adequate drainage
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pkarees
- Posts: 1
- Joined: Mon Nov 10, 2003 12:50 pm
We have recently had two areas of riven stone paving laid. They are both extend 7 m from the house. We have a fall of 30mm on one and 45mm on the other. We feel the fall is inadequate but the contractor says there are no British standards and the fall is OK. He also says that recommendations in books are for DIY purposes and not professsionals. Comments much appreciated.
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84-1093879891
There are no British Standards specifically for patios, but BS 7533 Code of practice for construction of pavements of precast concrete flags and natural stone slabs states:
"A minimum longitudinal fall of 1.25% and a minimum crossfall of 2.5% are recommended for carriageways using paving units as a channel. For other areas a 1% longitudinal fall and a 1.25% crossfall are recommended..."
A patio would be classed as an 'other area' and so a fall of 1% longitudinal would be the minimum accepteable.
Actually, as these are riven patio flags, which are a bugger (technical term) for holding surface water, a minimum fall of 1.7% would be better, and I'd prefer to see a fall of 2%
30mm over 7m is 1:233 or 0.04% and 45mm is 1:155 or 0.06%, neither or which are acceptable for any form of paving.
Ask your erudite contractor which "books" are to be used by professionals. I'll bet he can't name them! (this is a bit of a trick questions as the 'books' are actually BS publications and Spec for Highways Works, but just how far these standards can be applied to patios and driveways is a moot point!)
"A minimum longitudinal fall of 1.25% and a minimum crossfall of 2.5% are recommended for carriageways using paving units as a channel. For other areas a 1% longitudinal fall and a 1.25% crossfall are recommended..."
A patio would be classed as an 'other area' and so a fall of 1% longitudinal would be the minimum accepteable.
Actually, as these are riven patio flags, which are a bugger (technical term) for holding surface water, a minimum fall of 1.7% would be better, and I'd prefer to see a fall of 2%
30mm over 7m is 1:233 or 0.04% and 45mm is 1:155 or 0.06%, neither or which are acceptable for any form of paving.
Ask your erudite contractor which "books" are to be used by professionals. I'll bet he can't name them! (this is a bit of a trick questions as the 'books' are actually BS publications and Spec for Highways Works, but just how far these standards can be applied to patios and driveways is a moot point!)