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Bricks and Brass • View topic - French Drain or "Dry Area"

French Drain or "Dry Area"

Forum for discussing period houses.

French Drain or "Dry Area"

Postby belgrade123 » Thu Jan 04, 2007 4:40 pm

We have a Victorian Mid Terrace property that has a patio in the back garden that butts up against the external walls including an alley-type-way that runs back along the side of the kitchen. Where this part of the patio meets the main back wall of the house there is very little drainage and the patio bricks meet the bottom of the airbricks. We have a lot of moss on the patio in this area, I am assuming this is a good sign of dampness.

This has lead to damp occurring in the kitchen and the back wall in the living room.

We want to re-do the kitchen but I want to get rid of the damp first.

I have been told that a French Drain would be best to remove the damp and stop any moisture getting at the external walls. Obviously there is a lot of work involved in a French Drain and they can cause increased damp rather then solving the problem.

I have also been told that a "Dry Area" may work as well.

Can anybody offer some advice on which method would be better?

Thanks

Patrick
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Tradeoff

Postby Simon TL » Thu Jan 04, 2007 8:55 pm

Hi Patrick

It's one of those tradeoff things - there are 'very likely to work but costly in time/money' solutions and the 'may work but cheap' solutions!

If a full French drain is too much, then at least taking out a slice of the paving - say 9-12 inches, digging the foundation out to say 9-12 inches deep and filling it with pea shingle is a fair compromise.

A weaker solution would be taking the same slice out of the paving, removing any rubble and filling with soil as needed, and planting some leafy plants - these will consume some water and also deflect rainfall.

If the slabs slope towards the house - so that water drains into the new trench - then all these options may fail! You could add a 'rib' to the slabs to stop this. It would be a good idea to go out in some heavy rain and watch what happens!

Do be aware that even with an effective solution it will take 8 months or so for the wall to dry out.

Hope that helps.
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Re: French Drain or "Dry Area"

Postby Mandy-Looo » Mon Feb 01, 2010 9:56 pm

Hi. I'm just searching through old posts so I don't ask a question which has been asked before and lo and behold!

I've been lurking a little on here since the summer when had our offer accepted on a late- Victorian property which we knew had a very similar damp problem to the one described above. We knew the previous owners had put in a chemical DPC into the wall last May, then plastered straight over it (I doubt with breathable plaster) and of course it's all now peeling off again. After having a read on here at the time, I knew they hadn't done the right thing to solve the problem. Now it's time for us to take th more proper action.

It seems quite daunting to dig up concrete slabs, so where would I go to get someone to dig a drain like this? Do I just need a builder and to tell them what to do?

We also have what looks like a problem with a drain in the area where the damp looks the worst. The drain looks damaged and may be blocked. What should we do abou this? The drainpipes look ok.
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Re: French Drain or "Dry Area"

Postby tim smedley » Thu Feb 04, 2010 10:16 pm

Mandy

Firstly, before you start anything I would work on the theory that when built the damp was not a problem - it is a recent issue as far as the life of the house is concerned. Thus before doing anything else I would sort this blocked drain. There are very few damp proof methods that will make up for a blocked drain flooding the area. It is hard to advise but a hand in a rubber glove clears far more probelms that you might think! Alternatively drain rods can be rented cheaply or there are also dynorod type organisations. I would also scrape away the moss as this can act like a wick and pull the water from the patio onto the wall.

Sorting this may well fix the problem, if not reduce it enough to the point where the repair work carried out can cope and all of them are cheaper than installing new systems. Remember that in the present weather it might take weeks to see an improvement.

On the face of it this sounds like it would solve the problem but after that I would start by imagining the layout of the building and grounds as it would have when first built. As far as you can tell is thepatio a recent addition? If so, does it fall away from the house - watch the rain as it falls where does the water run to and can you make more of it flow away from the house? Can you remove some of the patio to create a small gap between it and the wall? Again, easier to pull up and relay a patio properly than dig drains - probably considerably cheaper too.

If you do want a drain then it is not a highly skilled job, but it will involve a lot of digging! A general builder should be able to help and the website http://www.kwintessential.co.uk/article ... Drain/2440
has a number of excellent articles that will point you in the right direction.
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Re: French Drain or "Dry Area"

Postby Mandy-Looo » Fri Feb 05, 2010 10:12 am

Thanks Tim.

The patio is most definitely a more recent addition (i.e. not an original feature) and runs right up to the air bricks. I'd be fairly certain that water is entering through the air bricks a a result of this.

We are getting the drain looked at, this weekend hopefully. We don't think it is blocked; we think it is damaged and there is at least superficial damage to the mouth of the drain which may be diverting water to the foundations.

I think our problem is more properly problems; there is water going from the downpipes and not not being caught by the drain and there is water getting in through the air bricks. The patio is going to have to be changed.
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Re: French Drain or "Dry Area"

Postby tim smedley » Wed Mar 31, 2010 8:58 pm

How did you get on?
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Re: French Drain or "Dry Area"

Postby Mandy-Looo » Mon Apr 05, 2010 8:55 am

We're still looking for someone to do the work!

We've got one quote in, but want to get another before going forward. This is for repairing the damage to the drain entrance and digging out the patio around the back wall.
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