Water under the floorboards!

Steve J · 20 Jun 2007

Help!

We've had a crazy amount of rain in Harrogate recently (like in the rest of the UK) and we've had the smell of damp in our lounge for a few days. We have a small letterbox sized air vent in our lounge floor (possibly for the gas fire) so I stuck my arm down there with a camera...

Yep, there's a shallow (about 2" deep at the point where I can see the floor directly) pool under the house.

With more rain on the way I don't really want to just wait it out.

Could the water table have gotten so high with the rain?

Every room on the ground floor has really well laid laminate flooring posh stuff too that actually looks good) so taking that up is a last resort. We've only been in the house 6 months.

Advice?

Thanks,
Steve.

JohnD · 20 Jun 2007

Is the house built on a concrete raft?

Can you get access under the floor e.g. under the stairs?

is the ground flat round the house, and is there e.g. a flowerbed where you could dig a pit next to it?

how do you feel about crawling in confined spaces?

p.s. have a browse of
//www.diynot.com/search/forum.php?search=sump+and+pump&action=Search

the reason I asked about a concrete raft, is that if you pump out and the house is built on soil, the water brings with it partcles from the soil, thus leaving a hole that your house can subside into.

Steve J · 20 Jun 2007

The ground appears to be hardcore rather than concrete upon trying to get a stick into it. It's not just soil anyway.

Nope - even in the understairs cupboard they did a great job of the laminate! The kitchen is the only floor we'd be willing to sacrifice in order to get a better look as that's just fake wood tiles.

There's a flower bed at the front of the house where there's just some heather growing. I assume you're thinking that we can dig down below where we believe the water level to be to see if the whole fills with water to confirm the level of the water table?

Thanks,
Steve.

JohnD · 20 Jun 2007

I think you need a sump, and to pump it out. But (see my p.s. above) the pit needs to be lined with porous concrete blocks or no-fines concrete, otherwise the ground will be washed into the hole and be pumped away, and your house will fall down. If there is any fall in the ground, you could lead a pipe away from your sump to take the water away from the house (you are not allowed to put groundwater into drains). You could even lead it into a garden pond large enough to accommodate the volume of water in wet weather.

It would be worth consulting a local builder or surveyor, who will be familiar with local conditions and presumably have come across the problem before.

If your house was built on concrete, you could have a pump under the floor in a small depression or at the lowest point, or construct a concrete sump under there. But it looks like you may need to drain the water level round the house instead.

p.s. have a good look round the gutters and downpipes for anything that might be delivering water onto the ground beside the house.

Steve J · 20 Jun 2007

Thanks John.

For the record though crawling about in confined spaces is not really something I'd look forward to!

I'll see if I can get into the soil near the house tonight to see if the water is just soaking in naturally.

There is a drainpipe that comes down from our roof and goes into the ground directly (rather than a drain). I don't know if this goes into the drainage system or just into the ground. A recent addition to the water this takes happened last year when next door built a conservatory. Now that drain takes the water from their conservatory roof as well.

Unfortunately I can't get to that pipe as it runs down between our extension and their conservatory and there's less than a foot of space between them.

Steve.

PS. More photos of the problem here http://www.bombedout.com/temporary/underthefloor.rar

DIWHY · 20 Jun 2007

Hi Steve,
Given that you have you only just smelt the damp even though you have lived here for some time it could well be the recent neighbour downpipe addition, either a bad connection or some overflow?

Your timbers and brickwork do look in remarkably good, dry, rot free condition which would suggest a recent water ingress, and not long term standing water providing this is an older house.

I have just just replaced a full rotten floor and joists in a 50 year old detached bungalow and some joker had already tried it once during its life, he actually gaffer taped the floorboard gaps to seal in the smell.

We have land drained it all around, checked all drain gulleys and relaid flags. And its now got more air vents than brick and its cured.

Add vents for good unrestricted airflow and watch what your surface water is doing i.e patio runoff etc.

Hope you sort it before it affects your timbers.

