Advice on water/flooding

Hi
Am after some advice/help. Hopefully I'm in the right place, if not please accept my apologies.
I have bought a house that was built in the mid 1930s and am in the middle of renovating it. It also backs onto a graveyard.
When looking under the floor boards in the front room and kitchen I've noticed when it rains that there is water appearing. However it is about 2.5ft down and doesn't come above the damp proofing and it disappears when the rain stops. I've been tearing my hair out trying to find out what it is but haven't succeeded.
However when discussing this I've been told that this design of house was what was common in the 1930s and that all that is happening is the natural "water table" is rising when raining, the level is rising under the house and that as long as the water does not go over the damp proofing or breach the flooring then it is fine and nothing to worry about. They also said that the graveyard makes this worse as it acts as a natural sponge.
Does this sound feasible? Am I worrying about nothing? Anyone with similar experience?
Thanks
Neil
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In an earlier contribution to this discussion,

Sounds odd! How deep does the water get under the floor - and how much does it have to rain to achieve that?
It sounds to me as if your guttering/downpipes are discharging into the under-floor space rather than into a proper drain to carry the water away. In some cases soakaways are used - but they're usually *outside* the house!
--
Cheers,
Roger
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It sounds quite feasible.. what you need to do is find out how high it can get. If it can get too high you may need to install a pump or find some way to lower the water table. You really need an expert not some "help" from the internet where no one can actually see what is happening.
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My house has something similar.
When I first noticed a smell, there was coincidentally a broken sewer at the other end of the street, and a suspicion that there might be a blockage in that. Once the sewer was fixed the smell in my house got much less bad, but didn't disappear. I explored under the floor and found standing water on the solum.
Experiments showed that the sewer was probably irrelevant, as (a) when I ran a shower in the room above, water ran down the walls below the shower-tray. I fixed that, then in doing further testing of the shower noticed that (b) whenever a shower had been running for a few minutes, there were visibly moving water currents in the standing water. I found that water was spilling into the cellar through the outside wall.
A local plumber came and pressure-jetted the drains (expensive, and I'm not convinced that this didn't make the situation worse). The jetting did show water coming up from underground suggesting a leak in a drain (as I'd thought in the first place) but he'd assured me that jetting would solve it. I couldn't see how...
He nodded knowledgably about how it'd be a broken something-or-other, and offered to fix it, but by then I wasn't interested. I asked for a quote for a fix, just to see how much brass neck he had... In due course I lifted the slabs outside and dug down to find a broken clay pipe (fed by downpipes from roof gutters). Someone much cheaper than the local plumber fixed it in due course, and water stopped swilling back into the house. In the course of looking for the problems the weak layer of bitumen on the solum was pierced, probably because some of the earth underneath had been washed out. There was standing water on the solum.
After the drain was fixed, the spare water was pumped out. But more arrived. After a while, I'd got the 'standard' water level down to about 6" below the solum (so in total about 3 feet below DPC). It's hard to say what the outside ground-level is, because the house is on sloping ground, and at the back (where the problem is) there's a sort of patio area abutting the house. Still, I think the water level is maybe 18" below ground level.
When there's rain, parts of my garden and that of the neighbours' gardens get waterlogged (and always have done as far as I'm concerned). I'm tending to think that although we're on the highest ground around, the soil has a high clay content and holds water, which takes longer time to run off than you might expect. Also the gullies in the streets don't have drains in them - water is expected to run along the gullies (slowly going down hill) and then run into a more major road and presumably eventually into storm drains.

Is there any point if nature provides a continuous top-up? In my case after the standing water had been pumped out I lowered the pump below the solum. After a while, it kept pace with continuous slowly arriving new water. The water always seemed pretty clear, making me think it is rainwater or from a spring.

Where does one find such an expert?
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Jeremy C B Nicoll - my opinions are my own.

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How high is the land outside with respect to the base of your cellar? If higher how far away from your house does the land become lower. The fact it floods only during rain does suggest it's a storm drainage problem. How quickly after rain does it go away (inches/hour).
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Neil wrote:

Perfectly feasible. I was talking to someone with 6" of water in their cellar the other day, and he can only remember it happening 3 or 4 times in the 20 years he's lived there.
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In an earlier contribution to this discussion,

Except, if I read the OP correctly, he seems to be saying that this happens every time it rains - not just once every few years.
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Cheers,
Roger
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We were somewhere around Barstow, on the edge of the desert, when the
something like:

When I was putting in my septic tank I noticed the water table here was about three feet under surface level - at least, on that day. So, it sounds perfectly feasible that what you've been told is true.
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Dave
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Neil wrote:

Its water.

