Dry rot - the return

[beckyem]

Hi all, I've been reading advice on this site since I started renovating my cottage three years and I wondered if someone might be able to advise me on a recurring case of dry rot...

In May I saw mycelium poking out from under the skirting in the corner of my living room. I called a company and they quoted for treating the affected area. (I can hear the collective groans, but I panicked!) When they cut back the plaster, they told me it would be easier to re-plaster the whole wall rather than match the botched job the previous owner had done (the whole house has been a botched job, so I 100% believed them...)


There wasn't an obvious moisture source, so they chemically treated the entire wall and re-plastered it.




Today I had a carpet fitter in, and when he pulled back the sofa - more mycelium.



I've phoned the company, and they'll redo the treatment under the guarantee. But I'm kind of miffed as to why it's come back so quickly and what I can do to stop it from happening again. I know my neighbour had dry rot a few years ago on the opposite side of his house (which I thought he'd sorted), so I've asked him to check our shared wall for any sign. These houses are generally damp, but there's no obvious water ingress. I'd hoped I was slowly drying the cottage out by installing heating, removing a LOT of laminate flooring, and repointing in lime. But no such luck!

The company are coming back to have a look this week, so any thoughts, insight, or alternate advice is welcome.
Thank you in advance!

 

[malcolm]

If they think up extra work that requires you to pay them more money then don't do it!

Damp in walls is always because more water is getting into the walls than can get out again. No amount of chemical treatment and waterproof plasters aimed at further reducing the ways water can get out will fix that. A better solution is normally to stop water from getting in (not by waterproofing but by having effective drainage outside and makign sure external ground levels lower than internal ground levels) and provide a way out for any water that does get in.

What's on the other side of the wall? The floor looks wet in the first photo with the plaster removed. Was that due to washing down the walls or is it the moisture ingress problem?

 

[beckyem]

Absolutely - they aren't getting any more money from me...!

It's the party wall between me and my neighbour - we're in a row of terraced cottages. The wet patch in the photo is from the chemicals they sprayed the wall down with (yikes). The floor itself isn't ever damp - just very cold. I wondered if using a more breathable plaster would help at all?

 

[malcolm]

Are you on a hill with the house next door slightly higher? If that were the case then re-plastering the lower 18 inches or so of wall with lime plaster would probably be the fix.

 

[Lacan07]

Absolutely - they aren't getting any more money from me...!

It's the party wall between me and my neighbour - we're in a row of terraced cottages. The wet patch in the photo is from the chemicals they sprayed the wall down with (yikes). The floor itself isn't ever damp - just very cold. I wondered if using a more breathable plaster would help at all?

Is that a solid concrete floor in the photo? if so its more than likely bridged the original DPC and if no DPM was detailed there might be a path way for moisture to get into that wall.

 

[Matt Green]

Morning.

Right then; dry rot needs a lot of fresh water for a spore to germinate and grow and that has grown upwards from the wall floor junction. It is also not very salt tolerant and won't ever be caused by ground water ingress- it needs a lot of fresh water. Plumbing leaks, rainwater goods, roofing faults and the like will get you dry rot (Serpula lacrymans) whereas; ground water is more likely to result in outbreaks of anything other form of brown rot decay fungus, cellar rot being the most common.

I suspect your neighbour knows more than they are disclosing.

That wall should not have been plastered, particularly not after being soaked in water-based fungicide. Masonry takes about an inch a month to dry and it would have been better to have have a brick feature wall for a year rather than put any covering on it. Take the skirting board off, for sure, and don't attach any timber to the base of that wall. An inorganic tile upstand or similar to hide the wall/floor junction gap might look better than leaving the skirting off but it would need to be removeable so you can check what's going on behind it.

All you can really do is let the wall dry. If you want to remove the gypsum plaster, fine, but lime plaster will put more water in the wall and it will take longer to dry. Don't paint the wall with anything. Don't do anything for a year and try to make the room look as reasonable as you can whilst the wall dries. Very few companies sell a product called 'leave it alone and wait for it to dry out' so few tend to specify it.

M

 

[beckyem]

Thanks to everyone for their input on this.

