High humidity and mould

[musttryharder84]

We have a problem with mould in our house. It’s mainly our items that go mouldy (coats, shoes, books, dining chairs, wooden cupboards). We do get mould forming on a couple of external walls but it’s not awful.
We bought several hygrometers and they say the humidity is 90% 😮
We never have condensation on our windows, or any water/damp on walls which I’d expect at 90% humidity. It doesn’t feel humid to me but we bought an expensive dehumidifier, and this also gives a reading of 90% humidity. It runs non stop and if we’re lucky it gets the humidity down to around 70% but if we turn it off or forget to empty it, the level quickly increases again.
It’s a 25L one. We found some mould starting again on the wall in one room so shut the dehumidifier in that room. It’s removed 75L of water in a day.
Why the hell is this?!
I’d should maybe add that our neighbours have similar issues and we live opposite a lake. Could this be why? Are we just doomed to be cleaning mould off things and throwing our items away forever? If anyone has any tips please let me know. I just retrieved my best winter boots from my cupboard to find they are mouldy and I just want to cry, I can’t afford to keep replacing everything.

Is the house warm?
Is water getting into the fabric of the house?
are there expelairs in the bathroom and kitchen?
do you dry washing in the house.

putting silca gel in with items prone to mould will help on a small scale in shoe boxes.

I suspect water is seeping through the walls

We wouldn’t dare ever dry any clothes in the house! If it isn’t suitable for tumble drying it doesn’t get washed until the weather is supposed to be dry.
The house is warm, we have the heating on more than most probably to try to stop the mould.
We have hundreds of those little silica gel packets around, especially in shoe boxes etc and all along the back of the cupboard where our shoes go but maybe I need some of the larger scale ones (I’ve seen those moisture trap things so might get some of those too).
We have extractors in the bathrooms but those never have a problem with mould.
We don’t have anything (apart from normal hood extractor) in the kitchen. But again this is one of the rooms that never gets much mould forming.

How would I even know if water is getting into the fabric of the house?

But if it was seeping through walls wouldn’t they feel wet?

What are the walls made of? Are they rendered? Are they cavity walls?
Do you have unused chimneys? The bricks on the stack become porous due to heat and then the water seeps down?
what are the floors made of?
do you have a wood burner or open fire as keeping it lit will help. As it’s a constant source of heat and it moves the air through the house and it warms up the chimney wall.
is all the mould forming in rooms at one side or end of the house? Try to look for a pattern which will lead you to the cause.
the heating on is good as that helps enormously.
the large silca gel things are the way to go in wardrobes and cupboards

You do have to dry out the silica gel every so often

The walls are brick and rendered. I have thought maybe the rendering needs redoing but obviously that’s an expensive job. They’re single brick though so no cavity wall. There are no chimneys and unfortunately we don’t have a fire or wood burner, just the central heating. Floors are mainly floorboards, part of the house is concrete floors.
The mould is much worse at the front of the house but 2 rooms at the back seem to be getting worse recently.

Haha I know they do. But I guess if 75L is coming from one room in a day I’m not drying them out anywhere near enough.

It’s a 25L one. We found some mould starting again on the wall in one room so shut the dehumidifier in that room. It’s removed 75L of water in a day.
Why the hell is this?!

How big is the room? Stupid question, but was the window also closed? Is there an underground leak somewhere?

Have you got the windows shut when you use the dehumidifier?

Yes the windows are shut when the dehumidifier is on.
That room is roughly 3m x 4m.
I have no idea if there could be a leak. I feel like that would explain the issue for us but then not really why all the houses have similar problems. Unless the leak is really extensive

Render is often an issue. It cracks and I hen water gets behind and the bricks get wet. And it seeps through.
guttering is worth checking as well as any flashing. Any cracks in the render will let water in but they can be repaired
When the outside of the house is dry and it starts raining heavily go outside and watch which areas of wall become wet and does this correlate to the damp inside the house.
There is a product called thomsons water seal which waterproofs old bricks I’m not sure if you can use it on render and it’s painted on every couple of years. I’ve used it on chimneys and it does work.
I think a leak is unlikely if you all have the same problem. If you have a water meter it’s easy to check for a leak but turning everything off and seeing if it still goes round
it’s a detective game finding the source of damp but it’s really worth taking the time to do.

