Help! Advice for severe mold in fireplace

[Charlotte H]

Hi Everyone,

Bit of background... we have recently bought a 1750s cottage. We are trying to be sympathetic with restoration however we are on a tight budget. Unfortunately the outside of the house is cement rendered but we can't remove this yet due to cost/ unsure of condition of stone underneath. Roof has been redone and is now watertight. Chimneys are capped.

Our current puzzle is what to do with this mold damp fireplace! It's on an external wall. The previous owners cupboarded it in. We've had it open to try and dry it out and have been dehumidifying it but are a but worried about the mold spores. We've tried mold spray and vinegar and scrubbed it with stiff and wire brushes but this is the best we can get it to. We won't be using it as an actual fireplace as gas pipes run through but maybe as a wood store for a woodburner elsewhere.

We were thinking of possibly sealing the bricks but not sure if thats the rught thing to do or whether to ecocork? But want to get rid of the mold first. Any tips or advice on how to proceed would be amazing!

 

[DaveG]

Hi, I think you’re on the right track by opening those doors up. Mold can only survive in dark damp places. Keep the light and warmth getting to it and monitor it on a weekly basis. It can take some time if that wall is full of moisture for it to start to dry out.
What does the wall look like externally? Has it been rendered? Is the pointing visible? Is it in good condition? Is the wall damp from other issues such as leaking guttering?
I wouldn’t suggest sealing the bricks. Better if there is moisture there that it’s allowed to escape
Usually when a chimney is sealed up there should still be some ventilation maintained and I don’t see any in this case. Possibly something to explore in time but interested to see if you can get this area dried out firstly

 

[Cubist]

As you've already pointed out the exterior has a full coat of cement render. This in effect is preventing the house breathing as effectively as it might and all the moisture rising through the masonry walls, the floors and your own activities is being trapped indoors. You best long term solution is to get rid of the render but this is not an option for the moment. Your best immediate term strategy is to get rid of those doors forming the cupboard to allow and support enhanced air movement to carry evaporated moisture away from the old fireplace. The increase in air movement and lighting will ultimately kill off any mould whilst also drawing out the salts - some of which I'm sure you are seeing - from the brickwork. Anti-mould treatments may help a little but time, air movement and light are your best weapons here - until you can get rid of the render.

 

[mardinor]

Are you absolutely sure that's mould? The black stuff looks like old soot/tar deposits to me.

 

[Charlotte H]

Hi, I think you’re on the right track by opening those doors up. Mold can only survive in dark damp places. Keep the light and warmth getting to it and monitor it on a weekly basis. It can take some time if that wall is full of moisture for it to start to dry out.
What does the wall look like externally? Has it been rendered? Is the pointing visible? Is it in good condition? Is the wall damp from other issues such as leaking guttering?
I wouldn’t suggest sealing the bricks. Better if there is moisture there that it’s allowed to escape
Usually when a chimney is sealed up there should still be some ventilation maintained and I don’t see any in this case. Possibly something to explore in time but interested to see if you can get this area dried out firstly

Thanks Dave, will try and let it dry out and take out the moldy old board blocking the chimney, maybe replace it with new one with a few holes to allow a breeze through. Outside is cement render which unfortunately we can't afford to do anything about at the moment. Its in our main living area so ideally want to get it looking more aesthetically pleasing, is there anything you can think of we could do to it once it's dried out that wouldn't affect the breathability?

 

[Charlotte H]

As you've already pointed out the exterior has a full coat of cement render. This in effect is preventing the house breathing as effectively as it might and all the moisture rising through the masonry walls, the floors and your own activities is being trapped indoors. You best long term solution is to get rid of the render but this is not an option for the moment. Your best immediate term strategy is to get rid of those doors forming the cupboard to allow and support enhanced air movement to carry evaporated moisture away from the old fireplace. The increase in air movement and lighting will ultimately kill off any mould whilst also drawing out the salts - some of which I'm sure you are seeing - from the brickwork. Anti-mould treatments may help a little but time, air movement and light are your best weapons here - until you can get rid of the render.

Thanks for the advice! We wish we were in a position to get the render off but hopefully in time to let the house breath. The old owners also put down a cement floor! So there is that to unpick too!
Will air the cupboard, change the board to a vented one. Unfortunately it's in a but of a dark patch natural light wise. It's also in our main living area so once it's dried out is there anything you could recommend to make it a little more aesthetically pleasing that allows breathability? What about insulting it?

 

[Charlotte H]

Are you absolutely sure that's mould? The black stuff looks like old soot/tar deposits to me.

A lot of it seems to be mold, it smells like mold and scrubs off but maybe you're right, the more stubborn bits could be old fire residue

 

[DaveG]

Once properly dried out, you may be able to retain the doors if you were happy to cut some vents into them, especially if then there’s some air movement up into the stack.
Dry it out first then you could try vents but if it starts getting damp again you may need to lose the doors and “dress” the fireplace? A small iron fire basket with some logs?

 

[Cubist]

What about insulting it?

I don't think that shouting abuse at it would be at all helpful. But, on the other hand you might find it a little de-stressful.

The black stains on the rear wall are most likely old soot and tar deposits from wood or coal burning but black mould cannot be absolutely discounted. The white/grey stains on the side walls could be mould but could also be salts being pulled out of the masonry by the warm air now circulating in that space.

If all else fails you could consider hiring, or even buying, a cheap sand blasting tool to clean the surfaces of the bricks - but you would need to be careful not to damage the mortar while doing so.

In terms of aesthetics, your idea re a log store is a good one but I would suggest you use one of those triangular frames that would allow air flow below and all around the logs. A better idea I think, that definitely appeals to me, would be a wine rack. Now that would be de-stressful.

 

[a twig]

Once you’ve cleaned it up as best as you can a couple of coats of limewash will go a fair way to slowing down any return of the mould