Damp Wall Corner in Bedroom

FlipperThePriest

Hello!

The bottom corner of one of our bedrooms (both external walls, cavity filled) is doing a fair bit of sweating. The room (and house) gets ventilation from opening windows daily. Despite no vents installed, the relative humidity in the house is usually pretty good. Even so, condensation forms on this corner, few pics linked below.

To try and combat it, I've had a fan on the corner in question and a 220w dehumidifier in the room for a few full days. Even still, condensation forms when it's cold in this corner in the morning. This is the only problem area in the house.

Initially I thought maybe it could it be an issue with the damp proof course. I read online to tape a bit of plastic to the problem area - if condensation forms on the wall side it's an issue in the wall / floor, if it forms on the room side then it must be in the room / temp / humidity. Tried this and there was a slight bit of condensation on the room side of the plastic, none between plastic and wall.

Maybe it's just that this part of the wall is significantly cooler?

Could the cavity insulation have missed this corner? Maybe blocked by lumps of concrete and dirt in the cavity? Hence the colder surface? You can see from the pics that the gable wall is longer than the side wall of the house, I wonder if there is possibly a thermal bridge here? The floor is also an uninsulated concrete slab, this would probably contribute.

Cavity was filled 10 years ago, long before we moved in. I got in contact with the installer. He said if it's needing a fill in that corner he'll do it for free. If it's already full, he'll charge a call out fee of €250... this without giving any suggestions or advice. It would be a steep box ticking exercise. I get the impression it would be €250 either way.

I toyed with the idea of getting a borescope and having a look before getting back to the installer. Also thought maybe a bit of expanding foam might do the trick. Could this be too aggressive for an enclosed cavity?

Any ideas?

Pics:
https://ibb.co/FhDm35C
https://ibb.co/mC51D3B
https://ibb.co/xHLBphj
https://ibb.co/RPhLptm (example of work from installer's FB page)
He may have even installed the vent on the gable end of our place? It's external only.

listermint

1. The room needs a vent. you won't get a cavity fill done today without adequate ventilation being done beforehand or during the install. Grants won't be issued if this is not done.

Random opening of windows is simply not going to cut it.



Yes you probably have a void in the insulation. It could be drill out and spot done.

You could also have draught coming down behind the plasterboard making that section of wall colder than the rest.


Moisture sits on the coldest part of the room it can find your goal has to be to let the moisture escape its easiest path and to lesson the cold spots in the room.

FrancieBrady

Extending that downpipe into the actual outlet would do no harm either.

listermint

Hold on theres a vent in the pictures. Didn't see them attached originally.

You I presume have underfloor ventilation.

I'd garner you have a cold spot in the corner of the floor.

Is the floor to sub floor insulated?

ednwireland

FrancieBrady wrote: »

Extending that downpipe into the actual outlet would do no harm either.

this -that drainpipe is running water straight onto the wall, extend it to the drain see if it makes difference - might take a while to dry out though.

noticed a damp patch in my own house where a gutter needs cleaning / fixing this morning !

listermint

The drainpipe should be extended into the shore. Yes definitely

It's not however the source of the problem it's. Below the DPC. Your floor should be above the dpc.

Meaning water has a stop. I don't agree that its the source of the problem.

FlipperThePriest

listermint wrote: »

1. The room needs a vent. you won't get a cavity fill done today without adequate ventilation being done beforehand or during the install. Grants won't be issued if this is not done.

Random opening of windows is simply not going to cut it.

If the room was overly damp you'd imagine the window would be laden with condensation. This isn't really the case. Maybe very slightly around the bottom on occasion, but very seldom. I agree though the ventilation isn't ideal but I'll often leave windows on the latch throughout the day. The plan is to eventually install mhrv, might not be in the next year or 2 though.

listermint wrote: »

You could also have draught coming down behind the plasterboard making that section of wall colder than the rest.

Moisture sits on the coldest part of the room it can find your goal has to be to let the moisture escape its easiest path and to lesson the cold spots in the room.

There is no plasterboard or internal insulation. This is just block wall with cavity filled.

listermint wrote: »

Yes you probably have a void in the insulation. It could be drill out and spot done.

How can I fix this. Is it worth paying €250 for the original installer to potentially tell me it was fine in the first place. Like I said, I was thinking of drilling a hole and getting a lend of a borescope.

FrancieBrady wrote: »

Extending that downpipe into the actual outlet would do no harm either.

It usually is extended into that drain. I have temporarily pulled it out and diverted rainwater away from the house and drain, just in case the drain was filling too high. You can't see the diversion in the pic as I've removed it to show what's going on around the corner. I don't think it's a damp issue coming from outside.

listermint

How was the wall finished if there was no plasterboard put on it ?

FlipperThePriest

listermint wrote: »

Hold on theres a vent in the pictures. Didn't see them attached originally.

You I presume have underfloor ventilation.

I'd garner you have a cold spot in the corner of the floor.

Is the floor to sub floor insulated?

I really don't know about underfloor insulation but I doubt it. Solid slab. Construction is from 1978 if that helps? I imagine the vents were installed when the bonded bead was filled into the cavity no? I could be wrong here too.

FlipperThePriest

listermint wrote: »

How was the wall finished if there was no plasterboard put on it ?