I had this loss of furniture etc in a property with a huge damp problem. I don't believe the presence of the lake would cause this. Som sort of fault in the building.

How would I even know if water is getting into the fabric of the house?

Damp meter. From a DIY store. They're not expensive.

But if it was seeping through walls wouldn’t they feel wet?

No. Might feel cold. Room feel cold. Need more heating than usual because it's not just heating the room it's trying to dry out the walls.

All the houses nearby are rendered and all are old, so it may well be that. I’ll get a damp meter and double check. I had no idea such a thing existed!
I’ve looked up the water seal and it says it’s for use on render so I’ll get some, even if the meter says the walls aren’t damp.
I don’t have a water meter but I agree it’s probably less likely to be a leak.
Thanks so much for the ideas. Fingers crossed I can figure out where it’s coming from and fix it

Tap the render with your fingers. You can hear if there's a blown part (come away from the wall due to moisture getting underneath). If it's really bad there may be an obvious bulge in the wall (which would otherwise be flat) when you stand at the side and look down it. Painting the render with something isn't going to fix any of that.

Is the ground level outside higher than the damp proof course?
Are the gutters and downpipes working properly?
Is there a leak under the floor from the radiators or incoming service pipe?

Good point PP. Amazing how many people build up flower beds without giving any thoughts to whether they're breaching the damp course.

Also is this a basement OP? "Ground level" for this purpose means "street level" not the level of the floor next to the wall. Basement is notorious for damp, not really designed to be lived in originally and need different damp proofing measures to make them habitable.

There’s nothing obviously wrong with the render I can see, though one wall of the house is inaccessible from the outside so will be hard to sort.
I’m pretty sure the ground isn’t higher than the damp course. You have to come down a few steps when you come out the house and there’s nothing built up against it (apart from the steps themselves which aren’t very wide). It’s not a basement but “street level” is a hard one as the street is about 3m lower than our house and there’s lots of steps up to our front door. So I assume ground level has to be the level outside our wall for us.
It pissing it down now so I’ll go and check the gutters, especially outside the worst room

Check gutters and the roof space looking for leaks.

Do you own the house or rent? If you own, do you have buildings insurance that could help with identifying the source of the damp?

Link to a moisture meter

https://www.amazon.co.uk/Dryzone-Moisture-Meter-Detector-Materials/dp/B099FBZWHJ/ref=mpssa111_sspa?crid=25WLOD189XO6H&keywords=moisture+meters&qid=1667722990&sprefix=moisture+met%2Caps%2C83&sr=8-1-spons&psc=1

Sorry more questions...

Is the house terraced or detached?

What make of dehumidifier have you got? Saying that if it can remove 75litres a day it sounds like a good one. Maybe you need more than one?

Is teh prevailing wind off the lake. SEems that would mean very damp air constantly blowing towards you.
You could put the humidifier outside the door to measure the level there then compare it to inside.

The roof seems fine, it’s new and actually we only get mould downstairs not upstairs.
It’s detached. We own it but pretty sure our insurance doesn’t have anything like that with it.
It’s a Meaco 25L one. It’s great but was £300 so I’d rather not have to buy another. But also we just don’t have space for another really.
The prevailing wind is from the lake I think. The air in general feels quite damp here a lot of the time and the side of the house nearest the lake is much worse but then that could also be due to a problem with render or something else on that side. We rebuilt a lot of the back wall when we moved in and that was rendered then so probably less likely to have a breach than the front of the house

I've just bought these, worked out at £1 each.

www.ebay.co.uk/itm/18-x-LARGE-INTERIOR-DEHUMIDIFIER-DRAWS-IN-MOISTURE-STOP-DAMP-CONDENSATION/383681208644?pageci=18c34d78-7376-4f99-9a9a-e3844cc0d8d4&redirect=mobile

@Lysianthus those were exactly what I was thinking of. They seem really cheap I’ll buy them - thanks!

Just realized I’m being completely stupid with the dehumidifier and it’s only 25L not 75L obviously 🤦🏻‍♀️
The 5L tank fills within a few hours though