Oh yes, although in my case it was causing a problem as
(a)it was only about 9 " down and
(b) there wasn't much of a damp proof course (injected brick plintsh with mostly rotten sole plates above), and
(c) worst of all, brick chimneys that were uninjectable going straight into it).
Its probably OK in your case, but if you have wooden floors, you need excessive underfloor ventilation, and that makes the rooms cold, if no insulation is provided. That can mean rats/mice and the like can get in too.
Also, if there is any air route into the house, you can get stagnant whiffs, and its a nice mosquito breeding ground in wet summers.
I would say you have three possible approaches.
1/. Do nothing.
2/. Dig a trench round the house as close in as you can, and put in a perforated pipe in pea shingle, and run the water off to a low point. If you are on a slope, this will lower the local water table considerably.
3/. Go the whole hog: take the floors up, and shove down loads of hardcore and rubble and MOT, to raise the actual floor level above 'flood' level, and then cast a concrete floor below damp. DPM it, insulate it, screed it and put in underfloor heating for your new heat pump :-)
Or you could simply back fill it with porous material - that at least stops there being surface water, which is what stinks and causes mosquitoes, and then seal and insulate the floors above it.
,

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Neil expressed precisely :

I would guess that if it rises rapidly and falls quite rapidly, that it is a leak from a surface water drain. Ground water levels do move up and down, but generally not quickly.
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Regards,
Harry (M1BYT) (L)
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Harry Bloomfield wrote:

Come and live here for a week then.
There are more than one sort of 'water table'.
Underground aquifers are one thing, but what is happening to runoff after a big storm is quite another: here it goes underground, appears above ground, catches in hollows and so on.
If the soil is relatively impermeable, and here its clay - you can have a puddle on the surface and then relatively dry two feet down, and you then need to go down another ten feet to get to permanently soggy clay.
My general solution has been to infill the sorts areas with gravel or hardcore or MOT and then soil over that..the water just runs an inch or two underneath, in the permeable layer I have stuffed in. Where it does little harm.
In clay, you cannot really talk about a water table as such, since the rate of percolation is so low as to make it a very localised affair. OTOH what else do you all it?

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I raised part of my garden because the local water table used to come above ground. However, it usually lasted weeks, if not months. Water coming and going when it rains suggests you need better land drainage. If the land slopes, the drains need to be on the uphill side to protect your house.
However, water that stays well below the DPC is not a problem. I use to live in a place near a tidal river, where the under floor area would be wet on any spring high tide and that had been standing since 1882. The phones also played up at high tide until BT came around and remade the connections in the manhole in the road outside.
Colin Bignell
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Firstly, thanks everyone for replying. Didn't expect so many responses.
With regards to drainage my main storm drain which runs at the back of the house has been flushed and CCTV'd and shows nothing. It is strange as the water appears almost in the centre of the house, between kitchen and living room and that is why I'm struggling to understand how it is happening.
I do have another drain on my property which I'm guessing is the sewer connection at the side of the house. I don't have any guttering leading into this drain but I've noticed the front half of next doors guttering does, so I will get that checked.
When I bought the house it had been blocked paved along the front, above the damp proofing. I took away the edging and put that coloured shingle around it, which is below the damp proofing. The guttering at the front of the house just runs into the shingle which isn't ideal, yet I cannot see how it could get from there to the middle of the property without seeing it run along to there. I've got quite a few floorboards up in the living room and the front and sides seem dry. The guttering at the back of the house goes into the storm drain there.
If it rains then it gets quite a bit of water in, though I must stress it is still a couple of feet below the floorboards. It stops raining and, depending how much water is there, disappears in a few hours to a day.
Part of the problem is I'm not exactly sure who to talk to about it hence the posting on here. If the other drain is okay then I'm stumped. Not really a plumbing issue, not sure if the average builder would know exactly. Maybe a surveyor might be the best bet.
Thanks again to everyone.
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Ask your local councils building control officer if he has any advice.
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Neil wrote:

A lot depends on soil type: what are you on?

Thats pretty much the way mine used to happen.
One thought. Your underfloor has ti be vented somehow. If those vents - which are blow damp obviously have entrances that have been covered over by shingle..water will piss into them.
When I rebuilt the house I fitted perscope type vents that exit above ground, but inside the house are below the outer ground level.

Always the very bet bet. Ive had advice off here that ha saved me thousands, and exceeded anything I got elsewhere.
If the other drain is okay then I'm

I don't think we have fully explored this yet., Need to know soil type and a sketch of the layout and land falls if you can post it somewhere would be good.
Thinking is a lot cheaper than getting a man in, or digging up more floors etc.should be able to reduce the otions a bit at lest.

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Neil wrote:

No, thank you.
Since you posted this we've had a lovely dry week, one of the nicest of the year!
Andy
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I'd forget builders and surveyors for the moment because, if it's a water table issue, there's probably not a lot you can do about it.
Talk to neighbours. They are almost certainly affected as well
If you dig a 3 foot hole in the garden, you may well find it has a foot of water in the bottom, which would kind of prove the point.
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Neil wrote:

Which suggests to me that the sub-floor beneath your house is lower than the adjoining ground level.
Modern requirements for a timber joisted floor are that the sub-floor should be no lower than the adjoining ground level, or if on a sloping site, the sub-floor be laid to fall to part of the ground that is lower.
There are many 'traditional' building practices that we no longer regard as acceptable, such as draughty windows, cold rooms, poor plumbing, etc. Water beneath the floorboards is one of them. Putting a concrete oversite beneath the floor may do something about it; irrespective of that, make sure there is plenty of ventilation to the floor void to allow it to dry out.
--
Hugo Nebula
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