3 May 2021
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United Kingdom
I have just purchased a terraced house. Built circa 1890. It's in a row of 24 houses built on a relatively steep hill. The houses are built in pairs. Each pair is lower than the pair before as they step down the hill. I'm near the bottom. I'm situated so that, looking at the house, the house to the right is higher than me, and the house to the left is on the same level. The higher house has a floor level at least 2 feet above mine.

I knew there was an issue with the floor before I bought. Yes I did have a survey. The floor near the right wall was springy and there was a smell of damp. The house had been empty for over a year.

So, I got the keys and was keen to find out what was going on. The ground floor was two rooms, knocked through in the 80s. The front room seemed worst affected. I took up the plastic laminate flooring to find all, I mean all of the floorboards soaking wet. Around the fireplace next to the wall they were non existent and what was there was infested with what I believe to be wharf borer larvae.

I could cope with that. I removed most of the floorboards in the room. The cavity underneath was full of detritus, rubble from the removed wall and silt. Lots of clay silt. It was really wet. There seemed to be 'flow marks' from the party wall, through a gap that had been knocked in the dwarf wall and through to the front door. Removing the boards at the front door revealed a drain pipe that leads out from the house, deep underground.

So, I've spent a week removing the detritus - literally tonnes of it, and I've been drying the room out, and dug a trench out the front to bring the exterior ground level down to install ventilation etc. All the good stuff.

It rained heavily last night, and most of the day. The more it rained, the more the ground in the house filled up with water. Most of it seemed to come from the wall, so it would be water flowing underneath my neighbours house. As the water level rose, it started to flow to the front door and down the mysterious drain hole. The sound of rushing water down there was tremendous.

I appear to have a house on a water course of some kind. It is also obvious that this flow is historic and has been known about. Recent work suggests someone has tried to stem the flow with expanding foam (!!) I'm at a total loss as what to do. My trusted builder is confounded as well. Advice ranges from adding french drains out front and channeling the water under the house to filling it with concrete (no, don't worry I won't).

The problem is confounded by the space under the floor being very shallow. The bottoms of the joists are only 4 or 5 inches from floor. I've dug down but I've found the strip brick foundation, and I'm wary of going any lower.

It's a wet mess. I'm at a loss as to what to do. Surveyor, groundwork specialist, water board, all three?

Thoughts and comments really appreciated,

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I attached two pictures. One of the fireplace, wall and water. You can see how it pools and flows out. The other is the drain at the front door.


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Well I would say your first point of call should be the water board.

I understand they test for the presence of summat to determine whether its sewer/treated water or not.

Obviously with what you've described, it sounds like run off, but best to get it checked.

2nd of all, you need to work out where its coming from. It could be an old storm drain that has broken/was never finished, and if you can determine this, you maybe able to get someone else to pay for it.

I would say you need to start looking for an expert to help on this one- it could be very expensive!
I’d be looking at doing loads of dye tests to the hg e higher properties rain water drains and to have the outlet near the door as the lowest point under your house.
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Yes, that's exactly how it sounds. I thought the same myself.
...Is replacing with a concrete floor really such a bad idea considering the situation?
...Is replacing with a concrete floor really such a bad idea considering the situation?
Theres a danger of driving the water up into the walls , the water has to go somewhere .Perhaps it may be worth looking into Foamed glass and limecrete with some perforated pipe taking the water out through that drain although in the instalation guide it says to consult an expert. If you ring and talk to them ,they are very helpfull or there may be other suppliers closer to you
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The good things are that you seem to have somewhere for the water to go, and if you're saying that you can see under the higher neighbours floor from below your floor then that party wall should be relatively easy to keep dry (I have a similar stepped terraced with solid floors where it's quite difficult to keep water out from the soil forming the neighbours floor which is about a foot higher than my floor).

If you can establish that it's groundwater and not a leak then I would (after investigating the drain - you can buy cheap boroscope type cameras for this) do as Ian H suggested, put in a dished concrete subfloor to collect and direct the water to the drain. You could consider a pipe directly from where the water comes through the wall to the drain (like a culvert) and put in a concrete floor over the top but I'd be wary of that in case it gets blocked. Fit a new well sealed suspended floor and loads of underfloor ventilation and tank the bottoms of the walls. You could also ask neighbours/local building control if this is a common local issue.
Whilst these are great suggestions, I would still look to work out where its coming from, as prevention is better than cure!
Just as a frame of reference, the house was built in the 1890's and is still standing. Therefore the problem must be manageable or the house would have fallen down long ago.

Sounds like there is a broken drain somewhere if the volume of water increases that fast.
Thanks for the continued advice. Both seem like very good ideas which I will follow up.
I'm convinced that it's rainwater and nothing else. As well as seeping from the walls it's rising from the floor on the left side of the fireplace so it must be where the water table is close to the surface on the hillside.
Good question. A strange arrangement of guttering. Mine flows from my house straight into next doors gutter before flowing down a down pipe to heavens knows where. It's like that all the way down the hill.
I would check your insurance and then get them involved, as it could be costly and they will do all the liaising with neighbours and relevant parties and anything legal that needs dealing with or putting in place.

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