Damp in Victorian house dining room

[sammy.se]

Hi All,

Help needed please. I have a room in my Victorian terraced house, where damp showed up in the last six months.
This room has an external wall facing the garden, and another wall which originally was external facing, but now joins the kitchen – an extension built 15 years or so ago, before I bought the house.
The other wall is internal facing, to the corridor, and the last wall is adjoining the neighbour’s property. See diagram below.

First thing I saw was damp rising on the neighbour’s wall. I monitored for 6 months, and the damp patch was getting bigger. So I took up the and took up the laminate flooring and removed the skirting board to see what was there.
The damp was rising from the hearth (the chimney breast had long been removed before I bought the house).

Strangely half the hearth was damp (actually, the part that would have been under the chimney breast), and the hearth itself was bone dry.

The wall is not damp, and the chimneys have been removed and capped, so it’s not coming from above.

I took a floor board up, next to the hearth, near the extension wall (C), to have a look.
There is a HUGE amount of mould, and it is very damp.
The room has laminate flooring and is used everyday, so I couldn’t take more flooring up, but took some pictures.

Looking across to the opposite wall, which is a garden facing wall (A), I see the mains water pipe and gas mains, which turn into the kitchen/extension (wall C).

I thought it was a leaky main pipe, but it could be condensation. I saw no leaks, but water droplets are definitely there. I’m not sure if it’s a slow leak, or condensation.

The other thought is, that the garden facing wall is causing this – the colour of the wall looks dark, which may be damp, and it could have traveling across the foundation walls across to the opposite wall where the hearth is.

Two years ago, I dug the garden down about a foot, because the previous home owners had concreted to over the slate DPC, causing damp on the garden facing wall. That is now gone, but could the damp be traveling across the room, from the garden foundation wall??
Looking at the foundation wall from the inside, it is definitely damp, but I think the slate DPC is preventing it traveling up.

There is one air brick on the garden facing wall, which was added when the garden was lowered, but I can’t see daylight coming through – it might be a wrong position, too high, or blocked. Maybe airflow is constricted.
It’s definitely open underneath through to wall D, but maybe I need to ventilate wall B (the garden wall)? But how can I do that effectively?

Advice needed please:

1) Does it look like a leaky mains pipe to you? Or just condensation?
2) Could it be that damp has travelled across the floor that way?
3) Should I remove the concrete hearth replace with wooden joists/flooring?
4) How can I stop this problem?

Many thanks – please let me know if you need more info or photos.

S.

 

[sammy.se]

The images are high resolution, if you click them they should show you more detail - thanks!

 

[MikeG.]

I'll come back to this later, but I just wanted to say congratulations, this is the perfect way to present your questions about building issues. There are useful drawings, and some excellent photos and explanations. This is an example to anyone of how to ask for technical advice.

Dinner is on the table, so I've no time, but ventilation is obviously an issue, and condensation from a cold unlagged pipe too. More later.

 

[MikeG.]

OK, I've had a good look at this, and done my own sketches so I am pretty clear of the lie of the land.

Firstly, you say you've lowered the ground level externally, which is brilliant. It is often the first thing I ask people to do. Can you measure where it is now in relation to the floor, and tell me what the surface is now.

Secondly, we need to establish if there is a leak. Do you have a water meter? If so, turn everything off in the house......all taps, check the shower isn't dripping, that none of the taps are dripping, that the loos aren't dribbling water in (tie up the ball-cocks if necessary, and same with the header tank if you have one). Turn the central heating off. Then watch the water meter closely, and see if it turns at all. You might have to do this over an hour or two, because the movement can be almost imperceptible. If you haven't got a meter, well, it's a lot harder. You'll need to dry and clean the pipe wherever you can access it, but particularly where you suspect a leak. The more you can clean and dry, the better, because you then have to compare the dampness on the outside of the pipe over an hour or two. If it just condensation, then you can expect to find the entire pipe at roughly the same level of dampness, but if it is a leak, that should be concentrated in one area, to start with. You can test for damp with sheets of clean dry toilet paper......just hold them around the pipe for a second, then take them off and examine them. Damp is obvious.

Thirdly, can you tell me about the floor in the kitchen? I presume it is solid?

Fourthly, can you take a photo of your airbrick, and tell me roughly where it is in relation to the damp.

