High humidity

[Stonehouse]

Good morning all

Is anyone else struggling with high humidity?

I did a post a while back as we had Mdf skirting fitted to our St Astier plaster. I put lime plaster between skirting and wall to fill the gaps. I now wish I had used caulk. We have green mould growing under the skirting in some areas. I’m not sure if it is from damp walls or if I’ve trapped moisture behind which is taking a long time to dry out (we’re about 4 weeks now) or decorating. We’re lime outside.

I’m constantly opening windows and started to run a dehumidifier in evenings as the humidity is 70-80% in the room/corners where green mould is. It’s so frustrating!

If anyone else has any tips or ideas please may you share! Thank you so much

 

[Lacan07]

That's odd, I wonder if the wall is damp for some reason? Is it prone to driving rain? Any moisture would migrate to the bottom of the wall. I'm not sure filling the gaps with plaster would be too much of disaster, others may disagree.

 

[Stonehouse]

That's odd, I wonder if the wall is damp for some reason? Is it prone to driving rain? Any moisture would migrate to the bottom of the wall. I'm not sure filling the gaps with plaster would be too much of disaster, others may disagree.

It is odd. It’s in random places too.

One wall it’s on smells damp, but not the others.

One area where it is particularly bad there isn’t much of a gap between plywood and skirting board (can’t get paper under and I can see it coming out underneath).

To my knowledge it only really appeared after decorating and lime filling the gap as I noticed two areas had mould on the face of the skirting

 

[aockenden]

Have you thoroughly checked your external ground levels with a laser level? The bottom of your walls could be perpetually damp from that.

 

[Stonehouse]

Good evening.

Thank you so much for your help. Our external levels are fine. It’s very odd. One part of the wall gets hit with driving rain that is mouldy.
Another one is internal. We did have a leak that only got sorted a year ago when we did works outside so maybe that wall is still damp at the bottom even though it didn’t appear to be damp?

 

[Stonehouse]

Good evening

The humidity has been high 70s, 80s again for the past few weeks. I’ve been running the dehumidifer.

We are lime inside and out but NHL. I understand it’s less breathable than putty so are our walls struggling to manage the moisture?

Mould appears on Mdf skirting and is still growing under the Mdf in places. I’m tempted to replace for timber but nervous about the damage it would cause. The skirting would also be glued on so I’m not sure how that would help as that isn’t breathable. I understand the old way of how the skirting was fixed, but this isn’t possible now.

Any help would be hugely appreciated. I wipe the areas I can with mould but it comes back when the conditions are right. Is there a better cleaner I could use that will actually kill it?

Thank you so much

 

[aockenden]

MDF skirting was a bad choice FYI. In the future get real wood. The moldy skirting is all on the ground floor I’m guessing? What is the construction of your floor like?

 

[a twig]

If the skirting is MDF and as wet as you say it should come off pretty easily

Got any pics of the worst affected areas?

 

[aockenden]

Also take pics of inside and outside problem areas for us pls.

 

[Stonehouse]

MDF skirting was a bad choice FYI. In the future get real wood. The moldy skirting is all on the ground floor I’m guessing? What is the construction of your floor like?

I wish I had known. It’s just oddly in certain places.

The floors are suspended timber with plywood.

 

[Stonehouse]

If the skirting is MDF and as wet as you say it should come off pretty easily

Got any pics of the worst affected areas?

The Mdf is pretty solid and secured into the wall

 

[Stonehouse]

In places if I slide paper under it comes out green. In other areas there is no evidence of mould.

I even spotted some mould inside our log burner!

 

[aockenden]

I wish I had known. It’s just oddly in certain places.

If we had used timber would the glue/expanding foam go mouldy against the wall?

The floors are suspended timber with plywood.

What is the condition of the underfloor space beneath the suspended floor? If that space is sopping wet, poorly ventilated, etc, it could be pushing moisture up from beneath and into the skirting where it then molds.

