How to dry out subfloor space after major water leak

[NippyNelly]

Hi all, Hope this is the right forum We've just had a major water leak in the kitchen - an old lead pipe that had been capped started leaking, and must've been running for at least a week before I spotted it (I'd been blaming a small leak on the washing machine door seal). The pipe has now been properly capped, but we're left with a soaking wet floor - it's ceramic tiles laid on top of concrete over a loose scree, over a plastic membrane, from what I can see down the hole.

Things are complicated by it being over the top of a blocked-in cellar - this was done before we bought the house, so over 20 years ago, and we have no idea how it was filled or capped. Up until now, it's not been an issue, but the water from the leaking pipe will have also been running down into this old cellar. The house is over 150 years old, and there's no way into the cellar.

I'm seeing this as two issues: 1) the cellar space, and whether to even try to deal with any water that's in there, and 2)the kitchen floor, and how to dry that out. All I can think to do is to lift some of the tiles and let it dry out, though I have no idea how long that'd take. It's a tiny house, so there's not a lot of floor space anyway, and tiptoeing around a hole in the floor isn't going to be easy! I'm not even sure who I need to speak to about this - it's not exactly a damp-proof issue, as there appears to be a damp proof membrane (plastic) under the floor, and I can't see into the cellar to see how bad things might be in there.

Any thoughts? I'm at something of a loss, and not a little panicky about this!

 

[HERTS P&D]

Things are complicated by it being over the top of a blocked-in cellar - this was done before we bought the house, so over 20 years ago, and we have no idea how it was filled or capped.

Blocked in cellar, has it being filled in, where was the access before? Time is now to try and access the cellar and take it from there.

Post pictures.

Andy

 

[NippyNelly]

Holeinfloor

• NippyNelly
• 16 May 2021

shows newly capped old lead pipe, currrent mains water pipe, stopcock, and what is visisble in...

Hi Andy, I understand (from neighbours) that the entry was under the stairs, via stairs that would have gone down from inside the kitchen, I guess - there's not a lot of room (house footprint is only c. 4m x 7m). Cellar is a half cellar, about 4 foot square, and not tall enough to stand up in (if the neighbour's is anything to go by - in a terrace, and pretty much mirror images of each other). I don't know if it's been filled in - none of the current neighbours know. The entry was sealed and the floor tiled over before I bought the place, so I've never known. Didn't even know there was a cellar until one of the neighbours asked me if I used it! The only pics I have are of the hole in the floor where the lead pipe is - not sure what they're going to tell anyone, but happy to post if they really might help.

 

[HERTS P&D]

Ok, do you have a water meter? if so you can check it to make sure there are no other leaks.

Now the leak is fixed I would leave it 3-4 weeks and see if there are any signs of the damp coming up or if the water has just soaked into the cellar/ground.

Andy

 

[NippyNelly]

No, no water meter - actually don't know where the external stopcock is, as the one on the street closed off the neighbour's water, and the supply to the leaking old lead pipe, but not to the domestic water here. It's yet another riddle - these old houses! I kinda feel like there's not a lot I can do about the cellar itself, but I'm concerned about how wet the loose gravelly material is under the tiled floor - the grout between the tiles is really dark where it's wettest, so pretty much all the kitchen floor is indicating a lot of water under there still. I was thinking I'd need to lift at least some of the tiles, to help it all dry out - I also thought about drilling holes in the grout, to let in a bit of air, but there's a risk of going through the plastic membrane doing that Other than the hole where the pipework is, there's no ventilation to the floor. Do you think it'll dry out okay, or do I need to make more access for air?

 

[jacko555]

Get/rent some large dehumidifiers and run for a few weeks, until the humidity of the room decreases to something sane?

Also, isnt this an insurance job?

 

[NippyNelly]

Hi Jacko555 - I had enough trouble getting the insurers to cover the water leak, as there was some confusion over who it would come under (home emergency, or buildings insurance). I was going to give them a call in the morning to see what they say.

 

[JohnD]

your floor is tiled, is it concrete? if so the cellar is likely to have been filled in. Depending on the DPM, water may be absorbed into the walls.

look outside for any signs of airbricks, or holes drilled under the doorstep. If there are any, sniff them and feel if there is any air movement

lift floorboards in adjacent rooms, see if the void is damp. If so, improve ventilation by clearing airbricks and leaving a board open at the furthest point.

It's possible to improve ventilation with a fan ducted to the outside.

Do your kitchen units have plastic legs? take off the plinths to dry out the space. If you have chipboard in contact with a damp floor, it is likely to be badly damaged.

Open the doors and windows, and run the extractor fan at all other times.