Finally, can you take a good look at the old concrete hearth and chimney base. Would it be possible to remove them? How much access have you got under the floor? Can the flooring be taken up and put back down again afterwards (some laminates just click together).

Two certainties: 1/ even if you have a leak, you also have a condensation issue.
2/ any solution will, at the minimum, involve lagging all those pipes and improving the ventilation.

That'll do for starters.

ETA..........no it won't!!

Can you check outside for downpipes and drains local to the wall of that room, and maybe mark them on the drawing.

 

[sammy.se]

That's great Mike, thank you for taking the time. I'll work on this tomorrow and post the answers.

Have a good night, thanks again.

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[sammy.se]

So I've spent today fixing my front door (something else that went wrong), and then taking up all the laminate flooring for further investigation.

I just need to upload the pics and type the answers to the questions above, hopefully by tomorrow morning. More damp discovered unfortunately :-(

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[sammy.se]

OK, I've had a good look at this, and done my own sketches so I am pretty clear of the lie of the land.

Indeed - diagrams help my thought process...

Firstly, you say you've lowered the ground level externally, which is brilliant. It is often the first thing I ask people to do. Can you measure where it is now in relation to the floor, and tell me what the surface is now.

Garden ground level is about 2cm over the DPC… Here is the background on the garden ground level:

When I bought the house, the garden level had been paved over twice, with a solid concrete bedding. There was visible damp along the interior walls A, E and corner F. So, I had about 1 foot removed from the garden, to get it low enough below the DPC.

We hit an issue – the original underground clay soil pipe was fairly close to ground level, much more so than in my father’s Victorian house. It was only a couple of inches below the slate DPC. The builder and I remarked how odd that was, that the original house builders did it that way. (The original clay and cast iron gullies were also high, so we were fairly sure it had been done like that since the house was built).
I had the builder replace the clay soil pipe with a plastic pipe and lower it as much as we could – which was determined by the sewer pipe this soil waste pipe joined into. We could only lower it about 5 cm. I estimate it’s about 20cm below ground level now, because I can see the top edge of the 90 degree bend connected to the waste pipe.

10mm gravel was put along the garden wall perimeter, and over the waste pipe, about 30cm wide, then channel drainage on top of that, along the perimeter of the garden walls. The sandstone paving was laid on a concrete sub-base with full mortar bedding. There is about a 5mm between the channel drains and the wall bricks. Two new air bricks were added, to help ventilation. The plinth is removed up to the drain level. I thought this would be enough to prevent damp. The walls dried up inside, so I thought it had worked, but this weekend, I have found LOADS of damp, above the DPC. Below the DPC is dry!

Secondly, we need to establish if there is a leak. Do you have a water meter? If so, turn everything off in the house......all taps, check the shower isn't dripping, that none of the taps are dripping, that the loos aren't dribbling water in (tie up the ball-cocks if necessary, and same with the header tank if you have one). Turn the central heating off. Then watch the water meter closely, and see if it turns at all. You might have to do this over an hour or two, because the movement can be almost imperceptible. If you haven't got a meter, well, it's a lot harder. You'll need to dry and clean the pipe wherever you can access it, but particularly where you suspect a leak. The more you can clean and dry, the better, because you then have to compare the dampness on the outside of the pipe over an hour or two. If it just condensation, then you can expect to find the entire pipe at roughly the same level of dampness, but if it is a leak, that should be concentrated in one area, to start with. You can test for damp with sheets of clean dry toilet paper......just hold them around the pipe for a second, then take them off and examine them. Damp is obvious.

Regarding the water mains pipe: I cleaned and dried it, and over the course of 24 hours on a mild day, it remained dry. I have now lagged it, and pulled it a few centimeters away from the beam it was touching. (I think it’s called a girder? The one which supports the joists). I will check again over the next few days, but I’m pretty sure it is not leaking.

Thirdly, can you tell me about the floor in the kitchen? I presume it is solid?

Yes, it's solid. And I also discovered that the end of the dining room, adjacent to the kitchen is also solid, so the concrete starts in the dining room, from the wall that the water pipe was touching:

Fourthly, can you take a photo of your airbrick, and tell me roughly where it is in relation to the damp.

Yes, see diagram below, and more photos on the next post.

I lifted the floor boards near wall A to have a look behind the airbricks.
The original airbrick, in the middle, has a lot of paint on it, so air flow is restricted.

Behind it is very damp above the DPC. Below the DPC feels drier.

