Black mould on underside of roof felt
Discussion
I've just been up into our loft and was horrified to find what appears to be black mould on the underside of the roof felt:
(Note: The white 'strips' are where the felt is overlapped i.e. two layers and hence the inside layer is not directly exposed to the tiles on top, and I think the extremely-well-defined line is more down to trapped dirt than mould.)
I haven't been up there since last summer and I am certain it wasn't like that then (or at any time previously).
The house was built in 2007 and the felt appears to be of the breathable variety (it looks like a teabag when viewed close-up) however I am assuming that even a breathable felt can't work miracles if there's excessive moisture being generated in the house, particularly given how dirty the felt appears to be on the tile side? There appears to be no eaves ventilation (hard to tell as it's a 2.5 storey house so the top bedroom has hipped ceilings which mean the eaves aren't visible from the loft space).
We have a nearly-2yr old toddler and have also been undertaking a fair bit of building work over the last six months and so I think a combination of more vegetable steaming than we used to, extra loads of washing, great house occupation, reduced ventilation to 'keep the baby warm' etc have all contributed to an excess of moisture and it has condensed on the cold surface in the loft over the winter months.
If the above is true then I am sure we can remove the cause through lifestyle adjustment, however I am still concerned about the mould that is already present. Should I try and clean/remove it? If so, how and what with? It looks like most of the black mould spray cleaners contain bleach (to kill the mould and remove the staining?) and so wondered if this might damage the felt? Perhaps something without bleach more geared towards mould removal off fabric/furniture? If I just left it (and cured the cause) might some of it disappear anyway?
(Note: The white 'strips' are where the felt is overlapped i.e. two layers and hence the inside layer is not directly exposed to the tiles on top, and I think the extremely-well-defined line is more down to trapped dirt than mould.)
I haven't been up there since last summer and I am certain it wasn't like that then (or at any time previously).
The house was built in 2007 and the felt appears to be of the breathable variety (it looks like a teabag when viewed close-up) however I am assuming that even a breathable felt can't work miracles if there's excessive moisture being generated in the house, particularly given how dirty the felt appears to be on the tile side? There appears to be no eaves ventilation (hard to tell as it's a 2.5 storey house so the top bedroom has hipped ceilings which mean the eaves aren't visible from the loft space).
We have a nearly-2yr old toddler and have also been undertaking a fair bit of building work over the last six months and so I think a combination of more vegetable steaming than we used to, extra loads of washing, great house occupation, reduced ventilation to 'keep the baby warm' etc have all contributed to an excess of moisture and it has condensed on the cold surface in the loft over the winter months.
If the above is true then I am sure we can remove the cause through lifestyle adjustment, however I am still concerned about the mould that is already present. Should I try and clean/remove it? If so, how and what with? It looks like most of the black mould spray cleaners contain bleach (to kill the mould and remove the staining?) and so wondered if this might damage the felt? Perhaps something without bleach more geared towards mould removal off fabric/furniture? If I just left it (and cured the cause) might some of it disappear anyway?
Edited by MJNewton on Sunday 12th May 11:09
Edited by MJNewton on Sunday 12th May 11:48
Do you see mould on anything other than felt? In areas near felt or elsewhere jn house. If not, then I wouldn't worry too much.
Re cleaning, U can try to clean using very weak blaeach and water solution in a small area and see what happens.
And also get a Dehumidifier. It's great to be able to leave windows open but if it's raining with high humidity outside then not much point of windows being Open.
Re cleaning, U can try to clean using very weak blaeach and water solution in a small area and see what happens.
And also get a Dehumidifier. It's great to be able to leave windows open but if it's raining with high humidity outside then not much point of windows being Open.
Edited by xyz123 on Sunday 12th May 12:31
It's only on the felt as far as I can tell; nothing on the timbers or indeed elsewhere in the house.
We've never had a mould issue before, nor condensation, which to be honest has always surprised me given we dry washing indoors and my wife's steamer (no, not a euphemism) seems to be constantly on the go. We can definitely improve on the ventilation side of things, and indeed I've been mulling taking advantage of the building work I'm doing to install a whole-house MVHR system but that was because I like the idea of them rather than was aware of a specific problem needing solving.
I've just been up with a vacuum and found that this seems to clear a fair bit. Perhaps this is suggesting it could be looking worse than it is due to the dirt that must inevitably get drawn through the felt over time?
I've read that a solution of Hydrogen Peroxide 3% w/w can help with mould and is quite safe for furniture/fabrics so that might be a 'safe' solution on the felt. At the risk of being melodramatic, I am nervous about spraying anything on that might damage the felt - not immediately but perhaps in terms of expected lifetime?
We've never had a mould issue before, nor condensation, which to be honest has always surprised me given we dry washing indoors and my wife's steamer (no, not a euphemism) seems to be constantly on the go. We can definitely improve on the ventilation side of things, and indeed I've been mulling taking advantage of the building work I'm doing to install a whole-house MVHR system but that was because I like the idea of them rather than was aware of a specific problem needing solving.
I've just been up with a vacuum and found that this seems to clear a fair bit. Perhaps this is suggesting it could be looking worse than it is due to the dirt that must inevitably get drawn through the felt over time?