 

[NippyNelly]

Hi JohnD - the floor is ceramic tiles laid onto what looks to me like a concrete layer, under which there is a layer of loose material. I can't see from the hole what this is all sitting on top of - the void there around the pipes shows the inner face of the external wall stones, and some rubble, but it's smack bang up against the side of the house, and I can't say if that's going to be typical of the rest of the cellar.

I'm guessing that the cellar HAS been filled in - these cottages are so small, any storage space would be valuable, so I can only think it was already damp. Two of the other cottages in this row had theirs filled in because they were damp. There's no airbricks into the cellar void; there are 2 into the underfloor void under the lounge, which has a wooden floor.

There was a damp prrof course injected all round about 20 years ago (just before I bought it), and there's a double thickness plastic sheet underlying the concrete, gravel and tiles of the kitchen floor. Kitchen units were tailormade by a chippy friend, as all the walls and floors were lacking straight lines or level surfaces, so at least I won't have weetabix chipboard (been there, done that, never want to have to deal with it again)

I've already pushed out what I can of the boards underneath, so get as much air around as possible, but it's the wet grout that's bothering me, as it suggests that that's moisture wicking up from under the tiles, most probably from the gravelly substrate. Sorry, don't know the right terms for all this stuff! If I can figure out the extent of the cellar, then I think an airbrick (or a fan, as you suggest) is a good idea, but this is an old stone cottage with 18" stone walls, so I really don't want to be drilling holes until I am at least half sure of where I#m drilling into.

It seems like people are saying to just leave it, and let it dry on its own.... which would be a lot less troublesome than trying to life some tiles to help it dry out.

 

[JohnD]

is it stone blocks, random rubble... or a stone face filled with rubble?

we don't have it in my area, but the only one I'd want to core out is the stone blocks.

I fear that may not be what you have.

A local builder, or a neighbour who's made alterations, will know.

Chemical injections not likely to work.

If the floor filling includes builders rubble, usually with plaster as well as brick, old mortar, and scrap wood, it may swell or subside when wet. Plaster is not good mixed in cement. You'll know if your tiled floor starts cracking and going uneven. sorry.

 

[NippyNelly]

Hi JohnD, from what I have seen, the walls are stone faced both inside and out, with a rubble core. They're thick but not very robust, if that makes sense - I agree that it's probably not what anyone would want to be cutting a hole in. They were farmworkers' cottages, so not high-end build. The stone is a very sandy limestone (we're on coal measures), so it erodes pretty badly. I'll canvas the other neighbours around and about to see if anyone has a better idea.

The loose layer seems to be mostly rounded gravel - the fine part of the matrix is very sandy. I haven't seen anything other than stone or concrete so fingers crossed no plaster, though of course I have no idea what would've happened to the original wooden floor. The current floor's been down about 10 years; the old floor tiles were taken up (they really were pretty ghastly) first as there wasn't the clearance to just tile over the top of them. I don't recall seeing any warping or cracking when that was done, so maybe it was okay.

It's kinda fascinating, really - I'd love to just dig everything up and figure it all out

 

[mattylad]

TBH it's probably not worth the effort digging it out.
Unless it's a very large room and your able to tank it well, then it is not likely to be usable for much.

 

[foxhole]

All you can do is wait , hot air fans will speed the drying process but could take months before everywhere’s dry.
I had a small leak from gutter which soaked wall and took over 9months before all signs disappeared.
These are available to buy or hire.
https://www.ebay.co.uk/itm/15196160...6&customid=aiwq_EMIAAAA9F6Tt-4RaLJQbW0BAAAAAA

 

[NippyNelly]

mattylad - yeah, that's pretty much the conclusion I've come to. It's only a half cellar at best, and next door's is only about 5 foot high, so it's a tiny space for the effort.... plus you've got to wonder why they blocked it in in the first place. It's the resulting damp I'm most concerned about - the last thing I need is even more mouldy walls!

foxhole - thanks for the link, will look into that. I've got a dehumidifier running at the moment, but the weather's so shocking at the moment, I think it's mostly just drying the rain rather than any part of the leak

 

[Deleted member 174758]

A lot of stone built terraces in my part of the world have a small "keeping cellar" or coal cellar beneath the kitchen. They are invariably damp, but it didn't really matter much if all you were storing in there was coal! Maybe that's why it was infilled - too small and damp to be used for much To be honest the type of liquid DPM applied to these houses can break down over time causing water to wick up the walls. Our cellar dried out after I scarcified the cellar walls and tanked them. The floor I sealed with epoxy paint in the summer when the water table is lower and the cellar drier

BTW on this street all our stop cocks are in the cellars. From my days fitting kitchens, though, I'd say most of them are under the sink on the back wall