Damp, taking its time

[D.M. Procida]

We had a chimney stack taken down and the back wall re-rendered in the spring. The bricks were apparently very wet ("saturated").

After some months, damp spots seem to have reappeared in the ceiling and walls that had been repainted, and paint has come off the ceiling.

I asked our neighbour - it's a semi-detached house - and he said yes, he had some damp in the same corner too, but he wasn't surprised, and that he hadn't expected it to dry out so soon (it would take about a year, at an inch a month).

Does that sound right? Is there something that will measure damp in a useful way, to find out if this is new damp making an unwelcome appearance or just old damp finding its way out?

Daniele

[The Natural Philosopher]

were the walls replastered as well? Shoulkdnt be damp on the ceiling either.

Not really enough info but I would expect that the roof over the old chimney area hasn't been properly done.

[D.M. Procida]

No, they weren't; nor was the ceiling.

Ulp.

Daniele

[Andrew Mawson]

Chimneys that have been used for open fires, particularly coal fires, will have absorbed significant quantities of sulphur compounds over the years. These sulphur compounds attract moisture, which is why demolished chimney bricks should not be reused other than perhaps for garden walls.

Unless some form of barrier has been installed prior to rendering / plastering, the damp will continue to be a problem.

AWEM

[D.M. Procida]

Is it worth buying something like - a handheld moisture meter - to masure the dampness and find out if it's getting worse or better? Are these things useful?

Daniele

[Andy Burns]

I think aldi had a cheapy in their specials on Sunday, seems unlikely they'll have all flown off the shelves yet ...

[harryagain]

"D.M. Procida" wrote in message news:1l91t8w.1c7f14a1opgb5sN% [e-mail]...

I would have expected any moisture to dry ina few weeks. Sooty marks are hard to cover. There are special paints todo this, normal paint may well fail. Is there actual water, can you see anything in the roof space? Not really enough information.

A lot depends on the detail of how the chimney was constructed. Some of them bridge the cavity in the outer wall (assuming your house has one). Water may be penerating under the roof system, a gutter may be overflowing etc. . Get whoever it was done the work back

[harryagain]

They are of limited use. They will tell if it's damp but not the reason why.

[Andy Burns]

Do multimeters tell you why there is a voltage present, or thermometers why it's hot? All meters must be useless by your logic ...

[Dave Liquorice]

Takes a very long time for a really wet wall to dry, the quoted inch a year is probably on the slow side but the rate is of that order.

After the work was completed and water tight, it should have been lefta good six months before redecorating to stand any chance of damp marks not showing through. Even then without using a "stain blocker" of some sort and the wall being completely dry the chances are the marks will still come through.

The cheap two prong damp meters are next to useless, you can make 'em read almost anything you like by how hard you shove 'em into the substrate you are "measuring".

The only thing that really bothers me is patchs "on the ceiling". Is that on the ceiling but right in the corner between wall and ceiling or a stand alone patch away from the wall? Is it in the same place as a previous stain, see above...

[Rick Hughes]

inch a month is a fair estimate .... dehumidifier would speed it up.