Omnibuswoman

Mildew all over plywood walls

Recommended Posts

We put the plywood onto the inside of our stud frame back in June/July - all seemed fine. On Friday we returned to the workshop after a fortnight away and found every wall covered in black mildew. There has been plenty of airflow in the workshop as it has no front doors as yet. Does anybody have any ideas about why this has occurred? It has been quite stormy recently (SE Cornwall), but only normal for Cornwall, and the walls have stayed dry as the building is wrapped in Tyvek.

 

There were also some part sheets of ply leaning against the walls, and where two sheets touched the ply was clear of mildew (photo 1). All wood exposed to the air was blackened.

 

How can we treat or seal this to stop it from getting worse?

mildew ply 1.jpeg

mildew ply 2.jpeg

mildew ply 3.jpeg

mildew ply 4.jpeg

Share this post


Link to post
Share on other sites

Is it not because you have no proper insulation and airtight membrane?

 

The temperature in the building is marginally higher than the outside so condensation us forming on the inside of the ply? 

 

Just a guess.

 

 

Share this post


Link to post
Share on other sites

We do have insulation in already (a novel product made from old plastic bottles that made a fantastic dog bed) but not an airtight membrane - only a tyvek membrane wrapped around the outside.

Interestingly, today we removed two of the ply sheets from the front wall and found that behind them (on the side facing the insulation) there was no mildew at all... That would support your theory about the inside of the ply having condensation forming on it, but I thought that ply could absorb and release a certain amount of moisture without any harm coming to it...

Share this post


Link to post
Share on other sites
14 hours ago, Omnibuswoman said:

...

How can we treat or seal this to stop it from getting worse?

...

 

Add just enough heat to the inside of the structure to prevent condensation.

  • Like 1

Share this post


Link to post
Share on other sites

I would stick a min/max hygrometer in there for a bit to get a handle on what is happening to the humidity. Wants to be below about 60%  iirc. About a tenner:

https://www.amazon.co.uk/ThermoPro-TP50-Digital-Thermometer-Temperature/dp/B01H1R0K68/

 

I can't remember if it is insulated at all or it has lecky, but a traditional loft heater on a timer for a bit every day might be one long term option if you can't do it passively. Something similar to this one at £16.

https://www.toolstation.com/dimplex-thermostatic-tubular-heater-ipx4/p17033

 

There may also be a suitable anti-mould paint.

 

If you replace, you could do it with hollow soffit board plastic cladding, perhaps?

 

Share this post


Link to post
Share on other sites
1 hour ago, ToughButterCup said:

Having a bad day son?

Bad fortnight, having to travel though Devon 4 times a week at the moment, and for the foreseeable future.

 

Basically, you cannot get rid of this mould once you have it.  Manage it maybe, but it will always be lurking there.

Edited by SteamyTea
I types mound instead of mould, can't think what I was thinking about.
  • Sad 1

Share this post


Link to post
Share on other sites

Mould can form on wood with dampness levels above 20%.  For internal of rooms, as stated rightly above, your RH levels should be below 60% or ideally 50%.  Looks like limited air movement (but you said plenty airflow) in that place and condensation is forming on the wood producing mould. I would get a heater of some sorts in but not a gas bottle heater as this will increase your moisture levels.  I had to hire x2 electric heaters, but word of warning - they cost a lot of money to run!

Share this post


Link to post
Share on other sites

Thanks all.

This is our workshop which at present doesn't have leccy, or front doors, or fascia and soffits, so no option to heat it at the mo, but we expect/hope to have the front doors, fascia and soffits on by the end of next weekend. This may potentially make the problem a lot worse as then the airflow will reduce dramatically, although there will be less weather coming in I would hope, and at least then it would be worth putting in some heat. However the electricity supply hasn't been connected up yet, so no source for heat in any case.

 

I'm not sure whether I should consider binning the lot and starting again with OSB, but as it cost about £600 for the ply I'm loath to be so wasteful!

Share this post


Link to post
Share on other sites

Actually, something just occurred to me about the aetiology of the mould - a month ago we moved a three piece suite and a further armchair up to the workshop which had come out of my elderly Great-Aunt's house earlier this year. Her house was full of black mould - it was a chronically cold and damp solid stone wall Victorian cottage. 

I wonder if the spores for this have come from us sitting on the sofa, and now that the weather has been quite wet it has taken up residence on our ply walls... that would explain why the inside of the ply is not affected...

Share this post


Link to post
Share on other sites

I put up an old shed that tbh I should have chopped up and used for firewood.

 

I had this mad idea to "insulate" it. In some areas there's a breathable membrane on the outside under the timber cladding. Between uprights I foam gunned.

 

2021-10-26_09-41-12.jpg.4ad7676b199d4c95a32c972b91194280.jpg

 

The thing is I put 6mm ply over this that soon went speckly and mouldy. 

 

What I did was wash down with a bleach in water solution and paint with a shed and fence treatment, chestnut I think it was. They do loads of colours, pastels etc that might suit. I'd maybe do a test panel.

 

I figure if the surface is water repellent, it's less damp thus less hospitable to mould. 

 

 

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, SteamyTea said:

Burn it and stop the spores causing asthma.

 

He means the shed, I think, not your aunt's house.

  • Haha 1

Share this post


Link to post
Share on other sites

I have a serious mould issue in my basement, which was sprayed last year with Icynene expanding foam to a depth of 130mm.  Now, the solum, after being exposed to open roof and weather conditions was in a poor condition and the liquid tar was basically gone in most places.  Anyway, after roof on and nearing completion etc, the mould growth below was phenomenal.  It was like an alien from outer space.  So, cleaned it all out and installed forced ventilation but due to the volume of it, it wasn't even scratching it and my RH (humidity) levels being above 90%, the mould kept growing, even after washing it (bleach etc) and then treating the brickwork and wood work.  So, my only option is to reinstate the solum with polythene and then a pour of concrete (polythene for my vapour barrier).  Another major project!

