Absolutely gutted. Think I’ve bought a house with badly installed insulation

[firstbrewoftheday]

I bought my house nearly a year ago. I had a level 2 survey which didn’t show any mould issues. Cavity wall insulation was installed quite a long time ago, at least 10 years. I don’t have any certificates or guarantees for the work unfortunately. I’ve noticed recently that some of the partition walls, including the storage cupboard keep getting mould patches. This doesn’t happen with any of the outside walls. All I can think is it must be the cavity wall insulation? They are the grey polystyrene balls and always fall out when I do renovations. It’s going to cost so much to fix, isn’t it?

So it's just the internal walls? Are the mould patches at the top or bottom of the walls? are they behind furniture? Are you heating the house? Are you ventilating the house?

Mould generally grows in damp, poorly ventilated places. Heating and ventilating remove moisture from the air and make conditions too dry for mould to grow. It's often found on the inside of external walls where they are either damp from a leak outside or badly insulated and so are getting condensation on them. I can't thing of an obvious reason for it to grow on internal walls unless you have a water leak somewhere in your house?

They shouldn't be falling out as they should have been mixed with glue when they were injected. So you might end up with cold spots at the top as they settle down. But generally you can get mould in any house if there's little air movement, temperature variations, and critically, not very good ventilation.
I would say minimise drying clothes inside, use fans when cooking and showering (make sure they are clean and working) and open the windows for 5 minutes every day if you can.
A nuclear option is to buy a dehumidifier, they aren't super expensive and are very good for drying clothes.

Surely the cavity wall insulation was injected into the external cavities to keep the house warm and if those walls are dry then it's been correctly installed. If moisture is settling on your internal walls then maybe they are not insulated so a bit colder?

Are you sure you don't have a leak somewhere? My friend had problems with mould on interior wall, and it turned out to be a badly fitted pipe upstairs. As water travels, it wasn't immediately obvious that that's what it was, and it took time to track down the location of the leak.

I don’t think it is necessarily a problem. We’ve recently had that kind of insulation installed and if you make a hole in the wall some will fall out.

I don't know if it's the same sort of insulation, but we live in a 3-bed semi with cavity walls. Next door's had been insulated with polystyrene balls - not sure when but we've been here about 20 years and they sorted it about 15 years ago - they had damp problems. They got the balls removed from the cavities, I think by some kind of large vacuum machine. Much better afterwards they said. Sorry I don't know the cost, but they were very 'frugal' with their money!

It's unusual to find insulation in internal walls especially if both rooms either side of the wall are heated spaces, unless it is for soundproofing. If you do have heated spaces either side of the wall, then it's not poor insulation causing the mould, as you are not trying to keep cold outside air out so no need for insulation at all.

It's likely to be either too much humidity in the air - e.g. due to poor ventilation or things that generate damp hot air like drying wet clothes or badly vented tumble dryers - or it's a water leak into or onto the wall.

Agree with this.

Get a humidity meter. They are pretty cheap.

It could be that your living style is creating more humidity than the last occupant, that is leading to the mould.

If the humidity levels are too high then you can get a dehumidifier.

Make sure you get the right type if you keep the rooms cold. Dessicant are better than compressor at lower temperatures. The switchover point is about 15C.

If you have to get the insulation balls removed, I can tell you that my new neighbour just had a quote for £2020 (includes VAT) to get that done. It’s a 4-bed semi. A damp specialist is doing it for her.

I'd be very surprised if an internal wall in a heated building was getting cold enough to get damp forming from condensation. I suspect you've got a leak somewhere.

My dad had this problem when he came to sell the house the survey found damp in the inside walls, next door was growing weed so not sure if it was that or drying clothes on the radiators but he had to have it tanked before he could sell

Internal walls more likely to be a water leak. Are there heating pipes / bathrooms / kitchens with water pipes off the walls? Get a damp meter and if.possible check roof area above the walls, as we've had some heavy rain of late. Insulation if installed correctly not an issue, but poor installation or porous/ broken bricks will also cause an issue of water ingress.

As has already been said you don’t generally get insulation in internal walls only in the external walls of a house.

Any mould forming is more likely to be due to poor ventilation, lack of heating, minor leaks etc.

The only way to know for sure is to get someone in to have a look at what is going on.

I know a man whose has two companies. One to take it out and one to put it in. Clever fella!

Have to agree with the PP. Condensation from general living will settle on the coolest walls/windows. These are usually the external walls. This can result in mould if not ventilated enough to dry out.
Internal walls would suggest another moisture source like a leak. Unless this is downstairs & you have a solid floor? That could suggest the damp course under the floor is breaking down which is actually a bit of a nightmare to sort out.
Maybe get a damp expert out to give you a better idea.

Cavity wall insulation gets a bad rep but in the vast majority of cases there are no issues with it. It absolutely will not be causing damp and mould on internal walls. As others

CWI is irrelevant to internal partition walls so the damp must be coming from something else.

In UK homes the most common cause of damp, condensation and mould is wet washing draped over radiators and banisters, followed by long steamy showers without a powerful extractor fan. But it might be a water leak, from plumbing or the roof. Can you show some photos? Of the entire wall, side to side and floor to ceiling, and a floor plan indicating where the damp is.

How old is the house?

Is there a chimney breast in the internal wall? I have one that was bricked up and decorated before I bought the house. Unfortunately it doesn't have a ventilation brick and the wall gets damp at the bottom.

I bought a new dessicant dehumidifier for £135 in the BF sales and plugged it in next to the damp wall. It's drawing out at least 2L of water a day and blowing out wam air too, so less heating needed. If you keep your house warm already, try a compressor one. Sometimes available on Gumtree too.

"Unfortunately it doesn't have a ventilation brick and the wall gets damp at the bottom."

When you have sufficient fortitude, you can knock a hole in the bricked-up front, and shovel the rubble out, and leave a ventilation opening. For best results, break up the old hearthstone and dig out some of the rubble beneath it. There is no damp-course here so it carries damp up from the ground. Damp can travel a long way in mixed rubble, but not often more than a couple of courses in good clean unplastered brickwork. When the house was built, frequent fires kept hearths warm and dry, and the damp blew away up the chimney, but those days have gone.

Builders love hiding rubble in chimneys and fireplaces.