Just plastered. Whatever was standard in 1978 for a cavity wall.

FrancieBrady

Is the path original or added later?

Looks like someone has tried to fill the gap between it and the wall.

FlipperThePriest

FrancieBrady wrote: »

Is the path original or added later?

Looks like someone has tried to fill the gap between it and the wall.

Are you talking about the blackish / dark brownish bit toward the bottom of the plinth below?



I think this is just the previous colour of the plinth. The path is original but there are a few a few cracks and gaps at the wall, you can see some soil and growth. It may need to be removed and filled too.

FrancieBrady

zippy84 wrote: »

Are you talking about the blackish / dark brownish bit toward the bottom of the plinth below?



I think this is just the previous colour of the plinth. The path is original but there are a few a few cracks and gaps at the wall, you can see some soil and growth. It may need to be removed and filled too.

Yeh..looked like bitumen to me, but can see now it might be previous paint. No harm filling those gaps, repeated freezing/thawing of water in them will do a lot of undermining of the concrete.

FlipperThePriest

listermint wrote: »

Hold on theres a vent in the pictures. Didn't see them attached originally.

I missed this previously. As per OP, these are just external vents, they don't vent into the room. I'm not sure how bonded bead insulation works but maybe these were added by the insulation installer as far as the cavity?

I suppose to reiterate, as you say maybe the case is that the corner does need a spot fill. As I said he'll do it for free (if he missed it the first time). If it turns out it's already full, he's going to charge me €250 for a call out.

Is it worth this? If I could do it myself I would. I might borrow a borescope and drill in to see what's going on in there. Is expanding foam a bad idea for a spot fill? Or is there less aggressive spray foam for the DIYer for this purpose?

listermint

zippy84 wrote: »

I really don't know about underfloor insulation but I doubt it. Solid slab. Construction is from 1978 if that helps? I imagine the vents were installed when the bonded bead was filled into the cavity no? I could be wrong here too.

The vents would be to ventilate the cavity itself. They should be on the origin house rather than added by he installer

If the job was done correctly then bead should be visible up to the vent.

Removal of the vent could tell you what the state of play is like on that corner of the building with the cavity.

FlipperThePriest

listermint wrote: »

The vents would be to ventilate the cavity itself.
Removal of the vent could tell you what the state of play is like on that corner of the building with the cavity.

Cheers, yes I could try removing the vent and poking around into the corner.

Looking at his fb page, I could be barking up the wrong tree, looks good.

listermint

Hmm....

The holes are rather high and too few for full fill.


I'd be concerned about missing the lower half of the wall.

There should have been holes tow or three feet from the ground level.

Open the vent and have a look could stick a scope on there too

Also why didn't he go up to the ridges !

Mine where done floor to ridge. Also had more holes than that.

whizbang

The extended part of the end wall, where gutter is attached, is just too small to be anything other than 9"cavity block.

You need to pull out that vent, and find out exactly what construction you have.

FlipperThePriest

whizbang wrote: »

The extended part of the end wall, where gutter is attached, is just too small to be anything other than 9"cavity block.

You need to pull out that vent, and find out exactly what construction you have.

It's cavity wall alright, not sure why the gable wall juts out there, strange. The builder also built my home house, similar construction. I opened the vent last night, there does seem to be bead right down to the vent, all be there a bit of space down to the left (which is toward the corner, but I'll need to go in with a borescope at the weekend to see if it's significant. Can't feel enough by hand, too tight.

FlipperThePriest

Did a bit of digging around at that vent. There is a bit of space there. I've moved around the bead a bit trying to feel about. The gap used to be further down to the bottom left but I've drawn in pencil below where it is now. The second image pointing to approximately where the interior condensation is occurring. i.e. top of plinth is about floor level, then skirting, then damp spot.

There might be enough air getting in there to cool that corner causing condensation on the inside? I was thinking I could just fill this space at the vent with rockwool?

listermint

It's it's that small I would use a large expansion foam with a directable nozel so you can get right in there.

The vent has to go it serves no purpose now I'd say beading is falling out of it leaving voids behind. Probably happened in other spots too.

FlipperThePriest

listermint wrote: »

It's it's that small I would use a large expansion foam with a directable nozel so you can get right in there.

The vent has to go it serves no purpose now I'd say beading is falling out of it leaving voids behind. Probably happened in other spots too.

There's some sort of filter inside the vent cover, I assume to stop the bead escaping. Yeah suppose I could just fill with expanding foam right out to the exterior, finish it with a bit of filler, removing the vent altogether. There are only 2 of those vents on the whole house, both on this gable wall, the other is at the far side of the gable, strange. The other vent doesn't have a removable cover, it's screwed in, and the screws are beyond unscrewing. Would have to break it off.

FrancieBrady

Fill out the vents as suggested but keep the face plates and replace them. Would look better than a dodgy bit of filler that will never match in no matter what you do. Drill the heads of the screws on the obstinate one.

listermint

FrancieBrady wrote: »

Fill out the vents as suggested but keep the face plates and replace them. Would look better than a dodgy bit of filler that will never match in no matter what you do. Drill the heads of the screws on the obstinate one.

Yeah I kinda meant the vent hole. Should have been explicit. Vent cover can stay.