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Posted: Tue Aug 04, 2009 1:29 pm
by Chomper90
I like the look of indian sandstone (probably raj green) and the price is attractive, but just wondered whether it is suitable for use in a small but sloping driveway? Is it durable enough? Do the flags get too slippery for a sloping driveway?
If so, are these problems solved if indian sandstone cobbles are used instead of flags?
I am aware that the quality of Indian sandstone can vary enormously, so would be checking this and would use thickness of 40mm.
The drive would be approx 40m2 and will get fairly light use - one mid size car. The slope is approx 1 in 5. Any help much appreciated.
Posted: Tue Aug 04, 2009 2:12 pm
by Tony McC
And where will you get Indian sandstone flags at 40mm or more?
I'm not overly fond of using the thin imported flagstones on a driveway, but, as long as they are laid on a concrete bed with full support, they tend to be just about OK.
Posted: Tue Aug 04, 2009 3:00 pm
by Chomper90
Thanks for the response and advice - yes, you are right that most of the indian sandstone flags are less than 40mm - but I have seen indian sandstone 'cobbles' that are 40mm. I was particularly worried about whether the flags would be too slippery for a sloping driveway and whether the cobbles might provide a bit more grip?
Posted: Tue Aug 04, 2009 8:29 pm
by Rich H
The 'cobbles' are called setts. Grip will not be a problem with either, provided the paving has adequate drainage. I wouldn't lay Indian sandstone slabs for a driveway, just because you only need one dodgy slab to bugger a reputation.
I'd certainly use the setts, though. Bit of a balls-aching job to lay (as it all needs to be jointed) but would be a great looking drive. Consider GftK or Romex jointing compounds. Both have versions which are suitable for vehicle traffic and, while much more expensive in material cost than jointing with mortar, the time saved would be immense.
Posted: Fri Aug 07, 2009 8:14 am
by danstan
Hi
Check out 'Old Rectory Cobbles' by Global Stone.
35-50mm or Limestone 40mm Calibrated. Gorgeous product!
We stock York Green and Modak Rose.
Dan
Posted: Fri Aug 07, 2009 5:25 pm
by lutonlagerlout
i know you have an interest in flogging them dan,but IME of laying theold rectory walling they were more like 35-70 mm
nice looking stuff per se,but dunno where they get the 35-50 routine from 
LLL
variations in thickness
Posted: Fri Aug 07, 2009 8:54 pm
by Tony McC
So: the Indian sandstone flags might be too slippery but Indian sandstone setts probably won't.
I'm interested to know why you think smaller units of the very same material would behave differently in regard to its surface slipperiness. Is this just a 'non-expert' perception or do you have some rationale for believing size would make a difference?
Posted: Sat Aug 08, 2009 8:11 am
by danstan
Old Rectory Cobbles - not walling.. totally different product.. i agree the walling is a massive variation but i'm talking about the cobbles - 35-50mm
http://www.globalstonepaving.co.uk/detail_old_rectory_cobbles.html
Dan
Posted: Mon Aug 10, 2009 8:47 am
by Chomper90
Tony re: slippery flags vs cobbles?
It is a 'non expert' opinion, I (perhaps naively) reasoned that as cobbles were smaller, they would have more 'edges' per m2 so would provide more grip, but I have no evidence or experience to back this up!
Posted: Mon Aug 10, 2009 9:15 am
by Tony McC
I see. I wondered if it might be summat like that.
In theory, more joints create a more uneven surface and therefore create a coarser macro-texture, but the problem with most setts is that a typical "foot" would span two or three at a time, while a tyre would be even less, so the macro-texture is just a bit too 'macro' to make a significant difference.
There was a paper published last year (or the year before) which looked at the effect of element size and joint width on slip resistance value (SRV) but can I find this bloody paper now that I'd like to reference it? Can I buggery! 
Posted: Tue Aug 11, 2009 2:02 pm
by TheVictorianCobbleCo
I've done hundreds, if not thousands of square metres of cobble paving using simulated concrete setts, they WILL be less slippery than slabs, the smaller irregular surface logic is quite correct. Obviously in winter one might need a grit. The slabs will crack if not FULLY supported, and theres an art to making sure they are properly sat down. Expansion and contraction variations in the concrete base/slabs could cause movement/cracking, and the grinding of tyres (power assisted ) is a negative on slabs, and slabs don't like point loads. If he is still around Phillip Sinclair of ScottKerb could make you sandstone cobbles, I can't seem to raise him, his website was on this forum. Good luck.
Posted: Tue Aug 11, 2009 10:21 pm
by cookiewales
chomper you could use a granite set which has far more going for it there are plenty of good new ones out there or even reclaimed setts grit sand on concrete cobbles not a good idea takes the surface of
Posted: Wed Aug 12, 2009 7:39 am
by TheVictorianCobbleCo
Granite setts will be lovely , variations in each units depth make laying a bit more difficult. "cookiewales - question - concrete cobbles not a good idea takes the surface of --what?
Posted: Wed Aug 12, 2009 8:09 am
by cookiewales
grit salt in winter is not recomended on concrete products that are made ie wet mix on vibrating tables as to there smooth surface there are some on the market with exposed agragate surface but price wise they can be dearer than granite on the laying side sand and cement and pointing more expensive but done right is more than a life time job there are still some lovely roads and market squares with more than 100 years plus wear out there them old boys knew there game