Share this post


Link to post
Share on other sites
7 hours ago, Ferdinand said:

He means the shed, I think, not your aunt's house.

Do I

 

Remember remember, the 5th of November

Edited by SteamyTea
  • Like 1
  • Haha 1

Share this post


Link to post
Share on other sites
8 hours ago, Ferdinand said:

 

He means the shed, I think, not your aunt's house.


To be fair, I think the house should be condemned. It’s about to go up for sale, and I think only a fool would buy it. The cottages were built for mine workers by the Duke of Bedford in the 1860s, out of the rubble dug from the nearby mines. A sort of philanthropy on the cheap. 
 

As the doors and windows have been perpetually closed since February, and there’s been no heating on, the whole place has a sheen on mildew - every carpet and wall - and the black mould is even worse than before. It’s an absolute health hazard. 
 

That said, Auntie Rene is still going strong at 94 (now in a care home) having lived in those conditions for over 55 years. Maybe it’s possible to acquire a health benefit from living in such an environment…

  • Like 3

Share this post


Link to post
Share on other sites

Lol, great response.  Your Auntie Rene has developed, over time, a hardiness which has got her to 94!  Fantastic.

  • Like 2

Share this post


Link to post
Share on other sites
2 hours ago, riboid said:

I have a serious mould issue in my basement, which was sprayed last year with Icynene expanding foam to a depth of 130mm.  Now, the solum, after being exposed to open roof and weather conditions was in a poor condition and the liquid tar was basically gone in most places.  Anyway, after roof on and nearing completion etc, the mould growth below was phenomenal.  It was like an alien from outer space.  So, cleaned it all out and installed forced ventilation but due to the volume of it, it wasn't even scratching it and my RH (humidity) levels being above 90%, the mould kept growing, even after washing it (bleach etc) and then treating the brickwork and wood work.  So, my only option is to reinstate the solum with polythene and then a pour of concrete (polythene for my vapour barrier).  Another major project!


Crikey!!!
I’m going to give washing it down and painting with antimicrobial paint a go, but am open to needing to replace it all if that doesn’t work.
 

In the meantime I’m wondering if leaving the front doors open might be a good idea rather than sealing the place up with no heating in situ yet. I’m sure it’s going to get worse. 

Share this post


Link to post
Share on other sites

Most of my life I have lived in either centrally heated, or air conditioned houses.

The one that made me ill was the 'fisherman's cottage' I had in Weymouth.

No heating that one.

 

There is a myth that bleach, which is a powerful oxidant, kills mould.  It does, to a certain extent, but it does not change the conditions that mould likes to grow in.

 

Share this post


Link to post
Share on other sites

I think opening the doors and letting the humidity equalise inside and out would be the best idea.  I have been on several projects, where they encapsulate and try (oil and gas)

to preserve items, which could be anything  from substations to equipment and more than not, the act of preservation or covering it with items actually does more harm than good rather

than letting things breathe naturally.  

 

I would certainly wash down and then treat and prior to any insulation going in they studs, get a dehumidifier in (i hired an industrial one from jewsons but I have used mega dehums in the shipyards whilst overseeing complex paint/coatings projects) and dry that baby out as much as you can once it is more or less wind and water tight.  You don't want to be locking moisture in anywhere.

  • Like 1

Share this post


Link to post
Share on other sites

Steamy Tea - exactly and my basement is 100% testimony to that.  Cleaned everything, washed it down with the right chemicals, preserved the wood and the brick, but the root cause is the solum damage, tar is gone, so I totally wasted my time getting suited and booted (tyvek masks, hepa filter vacuum etc) to clean it all up.  Reinstate the solum will resolve it all (hopefully)

 

Share this post


Link to post
Share on other sites
25 minutes ago, riboid said:

solum damage

To me, Solum is a single type of soil, which may, or may not be in layers with other soil types.

So may be missing something here.

 

But basically, once the spores are in your building, and they will be, they will find a niche and multiply.

Share this post


Link to post
Share on other sites
1 hour ago, Omnibuswoman said:

Maybe it’s possible to acquire a health benefit from living in such an environment…

 

Certain exposures can be beneficial to our immune systems but it's been documented and talked about in recent years how certain mould spores might contribute to or even lead to certain forms of dementia. Mainly the pieces are from the States so I guess we should be talking about "mold" 😂 For instance:

 

https://www.alzdiscovery.org/cognitive-vitality/blog/can-mold-harm-your-brain

 

If in doubt get rid I'd say! 

 

My old Mum was fastidious about cleaning and spent many years as a housekeeper to a few minted households. This as well as keeping on top of our house. Windows were always opened, cobwebs gotten rid of etc. In later years, after a mugging, she became quite reclusive in the home, drawing curtains, barricading doors and windows and developing an obsession with closing windows if opened. Black mould spots soon built up in the corners of the rooms due to lack of cleaning and ventilation. She was diagnosed with mixed dementia. I have to wonder whether it was the years of breathing in dust, Mr Sheen, Ajax & Vim, or the mould spores that triggered it! 😂

Share this post


Link to post
Share on other sites
1 hour ago, Omnibuswoman said:


Crikey!!!
I’m going to give washing it down and painting with antimicrobial paint a go, but am open to needing to replace it all if that doesn’t work.
 

In the meantime I’m wondering if leaving the front doors open might be a good idea rather than sealing the place up with no heating in situ yet. I’m sure it’s going to get worse. 

 

What is the RH level?

 

I might be inclined to close it long enough to dehumidify with one on a long cable, if you can.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now