I haven’t checked below floor level of wall E yet – but I assume it’s similar. Will check later today/tomorrow.
I did check corner G, which was also very damp above the DPC, but drier below it:

The clay airbrick, behind the downpipe, opens up to a brick wall/concrete, which I didn't know when it was put in.

Finally, can you take a good look at the old concrete hearth and chimney base. Would it be possible to remove them? How much access have you got under the floor? Can the flooring be taken up and put back down again afterwards (some laminates just click together).

Yes, the laminate floor is now removed (the click type).
A few hours with an SDS and I can remove the hearth. I have 50cm access under the floor.

Two certainties: 1/ even if you have a leak, you also have a condensation issue.

Thanks, I have lagged the water mains pipe now, and will continue to check it for leaks

2/ any solution will, at the minimum, involve lagging all those pipes and improving the ventilation.



That'll do for starters.

ETA..........no it won't!!

Can you check outside for downpipes and drains local to the wall of that room, and maybe mark them on the drawing.

Downpipes… Yes, there is a down pipe right outside one of the new airbricks. I re-positioned this downpipe when I built a log store… I (stupidly) didn’t think about the effect this might have.

One last observation. This patio slab near the middle airbrick has been damp for 3 days … I noticed it this morning…

 

[sammy.se]

I hit the photo limit. Here is more clarity on the airbrick positions:

Also, there is a bottle gully directly underneath that downpipe (which is why I thought it's a good idea to position the downpipe there).


The joists and girders have been affected quite badly. I think years of damp may have caused this? At some point, after fixing the root cause, I may need to replace some of the beams/girders here:

 

[MikeG.]

Again, you've caught me rushing off...... Great photos etc, again.

There's an obvious issue with the downpipe in the corner finishing half way up an airbrick, and discharging into the air. Ideally, that should be brought down to sit on top of the channel with a shoe, or should feed straight into a pipe in the ground. As it is now, there'll be bounce from its discharge, and it's an absolute certainty that lots of water from your roof is ending up going straight into the underfloor void through that airbrick.

 

[MikeG.]

Obviously I don't have the normal advantage of seeing this in person, but the fundamentals of dealing with damp apply almost universally. I think you have 2 issues here....an ingress of water probably from the downpipe*, but also possibly from the shingle surrounding the pipe that runs parallel to the external wall (which can act as a sump for all the surface water in the area, and anything that leaks), and then condensation combined with poor ventilation helping to distribute the damp and its ill effects throughout that suspended floor area. Dealing with the downpipe is a quick, cheap and easy solution, and should be your first action**.

* It seems quite revealing that you have areas of damp above the DPC, and not below, which suggests that water is getting in at higher level and is prevented from spreading downwards by the DPC.

** Check carefully that the water runs down inside it, and not down the outside. The latter is a common fault.

One option is to remove the floor and cast in a slab with DPM. Given the other floors have already been done, this is an option, but it isn't what I would be doing.

Under all options I would be removing the old hearth. It is a cold-bridge, and obviously therefore a place for water vapour to condense. Getting all the joists etc completely clear of masonry (except where they bear on it for structural purposes), will help them dry out.

I would be maximising the air-flow under the existing floor, firstly by sorting the airbricks (& possibly inserting another) but secondly, by putting either floor vents in where the hearth is now, or, if more drastic solutions are called for, by installing a fan in that same area to force air circulation. I would certainly leave yourself an access into that floor so that you can monitor things, and you might evenmake yourself a hygrometer and check on it every month or so. It will take quite a while for this lot to dry out, but you should see positive changes by the end of the summer.

 

[sammy.se]

Thanks Mike - very helpful. I will certainly fix that downpipe asap. Airbricks will be easy to fit also, so I will do that.

As I was doing the investigations and writing this up, the thought crossed my mind whether I would need to dig out a trench alongside the exterior walls, in order to ensure the channel drain is below the DPC. Do you think that is necessary, or is the current drainage configuration ok? I could probably get it 10cm lower (8cm below DPC) I’m limited by the soil pipe height.

The reason I started thinking this way, is because of the damp in Corner G, it's really wet and a) it's far away from the hearth (no concrete connecting it) and b) it's at the opposite end of the wall to the pipe condensation, and the downpipe/airbrick. Is it feasible that damp can travel that way to that corner?

