Groundwater under floorboards - advice?

[eelsupinsideya]

We've recently discovered approx 2 inches of water under our suspended wooden floor, following the very heavy rain a few weeks ago. (Lived there only 15 months, 1930s detached).

We vax'd out most of it and it has all since disappated into the ground.

We've had a broken rainwater gully fixed, had the drains checked and the water supply checked, no other leaks. The ground slopes towards the house and we are a 'low' point of the street, so it seems to be a water table issue.

Chatting to the neighbours has revealed previous owners used to pump the water out (not disclosed to us when purchasing but thats another story and something we need to decide whether to pursue)

What sorts of things can we do to mitigate this? I've over googled as per normal and now don't know what the best courses of action are to take...

I've read about sump pumps - who could install these? We were about to install some lvt over the wooden floors but this would mean we couldn't monitor levels or access a pump.

We are planning to get the driveway and garden tarmaced/re- paved (currently very old cracked concrete) - obviously we now need to consider drainage carefully, but it is an opportunity to install some better drainage - what should we consider - french drains, land drains, soakaways? Who would we go to for advice, driveway companies, landscaping companies, drainage companies or groundwork companies?

Someone has also suggested a layer of gravel in the void to cover up to the level the water came up to - is this likely to help?

Any advice would be much appreciated, thank you.

Following and bumping for you.

Thank you

I would consider a grassed front garden as it will help absorb rainfall. Tarmac will be non-porous and the water will just run down towards your house if it is at the low point.

if you're on a slope, it would be preferable to build a drainage ditch or french drain uphill of the house, to catch the water, and lead it away, past the house, and/or to a soakaway. You are not allowed to put groundwater into a sewer.

Depending on the ground, a sump pump can cause a hole under the house, if the house is built on earth or clay, which turns to mud when wet, and the pump sucks it away.

Thanks haydnp I would prefer not to grass it, but was considering some well placed thirsty plants at the front and at the back which is currently all grass, no plants.

Thanks PigletJohn I was hoping you might answer! French drain round the front, got it. And the soil is clay so maybe a sump isn't a good idea. What are my alternatives though - just pump out as and when?

Any thoughts on the layer of gravel under the boards, presumably to soak/cover it up? The void is about a metre deep at the deepest point so its a way off coming through the floorboards but the electrics are under the house which worries me.

I've also noticed a road gully.in line with our house that often overflows in heavy rain and is suken, need to persuade the coucil to come and check it.

What experts do I need to consult? Is a general builder my best bet?

Thanks for reading!

I we have exactly the same problem - 1930s semi in a 'clay' area with a high watertable. All the houses round here are the same - the gardens can flood after just a day or two of heavy rain.

I was really alarmed first of all, but kind of figured it's been happening for 90 years! We had a damp proof specialist come round to look at some dodgy joists , and he didn't seem to be concerned about water coming in as it's common in this area (and it's unrelated to the damp joists). I was surprised, as huge alarm bells were ringing for me!

Some houses have sump pumps but we haven't, based on the points that pigletjohn mentions in their post.

Obviously, the reasons for your water might be different to ours. Do you have any damp? Perhaps get a damp / rot specialist to come in and survey first? It cost us just over £100.

I’m another one with a 1930’s semi on clay who gets water under the house when it rains. No issues with damp (lived here for over 10 years) just the way the houses are around here.

Yes, I forgot to mention that. No damp here either (apart from one joist). Moisture readings at floor level are normal.

I don't think adding gravel will help.

I had a related problem in that my house is lower than the street and my (quite large) tarmacked drive sloped towards my front door where there was a tiny drain leading to a old soakaway which just couldn’t cope in torrential rain. I used a surfacing contractor (i.e. someone who creates drives whether from tarmac or brick etc.). They dug up my drive, inserted a huge soakaway and then replaced the tarmac but inserted a long French drain a couple of feet away from the house. The tarmac between the house and the French drain slopes towards the drain so that water never reaches the house. This works perfectly.

Thanks all for your replies, I really appreciate it. Its reassuring to know other people have had the same without any issues - I know it must be really common and its probably under a lot of old houses without the owners even knowing - I'd just rather it wasn't mine!
I think french drains and a couple of soakaways are the answer then. Hopefully that will be enough.
No damp under the floors as far as I can tell, the space has had extra vents put in so has airflown through it so I think once the water dissapates it drys out ok. Will look at getting this checked. May have to go for carpet in the dining room now instead of the LVT I had wanted so we can peel it back and check under the floors periodically :-(

Thank you all again for your advice - any other advice/experiences welcome!

Put in a nice trapdoor. Preferably in a corner away from the door and traffic paths.

Do this www.greendriveway.com

That looks interesting, wonder how well it works on clay soil. Will add it to my list to investigate, thanks.

If the water is just high water table and you are worried about the humidity getting high under the floor then the gravel would help as there wouldn't be an exposed surface of water evaporating into the floor void.

I would also look at a green drive to allow water to be absorbed by the soil. You do, however, need to be aware of “heave” where excess water in Clay expands the clay. This then pushes the foundations upwards. I would get advice from civil or structural engineers about all possible solutions and difficulties you might encounter.

Thanks all

Hope you could help, I have exactly the same issue under my flooring and I only realised when having insulation. Have just recently purchased the property.
eelsupinsideya has the drains and soakaways resolved the problem?

@Ginand3

Hope you could help, I have exactly the same issue under my flooring and I only realised when having insulation. Have just recently purchased the property. eelsupinsideya has the drains and soakaways resolved the problem?

I strongly recommend you start a new thread, because the causes, and the remedies, of your problem may be different and the thread will be confusing.

When you do, include a floor plan, showing the positions of downpipes, gullies and manholes, and photographs of them. And the positions of your outdoor and indoor stopcocks, and any damp patches.

You're the fourth this week.