Damp Marks on chimneybreast

[Nicola Bhattacharjee]

Hi, since wallpapering my living room these dark marks have appeared on my wallpaper. They were a lot fainter to start with but now darker and bigger. It shouldnt be damp as we had a damp proof course done 12 months ago.
Anyone have idea what this is or how to deal with it?

 

[JohnD]

Looks like damp in the other flue. Which floor of the house is this?

When you say you had a new damp course, do you mean you paid someone to inject chemicals into the wall? What was the reason you did that?

Chemical injections do not cure condensation, leaking pipes, or leaking roofs.

Is that a gas heater in the fireplace? What sort of flue has it got?

 

[Nicola Bhattacharjee]

We had to have a new damp course as it was listed as defective on a damp survey when we bought the house. It's an electric heater so there is no flue coming off it

 

[Nicola Bhattacharjee]

And it's bottom floor! Thanks

 

[JohnD]

House buying surveys are often inaccurate on the reason for damp and therefore an appropriate cure. What did it say about damp?

Your damp patch seems to extend about a metre above the floor so is probably being supplied by a source of water. It also appears to be localised. Is it an outside wall? Do you have similar damp patches on other walls?

Is the upstairs fireplace blocked up? Is there a radiator or pipe upstairs?

Disused chimneys need to be ventilated top and bottom or they will become damp inside.

Where do you dry your washing?

Have you got a water meter?

The chimney or roof may be leaking. If you can get into the loft you may see traces.

 

[Nicola Bhattacharjee]

The chimney isn't blocked up, it was swept before Christmas. There isn't a radiator or pipe above it. Defective damp courses are a common problem on the estate and the damp surveyor recommended a new course

 

[JohnD]

Do you mean the chimney for the upstairs room was swept? Each fireplace has a separate flue, even though they are built next to each other in one chimney breast.

Such a lot of damp might be caused by a water leak under the floor. Can you see or sniff under it?

Or by rain. Is it an external wall?

Which other walls have wet patches?

 

[Nicola Bhattacharjee]

It doesnt smell, and no not an external wall. Mainly just either side of the fireplace. A small amount has appeared next to the doorframe by the speaker

 

[Nicola Bhattacharjee]

There's only 1 chimney

 

[JohnD]

So the wetness appears to be associated with the chimneys.

Relevant points may be (see my earlier questions)

Upstairs fireplace. If there is one, then the chimney will contain two flues.

Rain

Ventilation of flues top and bottom

Wet washing

If it were to be a water leak, a water meter can help detect it. You would only detect the smell of damp under the floor if you lifted a board or sniffed at a hole like the one that old pipe comes up.

Old houses often had a back-boiler in the fireplace with pipes buried in the wall.

 

[bobasd]

it looks like the hearth stones have been laid on the wood finished flooring - perhaps the finished flooring has been laid on the old soil, hearth infill - this could eventually cause damp conditions.

more immediate you have damp signs whether from rising damp or hygroscopic chemical damp i cant tell.
does your chimney flue have ventilation bottom (above the elec fire) and top?

its probable that the gypsum (wrong) plaster thats been used will have to be hacked off the chimney breast and the back walls - and replaced with (the correct) sand and lime render. you dont use gypsum plaster in damp remedial work.

whats the condition of the wall decorations on the other side - back to back with the chimney breast?

in photo 9 there seems to be a capped off gas pipe? wrong - redundant gas pipes should be disconnected at source not left stubbed out.