Rising Damp

[Fred]

Hi,

I have recently had a damp problem and have had to have my damp proof course done using the chemical type of damp proofing where it is injected into the walls. All looks fine except around the chimmney breast which is an inside wall and is adjoined to next door. At the base of the wall and about 18 inches up from the floor the wall surface on the new plaster looks soaking wet still after 5 weeks and has powdery salt like deposit forming there. My question is this, how long does it take for the wall to dry out fully and can the plaster still look wet even though it is dried out fully? I am at the stage where I want to re paper now but I don't want to paper if it is going to come off again.

Thanks.

[Phil Anthropist]

By soaking wet, do you mean wet with water or damp proofing injection fluid? Was the area that is now soaking wet, dry or only slightly damp before damp proofing was done? The installer usually says don't paint/wallpaper for x number of weeks. What did they tell you? You can either call them back to advise, which I think is advisable, or wait until the surface dries out enough to decorate.

[Andrew Gabriel]

It took my chimney breast about 3 months to dry out after removing the source of damp and leaving it ventilated well in hot weather, unplastered.

Yes. It shouldn't have been plastered until it dried out. If the salt deposits keep reappearing when brushed off, then it's certainly still damp. If you have an electonics test meter, you can push the probes into the plaster an inch or two apart, and see if you get a reading on a high resistance setting.

A common source of rising damp in fireplaces is the infill in the base. It often had no damp course because regular fires kept it dry, and it will bridge the damp course in the brickwork. I dug mine out down to the brick damp course (slate), and remade it with a damp proof membrane, vermaculite base, and thick mortar top so it could still be used for fires in the future.

[Don Spumey]

I know it's the worse case scenario, but by any chance does your fireplace have a back boiler? In older properties these have sometimes been left in situ.

Obviously, there are water pipes to and from these monstrosities and an over zealous (unwary) damp proofer can damage them whilst drilling the injection holes!

Don.

[Fred]

Thanks for the input guys,

The damp man told me to wait about 6 weeks before decorating and it is about that now. The plaster looks as though it has been put on about 4 hours or so to look at it. It is only about 18 inches up from the wall and in the one spot as I said. I don't thionk it is the injection fluid because I had to have 2 rooms done and it's only this one spot where it still looks damp, the rest looked dry after only a week.

I have wiped all the salt deposits off and drawn a pencil line around the edge of the damp line and will keep my eye on it for another 2 weeks or so before I call the guy back. I don't really want to call him back as I did have a spot of bother with him through dragging his feet and not turning up etc...

Thanks again for your time replying guys.