A previous owner has laid a concrete path too high along the side of my house (built in 1939). It almost touches the Damp Proof Course (from 25 to 5mm away!), for several metres, so damp is now rising along the inside wall's plaster.
I've been told I need to cut a long, 6 inch wide trench against the wall and fill it with gravel so surface water drains away from the brickwork. I was planning to cut the concrete with a large angle-grinder, to get a straight line.
Is an angle-grinder the best way to go?
Will I be able to break-up and remove the resultant concrete 'strip' with hammer & chisel, or will I need more power?
Just how deep a trench should I did, and what's the ideal gravel to fill it with?
Is the concrete strip likely to have bonded to the brick course and cause damage to it when pulled away?
I know that there are some very elaborate diagrams on this website for new installations. I'm more seeking a best course of action now to remedy someone else's poor design.
Cutting a channel in concrete to keep damp away fr
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Tony McC
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Use a cut-off saw or floor saw rather than a nangle grinder and have a look at this page on the main website, which work perfectly well without gravel infill (which is a bit of nonsense, to be brutally honest!)
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Dave_L
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Interesting work-around page there Tony! Like it 
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Roy22
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Tony,
Thanks for the reply. Do you mean the ‘dry area arrangement’ diagram? From your comment about gravel, I take it you mean that all that matters is restoring 150mm of ‘fresh air’ around the bricks below DPC level, and that gravel doesn’t help?
I understand the 150mm depth, that’s a couple of bricks worth. But does the channel need to be 200mm wide, rather than the often quoted 150mm? I’m just thinking about the postman etc putting his foot down it, or tripping over the raised edging kerb stone if I fit one as shown?
Thanks for the reply. Do you mean the ‘dry area arrangement’ diagram? From your comment about gravel, I take it you mean that all that matters is restoring 150mm of ‘fresh air’ around the bricks below DPC level, and that gravel doesn’t help?
I understand the 150mm depth, that’s a couple of bricks worth. But does the channel need to be 200mm wide, rather than the often quoted 150mm? I’m just thinking about the postman etc putting his foot down it, or tripping over the raised edging kerb stone if I fit one as shown?
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Tony McC
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There's a sort of hierarchy for these problems: ideally, you'd have the paving 150mm below, but if that's not poss, a Dry Area arrangement is next best, and then, if that's not practical, gravel infill is better than nowt.
For the channel itself, the depth is more important than the width. As long as you are at least 150mm below DPC, the width can be whatever you like. In the diagrams on the main website, I show a 200mm wide channel because that happensd to be the width/length of a standard block paver, but if you wanted 150mm, or even 100mm, I wouldn't object. However, there's a width below which access for maintenance becomes awkward if not impossible. For me, owt less than 100mm just operates as a litter trap and makes cleaning hard work. 150mm I can live with, but I find 200mm to be ideal as a minimum and the width I've used on my own house. If I had the space available, I might have gone for 300 or 450mm wide, but as this is a narrow access driveway to the garages at the back of the houses, I needed to keep the channel width to a workable minimum, which, for me, was 200mm.
For the channel itself, the depth is more important than the width. As long as you are at least 150mm below DPC, the width can be whatever you like. In the diagrams on the main website, I show a 200mm wide channel because that happensd to be the width/length of a standard block paver, but if you wanted 150mm, or even 100mm, I wouldn't object. However, there's a width below which access for maintenance becomes awkward if not impossible. For me, owt less than 100mm just operates as a litter trap and makes cleaning hard work. 150mm I can live with, but I find 200mm to be ideal as a minimum and the width I've used on my own house. If I had the space available, I might have gone for 300 or 450mm wide, but as this is a narrow access driveway to the garages at the back of the houses, I needed to keep the channel width to a workable minimum, which, for me, was 200mm.
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