simple vent fitted into the chimney breast could solve the problem, got to keep the airflow going. The heat from the flue in the stack can cause condensation, make sure the top of the chimney has airflow and not sealed  around the flue

[mike]

Hi Team

Thanks for all this. I will check out the flashings on the roof,new one put on 3 years ago but as the damp is mainly around the chimney breast that could be a good reason. I will check the ventilation as I do think that circulation of air is part of it.

Any more thoughts and observations greatfully received.

[BIG MAC]

High ambient moisture condensing in the chimney possibly if a cheapo liner is being used.

 

[Théière]

[quote user="BIG MAC"]

High ambient moisture condensing in the chimney possibly if a cheapo liner is being used.

[/quote]

So back to the original question, what is causing the high ambient moisture (posh speak for damp)

[BIG MAC]

High ambient being damp in the air rather than been drawn up or through. The combustion of fossil fuels and discharge of exhaust via a chimney may promote the formation of excessive condensate in the flue. this may then pervade the structure of the chimney...which is posh speak for a device used to conduct exhaust gasses. Not sure if chimney fans are permitted in France or whether a well insulated liner would help.

[mike]

 

1.When you talk about lining the chimney do you mean a "collar" around the pipe from the woodburner to the chiney pot or literally lining the chimney with some sort of "cladding".

Forgive my ignorance if they are both one and the same thing.

And/also

2. A metal "plate" has beenfitted insulating the chimney breast would drilling some vent holes in that help to pull air through or does it need to be more sophisticated than that? (and I dont mean champagne and caviar after the polo match) 

 

[Théière]

Hi Mike,

The main types of liner available are:

Single wall stainless steel, serves to prevent the escape of gasses through a leaking chimney and now recomended to have vermiculite or similar to fill around the outside of the liner to keep the gasses warm so they escape out of the top better and do not begin to cool and fall back down.

Twin wall stainless steel, inner as above wrapped with rock wool usually and then contained inside a second outer wall of Stainless steel. It costs around 80 euros a metre compared to single wall around 20 euros a metre.

Much better obviously but is your chimney wide enough for the twin wall?

Do not drill holes in your plate (registry plate) very dangerous thing to do, carbon monoxide could get back into the room.

Now every one can give their opinion on my opinion. [:D]

 

 

[spen11triumph1]

Hi I have a small house which I think was a converted cattle store or outbuilding. Any way we have tiled floors which I understand is on a dirt floor. I have a patch of damp which I thought was rising only showing on the inside wall but that is getting decidedly worse with white powdery deposits and orange stains. The rest is just a darker shade of magnolia which feels damp. I have tried to seal it from outside but still it persists. You can dry it out to a certain extent by having the radiator on which is next to it but as soon as you go away and return 6 weeks later its back.I though I saw some tube of stuff that has capillary action to block any leaks. Am I wasting my time with this if it is wat happens with earth floors?