Regarding your point about the shingle being a sump – that makes sense, but how can I test for that? For example, if I inspect the footings below the DPC, and they are all dry, does that mean the shingle is not the problem?

Thanks again for your answers.

 

[MikeG.]

The thing is, given the general garden levels and all the hard landscaping, shingle is still your best answer there. The lower you can get it, the better, of course, and if you can provide a way out for any water that gets into it, so much the better.

I think the complication of damp in your circumstance is that it can travel all around that void simply in the air. It doesn't have to have a solid route to traverse because the air is so damp all it does is condense on cold surfaces irrespective of the source.

Ventilation only works when there is movement, and the fundamental issue you have is that all your vents are on the same wall. This means that when the wind is blowing onto that wall it can't really get into the underfloor void because that would require the air in there to get out....and there's nowhere for it to go. Ordinarily, it would go out of a vent on another wall. This is why I mentioned having a floor vent, or a fan: simply to get the air moving.

 

[sammy.se]

Got it, thanks Mike, appreciated. I will crack on!!

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[sammy.se]

Another question: when you say a fan, what kind are you referring to? Like an inline or centrifugal type fan typically used in bathroom extraction systems?

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[MikeG.]

That's what I'd use to start with until you've got the damp under control. It would be a bonus if you had one with a humidistat. Then a little computer fan should do nicely to keep things stable.

 

[sammy.se]

Thanks Mike. This job will keep me busy for a few weeks around my day job)...

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[NikNak]

For what its worth....

Did you lag the pipes yet.? and have you been back and had a look yet.?

The reason i ask is... my old dad (89) had a very similar problem about 2 yrs ago, except his was in the void between the kitchen ceiling and the bathroom above. We ripped up the carpet in adjoining bedroom to lift floorboards etc, and the same as the pictures in the early photos you've displayed, the pipes inc the cast iron black pipe going to the tank in the loft were covered in condensation and water droplets. We wiped them all dry expecting to see where the leak was coming from. Nope.... nothing.

In the meantime he'd been in to see his insurance agent who'd arranged for an assessor to come and have a look. Who then arranged for a plumber to come and 'sort it out'.

Plumber came and looked at it from a different angle. Turned out it was a microscopic leak coming from small section of copper pipe nowhere near a joint, and nowhere near where we were looking. The constant flow of water (albeit small) was causing the pipes to chill, and that against the warmth of the house caused the condensation etc. It was such a small hole the 'spray' of water couldn't even be seen. Not sure how he found it, but thank goodness he did. He cut out the 1/2" of dodgy pipe, replaced it, let it all dry out over several weeks, relaid floorboards, carpet etc, job done.

He showed me the piece of copper pipe that the plumber guy cut out. You had to hold it up to a bright light so see the tiny weeny spec of a hole that was there. Just a flaw in the manufacturing process of the copper pipe that then took years to become a problem. I'll ask him if hes still got it, and if he has i'll take a pic and post back here.

Hope this helps....

 

[sammy.se]

Thank you NikNak!
I lagged it three days ago, inspected after 12 hours, and left it undisturbed for 2 days - I will check tonight, and will widen my inspection to other parts of the pipe. Thanks for that info...

There is a part of the pipe that was in contact with cement - I'll inspect closely there in case there was some corrosion.

How did the plumber even spot that leak? Any clever methods?

 

[sammy.se]

The extent of the damp is quite disheartening. I'm resolved to fix all the root causes, which includes digging a channel around the exterior perimeter (as much as I can) to make sure I'm under the DPC. The previous owners also put cement render & pebble dash on the walls, not lime, so I'm going to strip that off and let it breath over the summer, then re-render with Lime (the brick faces will no doubt be ruined, so I will have to re-render to stop more water ingress I presume)

If I don't get this fixed, I won't be able to build fitted furniture against the walls, which is what I want to do.

I'm trying to not even think about the joist and wall plate damage done - one thing at a time. Sigh...

 

[toolsntat]

How did the plumber even spot that leak?

In the quietest time you can find and with good hearing, turn off all uses of water and listen for a feint sound. Closing your eyes will help.
You may not hear anything notable but after a short time get the stopgap turned off.
You, at this point may be able to hear a difference and that is possibly a leak.
We had this happen behind a wall although the noise was detected and it transpired to be a micro leak on a blanked off branch. This branch was before a newer stoptap off the festered unworkable old original stoptap.
If you want a chat PM me a number 8)
Cheers Andy