Rising Damp?

freddykrueger

I've been searching through the historical threads here just for some advice but can't find anything that fits exactly.

We bought an ex local authority house a couple of years ago - at the time the survey did not flag up any moisture readings and once we moved in the whole house was re plastered. This involved bricking up an old fireplace and then plastering this (effectively the chimney breast wall in the living room).

I have subsequently noticed some salts coming through the plaster close to the skirting and looking at the other side of the wall (I can do this as it is a terraced house and there is a shared close through to the back gardens) it is evident that it is on both sides. The neighbour seems to be having similar problems.

The question I have is how do I find out the root cause and get this treated - I'm terrified that it is going to cost a lot of money that I just don't have. It is possible that the chimney is not capped but this is the only reason that I can think of - the floor in concrete.

Thanks is advance for any advice or opinion - the plaster has not blown yet as far as I can see but will obviously need to be redone if and when I can treat the problem.

phill99

Have you put in ventilation when you blocked up the chimney? It js essetial that there is a through flow of air through the chimney. Blocking up the fireplace and not putting a vent in will mean that you get a moisture build up that the wind is not clearing. If you install a vent in the base of the chimney, this should clear the problem.

freddykrueger

phill99 wrote: »

Have you put in ventilation when you blocked up the chimney? It js essetial that there is a through flow of air through the chimney. Blocking up the fireplace and not putting a vent in will mean that you get a moisture build up that the wind is not clearing. If you install a vent in the base of the chimney, this should clear the problem.

It was actually the plasterer that bricked up the fireplace then plastered it over. To my knowledge there is no visible ventilation (apart from that coming down the chimney) - how easy would this be to do?

Thanks for your help.

David_Aldred

Hi,
Chimney breasts / fireplaces are great when used for what they were originally intended - i.e. having a roaring coal fire within them. When this ceases to be the case they can be problematic for a number of reasons.

Soot from the original coal fires tends to leach into surrounding masonry and this is high in sulphates that are disruptive to many plasters. In addition the hearth itself may lack a damp proof memebrane beneath it as there was often a reliance upon the heat from the coal fires keeping the hearth relatively dry. When this ceases to be the case and no damp proof membrane is present the hearht becomes damp with ground moisture and this migrates into the fire-back and the infill material behind the fire-back thus forming a moisture resevoir. The situation is compounded on party wall fireplaces that are back to back. Contaminated plaster will not recover. Taking out redundant fire-backs / infill material, if necessary re-casting the hearth on a suitable damp proof membrane linked into the surrounding damp proof course in the walls and correct substrate preparation / re-plastering to a specification able to hold back salts within the wall often help. If the house was built with a damp proof course (dpc) then statistically this is unlikely to have failed significantly other than any minor cracking to it with settlement. Kindest regards, David Aldred Independent damp and timber surveyor

freddykrueger

David_Aldred wrote: »

Hi,
Chimney breasts / fireplaces are great when used for what they were originally intended - i.e. having a roaring coal fire within them. When this ceases to be the case they can be problematic for a number of reasons.

Soot from the original coal fires tends to leach into surrounding masonry and this is high in sulphates that are disruptive to many plasters. In addition the hearth itself may lack a damp proof memebrane beneath it as there was often a reliance upon the heat from the coal fires keeping the hearth relatively dry. When this ceases to be the case and no damp proof membrane is present the hearht becomes damp with ground moisture and this migrates into the fire-back and the infill material behind the fire-back thus forming a moisture resevoir. The situation is compounded on party wall fireplaces that are back to back. Contaminated plaster will not recover. Taking out redundant fire-backs / infill material, if necessary re-casting the hearth on a suitable damp proof membrane linked into the surrounding damp proof course in the walls and correct substrate preparation / re-plastering to a specification able to hold back salts within the wall often help. If the house was built with a damp proof course (dpc) then statistically this is unlikely to have failed significantly other than any minor cracking to it with settlement. Kindest regards, David Aldred Independent damp and timber surveyor

Thanks for your post David - the property I believe was built circa 1950. There is no hearth present just a concrete floor - can I assume from your post that this would be an expensive repair?

David_Aldred

Hi - thanks for the kind words, the making good should not be expensive if and it is an 'if' you can find a good tradesman who can address the points raised and re-plaster to an appropriate specification that is both waterproof and able to hold back the disruptive contaminates. Some of the major manufacturers of specialist plasters / additives and wall preperations will usually be pleased to advise whoever you employ on the correct use of such products which you can purchase direct from them such as:

Safeguard Chemicals - Redkiln Close, Redkiln Way, Horsham, Sussex, RH13 5QL (tel 01403 210204) www.safeguardeurope.com

Wykamol Group – Unit 3, Boran Court, Network 65 Business Park, Hapton, Burnley, Lancashire BB11 5TH (contact tel 0845 4006666)
www.wykamol.com

Sovereign Chemicals – Park Road, Barrow-In-Furness, Cumbria. LA14 4QU (tel 01229 870800 )
www.sovereignchemicals.com

freddykrueger

Thanks David - would this involve injecting some kind of chemicals into the brickwork and then using a special plaster?