Steve J · 21 Jun 2007

Update:

Yorks Water are coming out to check their pipes and drainage. They implied over the phone that they reckon it's the rain that's to blame but they'll come and check anyway.

Oh, and next door have the same problem. They've been in their house only 2 months longer than we have. They couldn't find access under their boards but a bamboo cane into a small knot-hole came up with an inch of damp at the end.

Next door-but-one don't have standing water but they do have signs of damp under their boards - it looks likes it's been wet under there but has since drained. They've lived there for 4 years and never had (or noticed) a problem.

None of the neighbours seemed unduly worried but granted none of them have the smell coming up from an airvent in their lounge floor.

It's not the downpipe that I mentioned as it turns out that is piped into the sewer on my neighbours side (they checked it when the conservatory was built).

If this is a one-off because of abnormally heavy rain what are the risks in doing nothing?

HandyHands · 21 Jun 2007

Are any of your external air bricks at ground level ?. I had this with my parents house last year. When they bought it, the previous owner had concreted up to the walls, and the air bricks were at the same level as the concrete. When it rained, water would pool around a couple of the air bricks and run into them. Resolved by cutting away the concrete and backfilling with pea shingle. I also installed andled covers over a few of the exposed air bricks - the ones that took a fair hammering from the weather. Air can still circulate, but rain cannot get into them.

honda · 9 Jan 2008

bit late but would like to re-open this topic. my house and those surrounding have had water under floors since they were built in 1934 due to clay soil and high water table. i had to completely replace one floor , as it was rotten, in 1972 when i bought the house. at the same time i knocked a hole in the outside wall and laid a drain from there to some waste land at the bottom of my garden which fortunately is 10ft lower. since then i'm left with a 8x6 pool about 2" deep under the hallway in a dip in the oversight concrete. i would like to get rid of this with a sump and submersible but ( i think)the house is built on a raft .would this make any difference if i dug a sump and wouldn't the concrete be pretty thick?

JohnD · 9 Jan 2008

fill in the dip with concrete and lay to a slight fall to the drain

if you build a sump in clay you will suck out the mud as well as the water. The mud is the clay on which your house stands. When the hole gets big enough the house will fall into it

honda · 9 Jan 2008

thanks johnd. think i'll forget the sump in that case!

shana · 18 Jan 2008

we just bought a house 2 weeks ago and the Surveyor missed out the clues to inform us that we have about 2-3 inches of water under the floorboards in the ground floor of our house esp under the Kitchen and Bathroom. How have you resolved this? I have had 2 builder/plumbers who have given me different quotes for remedy. Both indicate water has entered the property from the Garden due to poor drainage and guttering. I have been told the remedy would be to repave the garden with cement/ guttering and to have damp proof course here. Timber would have to be replaced and the Kitchen/ bathroom would need to dry out with dehumidifier to prevent wet/dry rot. Help!!!! Also - has my Surveyor been negligent for not spotting this? What has this cost you?

JerryM · 20 Jan 2008

I’ve had this problem myself. The house has a through lounge and Canadian redwood flooring which I wanted to strip back. It’s probably one of the hardest things I’ve sorted. The big difficulty being the space to work in.

There is no easy solution and if not sorted the timbers will rot. I think the extra rain in the last few years (and no dry summers) has compounded what has been an unnoticed liveable problem for years in a quite a few houses.

The cause for mine was the high water table but as pointed out in the other posts it could be rainwater from problems in the garden and surrounding paths, patios and the like.

The pump solution is proven and probably most practicable if the depth under the floorboards is low (difficult to crawl, ie typ 400mm). My only hesitation is that it’s a wet solution which is ok if it’s checked that the ventilation sufficiently limits the level of moisture in the joists.

I had typ 700mm depth. I initially put down 2” concrete floor on a DPM. I then tanked the walls and ended up putting a tanked mortar chamfer to bridge the floor dpm and walls. Finally as a precaution I put in extra air vents. The floor is now totally dry and joist moisture levels staying below 20%.

I think with hindsight (and this is difficult as the floor does look stunning) I would have replaced the floor with concrete.

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Water under the floorboards!

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