ash132

puddles of water under suspended floor

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I’m in the process of renovating my house. I’ve had a rear full length extensions and small front single storey extension to square off the house from the front – it was previously L shaped.

In between the two extensions, which have solid concrete floor, I have the existing living room with a suspended floor – I Have had the floorboards up for the last 3 weeks as I’ve been cleaning out the void and insulating between the joists. About 3-4 days ago I noticed some puddles of water on the ground after the heavy rain and then again today. I went to check on the house this morning and the ground looked OK, damp but no puddles. I then came back in the evening and noticed some large puddles of water. I bought a wet vacuum and reckon 7-8 of the 14ltr buckets of water drained out and it was still bad.

The ground would literally fill up with water within a few mins of draining it out.

I live in a clay area which is prone to water logging. I’ve had land drainage put into the garden and the amount of water running through to the man hole is quite surprising, even when there’s no rain, there’s a steady stream.

The front of the house is a bit exposed at the moment - its just ground with no slab or anything and rain water has been forming large puddles where the ground has been taking the weight of the skips.

My question is it possible for rain water which is puddling on the drive to make its way under a concrete floor and through to a suspended floor? If not then what is the likely source of the water?

Is it possible for that much water to come down a chimney or a faulty drain water pipe?

I’m looking to install land drainage on the front but is it worthwhile putting some kind of drainage under the suspended floor before I seal it back up?

Any advice would be appreciated.

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I would say without a doubt you have high ground water.

 

How have you ensured the air bricks to the existing suspended floor are still ventilated?

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@ash132 as @ProDave suggests, first area I would check is air bricks.

 

Have external levels been raised/is water running off downpipes etc?

 

For damp and suspended floors, I would check out a few of these videos.

 

 

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10 hours ago, ProDave said:

I would say without a doubt you have high ground water.

 

How have you ensured the air bricks to the existing suspended floor are still ventilated?

 

Yes, there's air bricks to the back and front connected to ventilation ducts which run through to the suspended floor. I’ve also knocked out a brick as shown in the pic from under the floor which leads to a cubby hole under the stairs. I plan to stick a floor grill on the other side to allow more air in.

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is the drive higher than the underfloor space that is flooding?

how much height difference between air bricks and outside ground level --can you see the DPC in the walls outside above the ground level --It must be  clear of  touching any ground outside 

must be an old house if that under floor area was not blinded with concrete when built 

If enough depth to play with then maybe you should drop in a dpc and concrete over that underfloor area  keeping that level below the dpc in house wall.

6" is normal height for dpc from outside ground level

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56 minutes ago, ash132 said:

 

Yes, there's air bricks to the back and front connected to ventilation ducts which run through to the suspended floor. I’ve also knocked out a brick as shown in the pic from under the floor which leads to a cubby hole under the stairs. I plan to stick a floor grill on the other side to allow more air in.

 

air bricks should only vent the under floor area -and be sealed off from  area above floor 

is this house solid walls or 2 layers of brick with a cavity  in between them 

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13 hours ago, scottishjohn said:

is the drive higher than the underfloor space that is flooding?

how much height difference between air bricks and outside ground level --can you see the DPC in the walls outside above the ground level --It must be  clear of  touching any ground outside 

must be an old house if that under floor area was not blinded with concrete when built 

If enough depth to play with then maybe you should drop in a dpc and concrete over that underfloor area  keeping that level below the dpc in house wall.

6" is normal height for dpc from outside ground level

 

Yes, I had the drive cleared and some MOT put down before the extension work started.
There's probably 2-3 courses of brick between the air brick and ground level

Yep, 1930's - still had a back boiler when I bought it!

 

I have thought about it and it would be as a last resort. Now that the house is sealed I’m not keen on having the mess of concrete/ screed barrowed in through the front door.

 

The house is two skinned with cavity.

I had a builder around today who could not work out where the water was coming in from. Said he'd never known water to come through a solid concrete floor like I’ve got at the front. Though, there’s a small gap to the side of the front where the drain pipe from the roof is and he reckons the water might be forcing its way through this gap between the foundation and neighbours house through to the suspended floor?!

My idea is now is to scrape off a layer of the soil from the front and lay down some DPM, lap it into a land drainage channel and back fill. Hopefully the bulk of any heavy rain then just drains off into the mains...

BC have suggested internally, I could use a layer of roof membrane under the joists – allow air up, but stop and water coming through.

I’ll see how this works first.

 

 

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friend of mine had same sort of problem 

he fitted a slot drain,plastic type with removable lids , all round the outside of house and that cured it 

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13 minutes ago, scottishjohn said:

he fitted a slot drain,plastic type with removable lids , all round the outside of house and that cured it 

My living room has a suspended floor below ground level and I was getting water ingress as the house faces directly into the prevailing wind and rain.... huge amounts of water just had nowhere to go quick enough. I extended the base of the house out with an apron and fitted a big old cast gutter pipe and it’s been working really well. Every location will be different but this worked for me, the rusty streak is the air vent.    

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I have built on a site with clay soil and a variable / high water table. All fine and dry during ground works but towards completion it rained lots. After the rain, even a hole dug for a tree would fill with water as you dug. Ground water made its way into foul drains via not perfect seals in plastic inspection chamber risers.

 

If you can get some drainage under the floor, leading to an external drain, it would be worthwhile. Make sure there is no way the flow could be reversed!

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Dig a hole outside to the same depth as the soil under your suspended floor. Wait for 48 hours of dry weather, drain both the experimental hole and the underfloor void then compare the height of water at both locations after 10 hours. If the same then that is your ground water table and consider your house did not sink for 80 years in these conditions.

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