Hello,

This is my first post so please bear with me...

I have recently bought an old detached house (approx 100 years old) and have noticed some blistering of some of the plaster next to the fire place in the living room. I have also recently noticed the same is starting to happen next to the fire place in the dining room (which is along the same wall). I believe that there is a damp problem which may be causing this. Also inside the dining room fireplace, I have just found that one or two bricks are starting to rot a bit about a foot above the floor.

My first thoughts were that we'd need a new DPC, but I was looking through the report from the survey we had when we bought the place and the guy seems to recommend that all need do is replaster the affected areas inside and also patch the external rendering. There is evidence of previous chemical damp treatments (new DPC?) having been done before and some internet research has led us to believe that this should last for quite some time. Does anybody have any ideas as to whether this is correct?

My main worry is that if we don't get a new DPC (and just replaster and patch the outside render) that the problems may get worse. Does anybody have any advice on this please? Also, would it be wise to completely remove the rotting brick and replace it, or would it be ok to leave it in place?

Final question, does anybody know why this problem is only really being noticed around the fireplaces? I should point out that the fireplace in the dining room is sealed off.

Thanks.

Hi,

Basically as the fireplaces aren't used anymore they just get damp and obviously with the top open water does eventually get in, also it's an area were the air will not circulate unless you have sufficient ventilation ie air bricks.
Also as it being over 100 years old there obviously wasn't adequate dpc's around then so usually as the fireplace is a big lump of masonry if it gets damp it will retain it.
Chemical dpc's are ok, and do perform adequately if installed correctly, but the real key is to keep the area well ventilated and carry out any remedial works to damaged render/pointing externally and also try to divert any water away externally from the base area, because any dpc will be ineffectual if you have water running down from above or settling in that area

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Hi there,
Burning coal fires produce a range of sulphate salts. These salts deposit themselves in the brick, stone and plaster. The sulphates attract moisture from the air. so the only way to stop the salts attracting moisture, which presents on the plaster is to create a barrier between the substrate and the air.

It can be achieved by renewing the plaster. The replacement plaster should have a "drywall additive" mixed in to the bonding coat. It is wise not to wallpaper over the plaster for at least a year. This allows the wall to dry out through the plaster.

Another option is to strip the plaster, and install a cavity drainage damp proof membrane. After this is installed, you can bond and skim directly on to the mesh.

I would still suggest having a specialist double check the source of moisture, using a protimeter. Their surveys are either free or £50-£60. It will give you the peace of mind that it is only a sulphate problem and not a sulphate/ water penetration problem.

Hope this helps

Alan