I've read that a solution of Hydrogen Peroxide 3% w/w can help with mould and is quite safe for furniture/fabrics so that might be a 'safe' solution on the felt. At the risk of being melodramatic, I am nervous about spraying anything on that might damage the felt - not immediately but perhaps in terms of expected lifetime?
Edited by MJNewton on Sunday 12th May 12:54
Did you manage to remove the mould from your roof lining? I have the exact same problem, and would be really grateful for advice on dealing with the mould. I've put ventilation and a dehumidifier in the loft, which will hopefully resolve the problem. However, I want to get rid of the pre-existing black mould on the membrane, which has a strong musty smell. I can't find any information online on how to remove pre-existing mould from loft lining. Like you wrote, I'm worried that treating it with a mould spray could damage the roof lining. I need the loft as storage space, but don't want to store things there while it's mouldy and smells of mildew. Any advice very welcome. Thanks in advance!
Apologies; I never did follow up my original posting.
I don't think it was mould afterall... I dug out some old photos of the house and it looks like it's been like this for quite some time and so, in the absence of any reason why there should be mould up there, I think it is just airborne dirt from outside. Looking on the 'outer' side of the felt shows how dirty/dusty it is - presumably due to the wind that blows through the tiles, and with it being a breathable felt with small holes in I think some of this dirt has come through the white side.
Incidentally, I did spray some hydrogen peroxide on the felt and it didn't appear to cause any damage so if you think you need to use some I wouldn't worry. I suppose you'd ideally need to sort out the root cause though otherwise it'd surely only come back.
I don't think it was mould afterall... I dug out some old photos of the house and it looks like it's been like this for quite some time and so, in the absence of any reason why there should be mould up there, I think it is just airborne dirt from outside. Looking on the 'outer' side of the felt shows how dirty/dusty it is - presumably due to the wind that blows through the tiles, and with it being a breathable felt with small holes in I think some of this dirt has come through the white side.
Incidentally, I did spray some hydrogen peroxide on the felt and it didn't appear to cause any damage so if you think you need to use some I wouldn't worry. I suppose you'd ideally need to sort out the root cause though otherwise it'd surely only come back.
VFX_Artist said:
Do you have any air flow up there?
Whilst there are no obvious soffit and/or ridge vents there is plenty of airflow through the tiles and felt overlaps. It was this, the well ventilated house below and no other indicators inside the loft (e.g. condensation, smell, contents being affected etc) that were countering against the initial concern that it was mould. It is in my nature to always assume the worse though!Edited by MJNewton on Monday 10th August 16:13
Thread bump!
I have 'mould' in my loft similar to that in the OPs original picture. However, we also store a lot of things in the roof, and none if it has gone mouldy. Roof timbers also seem OK from what I can see. So I'm wondering if it's more dirt than anything else. Any thoughts or guidance would be appreciated.
I have 'mould' in my loft similar to that in the OPs original picture. However, we also store a lot of things in the roof, and none if it has gone mouldy. Roof timbers also seem OK from what I can see. So I'm wondering if it's more dirt than anything else. Any thoughts or guidance would be appreciated.
OP here, and 5 years on and there's been no obvious difference. I think it is just airborne dirt being filtered through the felt. Still nothing smells, cardboard boxes up there stay rigid and there are no other signs of issues that I'd expect to be caused by damp or mould. The house is 19 years old this year and if there was an issue I think we would've seen a significant consequence by now.
Edited by tux850 on Monday 3rd February 14:35
tux850 said:
OP here, and 5 years on and there's been no obvious difference. I think it is just airborne dirt being filtered through the felt. Still nothing smells, cardboard boxes up there stay rigid and there are no other signs of issues that I'd expect to be caused by damp or mould. The house is 19 years old this year and if there was an issue I think we would've seen a significant consequence by now.
That's good to hear, very similar story in our roof. Felt is mouldy/dirty but in good condition otherwise and overall the loft is fairly dry. We're looking at getting solar panels installed but wouldn't make sense if the roof needs replacing soon. Edited by tux850 on Monday 3rd February 14:35
TorqueVR said:
I think the modern "breathable" underlays are quite simply crap. I'm a surveyor and I see more modern underlays like the OP's with mould than on the old fashioned bituminous ones.
exactly my experience too (I'm also surveyor). Tyvek from around 20 years ago seems to be the worst for going mouldy.Proctor Roofshield seems to be okay but is often not specced as it's a little more expensive - I make a point of insisting on it in all of my projects.
Lotobear said:
TorqueVR said:
I think the modern "breathable" underlays are quite simply crap. I'm a surveyor and I see more modern underlays like the OP's with mould than on the old fashioned bituminous ones.
exactly my experience too (I'm also surveyor). Tyvek from around 20 years ago seems to be the worst for going mouldy.Proctor Roofshield seems to be okay but is often not specced as it's a little more expensive - I make a point of insisting on it in all of my projects.
https://proctorgroup.com/products/proctor-air
Looks just like it doesn't it.
Have you seen any consequential issues arising from it? As I say it doesn't smell musty or mouldy up there and there are no signs of it appearing anywhere else. There doesn't appear to be any 'physical' structure to it either, if you know what I mean, it is more of just a discolouration.
Have you seen any consequential issues arising from it? As I say it doesn't smell musty or mouldy up there and there are no signs of it appearing anywhere else. There doesn't appear to be any 'physical' structure to it either, if you know what I mean, it is more of just a discolouration.
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