builder lined my french drain completely with concrete!


Postby stickybubble » Wed Sep 15, 2010 4:34 am

I'm really worried about this and need some feedback and advice.

I have a very old stone house that is at risk of (brief) flooding and suffered badly from damp when I moved in. Water also came up through the floor when the water table was very high. My former partner said the walls needed to breathe and dug out the concrete that abutted the walls to put in a french drain, and also put a drain under the house that takes water out to the trench. This seemed to work and solved a lot of the damp.

Now he is gone and I got a builder to finish various work, including the drain. He dug out a lot more concrete and I thought 'looks good'. Then he said he wanted to line the sides with concrete. This seemed half-way sensible as the sides could be unstable etc, and the mortar in the wall was getting worn away at the bottom. He used a lot of shuttering and this took longer than I thought, and then when the shuttering came off and I had a look I saw he had lined the WHOLE trench with concrete, sloping down to where I wanted to put a pump (no natural drainage slope away from the house for when there is a LOT of water, or the river floods). I should explain the trench fills the space behind a retaining wall, which keeps the worst of the flood away from the house, and I needed this finished so I could put the new front steps in.

Now I'm getting really worried. He was talking about making the concrete on the house wall even higher 'in case it floods higher'. We spent ages smashing through it! I feel like such a fool for not being more on the case while this was happening. I DID try to explain several times about the french drain and the concrete was a last-minute addition - I was actually just expecting a thin layer over the bottom of the wall that could be painted with bitumen.

What do I do now? Get him to take it out? He won't be happy. What could his reasoning be? Am I being silly? I feel like maybe leaving it for a few years and seeing if it really does cause damp in the house again, but changing it later will mean re-doing the whole front, steps and all.
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Postby stoneyboy » Wed Sep 15, 2010 5:38 pm

stickybubble,
Without seeing the drain it is difficult to say whether the right action has been taken.
If the purpose of the drain is to catch water running over the surface of the surrounding land and to stop it getting under the building then what has been done may be right.
If the purpose of the drain is to catch sub-surface water from the land surrounding the building then lining the whole drain is probably wrong.
I don't think you have any option but to play the waiting game and see what happens.
end
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Postby stickybubble » Sat Sep 18, 2010 4:32 pm

stoneyboy wrote:I don't think you have any option but to play the waiting game and see what happens.


I decided that too, and took the bull by the horns and spoke to the builder at length. Part of the problem was that until I took the panelling off the inside wall at the w/end the amount of water coming up wasn't at all obvious. He has come up with a suggestion of an open trench along the adjacent (problem) wall, where we know there is a small spring and a soggy area, that drains into the existing solid trench with the pump.

I did feel bad about it but he took it on the chin, and I said if we leave it all alone for now and finish other stuff first that should allow plenty of time to see if there is a problem.

I think the real big problem here is that we have both flooding from on top and rising water from below at times. He also thinks the concrete should be impermeable and not wick water into the walls, which is the complete opposite of what my ex told me. I'm not a builder so I don't know who is right.
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Postby stoneyboy » Tue Sep 21, 2010 9:34 pm

stickybubble,
"He also thinks the concrete should be impermeable " Depends on the strength of the concrete mix and whether a waterproofing additive was used.
Wait and see.
end
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Postby TheDoctor4 » Fri Oct 25, 2013 1:21 pm

For readers looking for related advice please see our drainage DIY how to projects pages which are targeted at the most common drains-related questions we get here at DIY Doctor.

We also have a specific project page for anybody wishing to install a French drain.
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Location: Somerset in the UK in Shepton mallet


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