Damp Patches on chimney breast.Pic included.

pippy100

Hi,
Can anyone help?

We noticed on Friday what looks like damp patches on our ground floor chimney breast under the fire.(see pic)
The room was replastered about 5 years ago and it was recently redecorated.
The fire is on an outside wall(alleyway, we are mid terrace)
Can anyone suggest what is causing this and what to do about it?
Thanks.

ormus

more likely to be moisture coming down the chimney, rather than from the outside wall.
the liner and the capping probably need checking.
or maybe some pointing is required.

leveller2911

I'm no expert with damp but to the right of the larger damp patch there are 2 more rising from the to of the skirting board.I would check the damp coarse, make sure any airbrick are clear (if you have any) also check to see that the outside alley way pavement is about 6"(2 bricks) below the damp coarse.I may be wrong here but if it was moisture coming down the chimney you would see damp much higher up.

Before you decorated was there any patches of discolouration on the skirting boards? yellow/brown marks ? it may be a damp coarse problem as the patches look like they are rising from the skirting and not downwards....

cajef

If it was the damp course it would be showing elsewhere along the wall, as ormus says it looks like damp caused by either the liner faulty or condensation when the fire is on, a problem we had when we had a partially blocked flue in a previous house.

phill99

Its essential that there is air circulating through your chimney. If you have capped them off and have no vent at the bottom, this is the result. You need to Install a vent under the fire and putting a cowling that allows some air through on top of the chimney stack.

leveller2911

phill99 wrote: »

Its essential that there is air circulating through your chimney. If you have capped them off and have no vent at the bottom, this is the result. You need to Install a vent under the fire and putting a cowling that allows some air through on top of the chimney stack.

Phill, surely the gas fire has a vent at the bottom and would create as much air flow as a 9x4 hit n miss vent?.

I agree the the top should not be sealed off and should have a cowl fitted but i'm sure the gas fire in the photo has a vent at the bottom.Just my opinion but I think they would see a damp patch higher up the wall or even in the firt floor bedroom chimney breast, if they have a first floor...:D

If there was a back boiler previously fitted I doubt they could put a vent underneath the gas fire and it would probably be solid blockwork/concrete..

It will be interesting to see what the OP can dig up.

phill99

leveller2911 wrote: »

Phil, surely the gas fire has a vent at the bottom and would create as much air flow as a 9x4 hit n miss vent?.

I agree the the top should not be sealed off and should have a cowl fitted but i'm sure the gas fire in the photo has a vent at the bottom.Just my opinion but I think they would see a damp patch higher up the wall or even in the firt floor bedroom chimney breast, if they have a first floor...:D

If there was a back boiler previously fitted I doubt they could put a vent underneath the gas fire and it would probably be solid blockwork/concrete..

It will be interesting to see what the OP can dig up.

Because there is no gas pipe, I wasn't sure if this was gas or one of those electric fires that are supposed to look like coal fires.

If there is no through vent, any moisture in the chimney will be collecting at the bottom of the chimney. I'm open to correction though.

boogiemaster

I had the exact same fire and the company took out the flu liner and installed a clay pot thing on the chimney.

Its a gas fire the pipe is hidden and we had the same problem when rain came down the chimney.

We took ours out as the bloody fire cost us a fortune it was called a roaster it should have been called pre payment metre time.

My dad paid about £1800 for it installed but we ended up putting in a canon gas miser in the end.

pippy100

Thanks everyone for your replies so far.
The fire has been in approx 15years and is a gas fire.
We have had a look outside at the chimney stack this morning and we have a cowl, so assume the venting is o.k.
But we did notice that perhaps the mortar and the flashing may need repair/replacing in the sense that it looks like there is no mortar(but diffiicult to see).
We will now be getting in the loft to see if there are any signs of damp.

But as some of you have said if it was the chimney would it not show higher up.
Having no knowledge of this sort of thing, my first fear was 'rising damp'.
We will do some more investigating and report back.

Thanks again.

pippy100

Oh, by the way. The fire is rarely on and we have only just been putting it on since noticing the damp patches to see if they helped to dry it up.

Not working though.

pippy100

Quick update, no signs of damp in the loft and no signs elsewhere on the chimney breast other than what we can see in the picture.
Could it really be from the chimney stack having poor flashing?
Would a building surveyor be the best person to have a look at this?
Thanks.