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Posted: Sun Nov 13, 2005 7:14 pm
by colinhainsworth
Hi Great site. I have had a good look but can't find the answer! I am looking at changing my driveway (mixture of pea shingle and mud!) I would like to use weathered flint. I am being advised that the slope (approx 1.5m in 26m) is too large a slope for gravel - without rejects being concreted and bonded in to "trap" the gravel. In fact the contractor has quoted £12K for block paving (160 sq m) and £11K for the gravel option - but he is really pushing the block. My question is the slope really that bad for a standard gravel construction as per your site? Would a 3m strip of block bordering the road be wise?
Thanks
Posted: Mon Nov 14, 2005 1:11 pm
by Tony McC
1.5 metres over a 26m run is equivalent to roughly 1 in 18, which is just a bit much for an unbound gravel. If a client was insisting on using gravel on such a gradient, I'd push them to use a self-binding gravel, and warn them that there will be some migration, but not as much as there would be with a loose gravel. I'm not sure how well a 'weathered flint' would hold up as we don't get that type of material in the north, but as it is essentially limestone-based, it might be suitable.
I'm concerned that on a project of this scale, the contractor reckons there;s only a grand difference between using blocks and using gravel. I'm guessing that he really doesn't want you to have gravel!
If you do opt for a gravel, some form of 'trap' at the base of the slope will be essential, otherwise you risk losing your driveway to the public carriageway. A 3m wide strip of block paving would provide a platform from which the escaping gravel could be swept and returned to the top of the slope, but I'd consider installing such a strip somewhat like a 'speed hump' so that it works as more of a barrier to the gravel. If you used, say, a half-battered kerb laid on its back at the interface between blocks and gravel, that would help keep more of the gravel on the driveway and off the blockwork.