iMCaan

Water Seepage

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Hi

 

We are just in the process of building a house and are currently working on substructure.

 

I have found the location of the water seepage. It's right in the centre of the house. It's small amount of seepage but it builds up and we have to pump it out every couple of hours.

We have not had rain for a few days.  The site slopes from the road towards the back of the house. There are no drains on higher end (front of the house). The bay window trenches, on the higher end of the slope, are dry.

 

Any advise how this water seepage could be stopped?

 

 

Thanks

iMCaan

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Foundations below the water table are not uncommon, I had to pump mine out before pouring but i did back fill around  the outside with drainage stone to act as a French drain then extend it to a ditch nearby, my water table in winter is about 100mm below garden level 😱.

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How far below ground level are you there?

 

As @joe90 our foundation trenches filled up with ground water and had to be regularly pumped out.  Not an issue once you are out of the ground.

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Water goes where it can, so when that is all filled in it will not have that hole to fill.

 Is your floor going to be suspended or ground-bearing?

 

If on the ground, any water just stays under the dpm and there is no issue.

If suspended then a protected solum is a good idea.  More a Scottish detail but I would do it anywhere if it seemed wet.

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Thank you.

 

I reckon the water seepage location is about half a meter below block and beam floor.

French drains is a good idea (only idea so far :)). The water seepage is in the middle of the house so running French drains outside of the house would have to go trough trench blocks. Could this create issues later on?

 

Thanks

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12 minutes ago, iMCaan said:

Could this create issues later on?

Actually I remember now, I left a gap between a few trench blocks to stop water building up under the floor.

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58 minutes ago, saveasteading said:

If suspended then a protected solum is a good idea.  More a Scottish detail but I would do it anywhere if it seemed wet.

What is a “protected solum“ that’s new to me. I assume it is some form of sub-floor drainage arrangement? I would always recommend some drainage of sub-floor voids but haven’t seen any authoritative guidance on subject

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4 minutes ago, Gordo said:

“protected solum“ that’s new to me

My term I think.

The solum is the ground surface beneath the floor, whether sat upon or exposed.

 

In a suspended floor situation it involves a dpm under a rough concrete or stone covering to keep it in place, and the dampness is excluded.

Not sure whether it is in the English reg's.

No drainage.

Old timber floors tend to be in much better condition when there is this subfloor.

 

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20 minutes ago, saveasteading said:

My term I think.

The solum is the ground surface beneath the floor, whether sat upon or exposed.

 

In a suspended floor situation it involves a dpm under a rough concrete or stone covering to keep it in place, and the dampness is excluded.

Not sure whether it is in the English reg's.

No drainage.

Old timber floors tend to be in much better condition when there is this subfloor.

 

Yeah I agree on drainage to floor voids but never gave detailing much thought. I have experience of a few flooded/ponding sub-floors. Especially with the drive towards level access for wheelchairs raising GLs leaving void vulnerable to ponding water. Wouldn’t want to provide a route for vermin and like either or for ingress of ground water. Maybe a untapped gully connected to a BIGT above water line?

Edited by Gordo

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Hello @iMCaan

 

Concrete founds are fine under water and as others say seepage at this level is quite common.

 

If you are wanting to drain the site a bit I would avoid if possible placing the drains below the level of the top of the concrete found.

 

What can happen is that folk go mad and dig deep French drains near their founds. If in clay soil this can dry it out in the summer and your building could settle. If in sand the fine grains could get flushed out from under the founds.. and they settle. 

 

I've seen this on old stone built houses / steadings / shallow founded corbelled brick founds etc where folk put in a new drain deeper than the existing founds surrounded by pea gravel and a few years later cracks start appearing in the walls as they have dried out the ground under the founds that have happily sat there for decades.

 

Most of the time movement is caused by blocked drains and tree roots and that is what you read about on the internet. Thus when new building we don't think "the other way round"

 

 

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4 minutes ago, Gus Potter said:

What can happen is that folk go mad and dig deep French drains near their founds. If in clay soil this can dry it out in the summer and your building could settle. If in sand the fine grains could get flushed out from under the founds.. and they settle. 

 

Phew, I dodged a bullet without knowing it then! I did try to run a perforated pipe out from just below the top of our extensions footing trench to the rainwater drain but didn't have enough fall so took it off from directly on top of the concrete foundation instead. Glad you mentioned this.

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