standing water under 1930s semi

[diybeany]

Hi, is this normal to have 6inch+ standing water under the wooden floors when it has rained? (30s house & ash foundations I think) and is it okay to leave it as is? The water table is pretty high in our area and the garden often flooded before installation of a dirty water pump.. Next door have concreted theirs but it is very expensive and we could not afford that. I could install the same type of pump in a digout under one of the rooms but that would be awkward. It's been like this for as long as I can remember so my preference is to leave it as is if it isn't something that absolutely NEEDS fixing. thanks.
btw there used to be a musty smell but since we laid visquine?? under the laminate the smell is gone and no longer an issue.

 

[bobasd]

are you on a hillside or slope?
do you have plenty of all around the house air bricks for good through ventilation under the floor?
through ventilation means from the front elevation to the rear elevation.

what are "ash foundations"?
is the house built on made-up ground?

 

[Ian H]

How’s about dye testing your rainwater drains?

 

[diybeany]

are you on a hillside or slope?
do you have plenty of all around the house air bricks for good through ventilation under the floor?
through ventilation means from the front elevation to the rear elevation.

what are "ash foundations"?
is the house built on made-up ground?

yes all the houses in the road are built on the slope of a small hill. there are 2 vents on each of the 3 walls. I've always been told it's called ash foundation. My understanding is that the walls are sunk into the ground without concrete foundations and then bacfilled is cinder'sand'ash. etc. Basically it's compressed gritty/powdery matterial. Maybe it's the stuff they call fly-ash or flu-ash I don't know. But I'm told it was a very common foundation type for affordable houses around the time.

 

[diybeany]

How’s about dye testing your rainwater drains?

hmm? not sure. How would that work? afaik there is only one drain manhole at the front. There are also only 2 rainwater drains. Also I'm pretty sure the water is not coming from the drains but from the general water table. we had blocked drains once which smelled awful but the smell was not the same under the house which leads me to believe that the they weren't connected but I may be wrong. Many of the other houses have had similar issues but over time most have had concrete foundations poured to above the water table. Also it's rumored that the houses were built on or close to a stream

 

[bobasd]

thanks for your quick reply - hope i can finish this post, i'm waiting outside to get access to a void property.

its probably fly ash blocks that were used on a concrete strip footing.
thats actually irrelevant to your issues - ground water will be rising up more than penetrating the foundations.

concreting the over site often works for a while - but its best done in conjunction with a sump pit and pump - and you will be pumping out gravity driven ground water coming down the slope.
but even with concrete and pump ground water will often find and force a way through.

given you've got good through ventilation to help with under floor condensation issues then maybe its best to leave alone, and inspect the joists and flooring now and again for any signs of rot.
apparently the woodwork has survived for eighty odd years so far?

 

[Harry Bloomfield]

I would suggest that your neighbours concreting efforts have probably made your own problem even worse.

If you are on a slope, rather than at the bottom of a slope, might it not be possible to make use of gravity? Might it be possible to install a pipe from under your floor, out through a wall and to drain to a lower ground level?

 

[Ian H]

hmm? not sure. How would that work?

Put dye in your gutters or rainwater gully’s and simulate heavy rain with a hose. See if it shows under the house.

If it doesn’t then Harry’s suggestion of a drain in there is a good one.

 

[Leofric]

My understanding is that the walls are sunk into the ground without concrete foundations and then bacfilled is cinder'sand'ash. etc. Basically it's compressed gritty/powdery matterial. Maybe it's the stuff they call fly-ash or flu-ash I don't know. But I'm told it was a very common foundation type for affordable houses around the time.

gritty/powdery material as foundations under walls doesn't sound good.
As far as a solution to the water I would agree with above advice on drain and make sure it discharges well away from the foundations

 

[diybeany]

Thanks guys. This has given me a lot of food for thought. I'm leaning towards either the leave alone or sump pump approaches especially as I've had good experience with a sump pump in the garden. Its a semi and therefore even though build on a hill the actual siting for the houses is stepped with no real high/low within the individual propery and deliberately creating a connection into the existing drains doesnt sound like something I'd want to do. Like bobasd said the woodwork has been good for 80years. We did have one rotten floor area but that was due to a longterm leak from a washing machine. The damage didnt seem to have sread further than a couple of meters. (but woodworm was present there and could have spread I guess even though treated).

thanks for all your advice

 

[John D v2.0]

I'm no expert but even pumping out might cause an issue, if the water is seeping out gradually it won't disturb any ground, but if it's all going to the middle and being pumped away it could also be pumping away silt and clay. Usually happens from leaks, but could happen, maybe the pros can advise. So be careful of that.

 

[diybeany]

I'm no expert but even pumping out might cause an issue, if the water is seeping out gradually it won't disturb any ground, but if it's all going to the middle and being pumped away it could also be pumping away silt and clay. Usually happens from leaks, but could happen, maybe the pros can advise. So be careful of that.

yeh thanks for the head's up. Definitely dont want it eroding near any walls. In the Garden I put the pump inside a large bucket and mostly silt does not pass then. I would look to do something similar. TBH though I really like the idea of leaving it be and dealing with anything more serious if/when it crops up! I am a bit lazy that way

 

[Harry Bloomfield]

In the Garden I put the pump inside a large bucket and mostly silt does not pass then.

That would be reasonably effective, spreading the suction over a wider area of water. The problem with a sump pump, apart from the ongoing power cost, is how large a difference there is between starting and stopping height wise. They tend to draw the silt in towards the end of the run. A bucket, the larger the better, will make a lot of difference.