You can safely forget about this maybe being related to using NHL instead of Putty. The differences are not so drastic and the house condition should not be so fragile that such a difference causes a dysfunction unless there is some deeper issue.

 

[Stonehouse]

What is the condition of the underfloor space beneath the suspended floor? If that space is sopping wet, poorly ventilated, etc, it could be pushing moisture up from beneath and into the skirting where it then molds.

You can safely forget about this maybe being related to using NHL instead of Putty. The differences are not so drastic and the house condition should not be so fragile that such a difference causes a dysfunction unless there is some deeper issue.

Thank you so much.

I’m just surprised at how humid the house is. I open the windows and the humidity increases more.

Floors appeared fine when inspected and have insulated.

I’m tempted to see how we get on with the heating in winter and see if that helps dries out the walls a bit more.

 

[aockenden]

Thank you so much.

I’m just surprised at how humid the house is. I open the windows and the humidity increases more.

Floors appeared fine when inspected and have insulated.

I’m tempted to see how we get on with the heating in winter and see if that helps dries out the walls a bit more.

I am suspicious this moisture originates from under your floor and not from the walls. I recommend you take a thorough look under your suspended floor, critically assessing the ventilation and moisture levels under there. Good luck.

 

[Kearn]

Mention of mdf, caulk and expanding foam all raise red flags about the materials and methods used.

 

[Lacan07]

Thank you so much.

I’m just surprised at how humid the house is. I open the windows and the humidity increases more.

Floors appeared fine when inspected and have insulated.

I’m tempted to see how we get on with the heating in winter and see if that helps dries out the walls a bit more.

those humidity meters aren't a very reliable indication of how much moisture is present in the fabric of the building.

 

[DaveG]

It has been a very muggy and damp few months. I’ve found similar to you where having open windows/doors only seems to make things worse.
I do have some underlying damp issues I’m addressing but your symptoms certainly sound familiar.
This could be interstitial condensation from lack of airflow and coldspots in the room, particularly floor level. Do you have much in the way of ventilation? Is your heating cycling or are you maintaining fairly steady temperatures? Are there any nearby sources of warm moist air? E.g. proximity to bathroom, utility or kitchen?
Do you have any means to test the temperature where the mould is growing to see if the area around skirting boards is cold enough to attract/condense moisture?
I’ve noticed this last day or two with the cooler/drier temperatures outside my humidity levels have started dropping back off

 

[Eric56]

I am always in hearing about best practices for humidity levels. I am a big fan of windows open pretty much all year around. However, what to do when you open up and the the humidity rises INSIDE?
I have some rooms at 70 right now but with all windows open some of down to 64 after an hour.
I could run dehumidifers all day as well.
Is 70 too high? Or is between 60 and 70 realistic for S of England?
You read any US posts and they always talk about 40 - 45 inside.

 

[Stevers]

The UK has a humid (maritime) climate, and this is particularly evident in warm spells. Parts of the USA have a pretty arid though often cold climate.

The problem is that if it's humid outside, there's a limit to what ventilation and even dehumidifiers can achieve.

During August and early September I had a damp patch in one of my basement rooms that wasn't there all through the winter and a damp spring/early summer. It started to spread quite ominously, but a few weeks ago with the arrival of rain and cooler temperatures it all cleared up again, and if that's not counter intuitive, then I don't know what is! I think of this as 'sweating', and my take is that the moisture that is always coming through the stone (and makes paper laid against it soft) can't get away fast enough as the stone is quite a lot cooler than the outside temperature - though this makes for a lovely work environment during the summer!

My semi-basement is a well ventilated space (trickle vent plus single glazed sashes), and FWIW when I did run a humidistat down there, I regularly saw 55-65%. This I regard as pretty healthy, and not very different to what we see on the little temperature displays upstairs.

Our breakfast room is currently 80%, and the Met Office indicates 92% outside, since if it's not raining, it's about to rain. The humidity inside a house even with modest air changes will struggle to be lower than outside unless it's warmer which is true for my breakfast room currently.