Wet plaster smell

[DIY-Dad]

Hello

I have a lounge, with bay window, that was skimmed two years ago and a wood burner installed with flue Etc.

When it rains there is a strong smell of wet plaster/ musty. There are no signs of damp. I actually think it smells bad when it is humid. E.g it really stinks today and the humidity is 86% on bbc weather. It can also smell worse if the windows are open?

My question is where do I start? Do I have chimney inspected as I worry the stove installation may have caused a problem. Could it be dpc issues? Could it be the bay window (tiled roof). Could it be drain pipes? Could it be the paint/ poor seal of the plaster?

I have searched the net and cannot find a conclusive answer to solve the problem so advice is greatly appreciated.

Thanks

 

[^woody^]

Do you have a timber suspended ground floor?

Solid or cavity walls?

 

[DIY-Dad]

Yes timber suspended and I think cavity walls - house is 1950s......

 

[^woody^]

In the absence of any actual visible damp, the most likely culprit is excess moisture under the floor.

Check that, and if there is suitable underfloor ventilation/airbricks

 

[nebjamin]

OP, I have noticed exactly the same issue in my house. I'm pretty certain it's not related with underfloor ventilation as I can smell it in rooms which are on the first floor.

I have had 3 rooms skimmed (in gypsum) over the last 3 years or so. Whenever it's humid (normally humid in my youngest's room as she normally has a soggy nappy in the morning!!) I can smell a wet plaster smell. At the moment it's prominent in all 3 rooms, 2 are on the first floor.

My guess is that since it's so humid at the moment the gypsum plaster is absorbing some of that humidity hence the smell. Was worried that I had a roof leak or similar but no sign of it and it's too much of a coincidence for it to be the same in 3 rooms which have all been replastered over the last few years.

 

[dormermike]

I get a similar thing, a vague smell of wall paper paste in some rooms on wet or humid days.

I think the suggestion that the plaster has salts or something that it reabsorbing moisture from the air sounds plausible.

I wonder if the water based paints these days contribute to it.

 

[^woody^]

If you are smelling damp plaster in rooms with solid floors or upper floors, especially where walls are decorated and not bare plaster, then you have way too much humidity and lack of ventilation.

In most cases, the smell is not of plaster, but of mould spores.

 

[nebjamin]

Well, it is bonkers humid at the moment. The thermometer was showing internal 23 degrees/68% RH external 18 degrees 90%. I'm no expert but these are about the same absolute humidity.

 

[^woody^]

Well, it is bonkers humid at the moment. The thermometer was showing internal 23 degrees/68% RH external 18 degrees 90%. I'm no expert but these are about the same absolute humidity.

Today's humid air is not settling into your walls, as the walls won't be at their dew point for air to condense.

 

[nebjamin]

As I said, no expert... seems odd that I only get this smell in the 3 rooms which have been skimmed within the last 3 years. All the other rooms (which have render), no smell.

 

[scruffybiker]

Could well be hygroscopic salts in your plaster. My lounge has patches that appear through the wall paper on humid days.... check Peter ward out on YouTube... he knows his stuff!

 

[scruffybiker]

If its also an old property with solid walls they shouldn't be skimming the exterior walls with gypsum plasters. Ideally lime based plaster. Breathes

 

[nebjamin]

If its also an old property with solid walls they shouldn't be skimming the exterior walls with gypsum plasters. Ideally lime based plaster. Breathes

I have external insulation, which is weatherproof and completely non-breathable so I don't think this is necessarily true in all cases.