Matt - this is really informative, thanks for taking the time to reply. I agree - there is certainly information being withheld by my neighbour, which is disappointing. I would have absolutely been on board with the temporary-brick-feature-wall-for-a-year, to let it dry fully, so I'm kicking myself for not consulting the forum at the time.

I'm pretty sure they put a timber frame against the brick, then plasterboard, then gypsum. Is having all that wood butted against the wet wall a major cause for concern? If they are removing a fair chunk of the plaster to investigate the area, I wonder if I just ask them to leave it be* and let it dry out myself while I keep monitoring it? Or would the rot just take hold in other areas, that are still covered by plasterboard/plaster?

They're coming on Monday, so I'll be prepared to question their suggestions.

*They have to make it 'good' under the work warranty, but I don't want them to keep causing more upheaval with quick 'fixes'

 

[88v8]

Yikes.

I do feel for you.

Ah, so they studded the wall rather than plastering directly on it. Good.
That being the case, I would have them take everything off and leave you with a bare wall. Then tell them you want to leave it a while to ensure the rot has gone. And never call them again.

So what's with the neighbour? Leaky plumbing?

Ivor

 

[Lacan07]

Thanks to everyone for their input on this.

Matt - this is really informative, thanks for taking the time to reply. I agree - there is certainly information being withheld by my neighbour, which is disappointing. I would have absolutely been on board with the temporary-brick-feature-wall-for-a-year, to let it dry fully, so I'm kicking myself for not consulting the forum at the time.

I'm pretty sure they put a timber frame against the brick, then plasterboard, then gypsum. Is having all that wood butted against the wet wall a major cause for concern? If they are removing a fair chunk of the plaster to investigate the area, I wonder if I just ask them to leave it be* and let it dry out myself while I keep monitoring it? Or would the rot just take hold in other areas, that are still covered by plasterboard/plaster?

They're coming on Monday, so I'll be prepared to question their suggestions.

*They have to make it 'good' under the work warranty, but I don't want them to keep causing more upheaval with quick 'fixes'

If they boxed out the wall that's not so good, no wonder you've been growing mushrooms when there's no ventilation. You can get away with that in certain areas of a house but not when dealing with a damp (previously damp) ground floor wall

 

[beckyem]

If they boxed out the wall that's not so good, no wonder you've been growing mushrooms when there's no ventilation. You can get away with that in certain areas of a house but not when dealing with a damp (previously damp) ground floor wall

They put in two vents at either side of the wall. But, as my new mushroom housemates can attest to, it's clearly not sufficient...

 

[beckyem]

Yikes.

I do feel for you.

Ah, so they studded the wall rather than plastering directly on it. Good.
That being the case, I would have them take everything off and leave you with a bare wall. Then tell them you want to leave it a while to ensure the rot has gone. And never call them again.

So what's with the neighbour? Leaky plumbing?

Ivor

When I broached the subject of dry rot with them earlier in the year, they were quite cagey. When I asked them this week, they said they couldn't see anything wrong. From memory (of the one time I was in their house) and a snoop at their planning application (!) they don't have plumbing on this side of the building. So I can't imagine where it's coming from. Unless the moisture already in the wall was sufficient for it to reappear?

When it started in the corner of the room, we put it down to possible ingress from a downpipe that hadn't been able to dry out due to a lack of ventilation. But we were really guessing as there wasn't anything obvious. However this new 'crop' seems to have started on the opposite side of the room... Weird. Hopefully, if I can leave the wall exposed to dry out for a while, I can also see where any water might be coming from.

 

[Lacan07]

When I broached the subject of dry rot with them earlier in the year, they were quite cagey. When I asked them this week, they said they couldn't see anything wrong. From memory (of the one time I was in their house) and a snoop at their planning application (!) they don't have plumbing on this side of the building. So I can't imagine where it's coming from. Unless the moisture already in the wall was sufficient for it to reappear?

When it started in the corner of the room, we put it down to possible ingress from a downpipe that hadn't been able to dry out due to a lack of ventilation. But we were really guessing as there wasn't anything obvious. However this new 'crop' seems to have started on the opposite side of the room... Weird. Hopefully, if I can leave the wall exposed to dry out for a while, I can also see where any water might be coming from.

Yes, all you can do now is to expose the wall and keep an eye on it, it does take a long time for a wall to dry out.