Mum and Dad have a fireplace that was fitted approx a year ago. from the start there has been a dark circularish mark that appears on the right hand side of the hearth. Think it’s made of limestone.
obviously we have an issue with the fitting agent/seller about getting this sorted and that will be put into hand soon.
But what I really want to know is what could cause such a problem. The mark was really pronounced this morning and was slightly brown with what looked like a salty looking ring round the outside as if drying out again.
Is it a deposit in the limestone that is bleeding out? or is it something in the base securing material that is bleeding up? although i would expect this to have well and truly to have dried through by this point.
it’s secured on a wooden floor so doubt it’s a water leak issue and the place that it occurs seems to be consistent with a water leak under the base. when we wiped it this morning with a cloth the mark was visible reduced so there must be something coming through the hearth.
Any ideas what could be causing this?
I will try and get some pictures

its not tar deposits coming back down round the register plate is it ?

or is it the bit of the hearth in the room its appearing on ?

It’s the visible part of the hearth approx where you’d put an ornament

Might be from the hearth being bedded down on mortar or something similar to fix and level it in place?

Pics would help. Is the salty-looking ring powdery stuff on the surface? Have you seen salts coming out of brickwork anywhere else in the building?

Google ‘efflorescence’ and you’ll see what I mean.

What sort of fire do you have?

honeybadgerx – Member
Might be from the hearth being bedded down on mortar or something similar to fix and level it in place?

Yeah this was suggested at the start but would this still be damp underneath after a year and drawing the nasties up? My Dad reckons the guy had told him that he had to build the level up on the otherside more so I would have expected the mark to have been on that side if it was a mortar issue but I’m no expert

zanelowe – Member
What sort of fire do you have?

Fire is electric so that’s not the problem.
Picture is from after may dad wiped down the hearth with a damp cloth I’ll try and get the worst picture off him today. There is definatly something coming up from either inside the hearth or under it.
it’s difficult to see on this picture but the mark started off as a mark about the size of a mug and has spread over time

i’m a stonemason. limestone is very porous, but not uniformly so. i suspect there was a tear in the dpm that went under the concrete that it’s sitting on and moisture is being drawn up through the most porous bit.
difficult to say though, i would want to lift the hearth to be sure.

jonah tonto – Member
i’m a stonemason. limestone is very porous, but not uniformly so. i suspect there was a tear in the dpm that went under the concrete that it’s sitting on and moisture is being drawn up through the most porous bit.
difficult to say though, i would want to lift the hearth to be sure.

Hi Jonah This sounds the most plausible thing but what I don’t understand is that the hearth is sat on a wooden floor and I’m pretty sure that there is an open space under it so if the membrain is split then I’m not too sure how the water is getting in under the hearth.

When I rubbed my hand over the patch my hand did smell of damp stone afterwards. Do you think the mark would go if the damp was stopped? It does have a brown tinge though.
The guy who looked at it said it’s possibly iron coming out of the limestone Not sure if this is a possibility or just flannel. I assume the concrete should be dry under the hearth after nearly a year?
Cheers for the help Steve