I have identfied a High Moor Gritstone sett that would like to use for my drive (8m x 5m) which would be complimented by the path to the front door in the same Gritstone flags.
My concern relates to the risk of spalling as the edges are not chamfered when butt jointed (3 - 5mm) as eloquently highlighted in your web site. Assuming it is laid professionally i.e. correct sub-base, and bedded in with sand & cement mix, what is the probability that spalling will occur? Also are Gritstone more or less likely to spall? Is there anything else I can do? The drive will only need to take a car.
Many thanks in advance!
Yorkstone setts & spalling risk
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84-1093879891
Who is supplying the setts? Are they "sawn 6-sides" or have they been tumbled?
With sawn setts that are not chamfered or tumbled, you need to ensure a 3-7mm joint between them, which, when filled with jointing sand, will act as a sort of cushion and prevent any spalling.
You mention laying on a sand & cement bed: if this is your chosen laying method, then you could use wider joints, say 9-15mm and point/grout them with a mortar and thereby eliminate the risk of spalling.
Gritstone, as a laminar sedimatary rock, will spall if units are knocked together. There's no figures that estimate incidence or likelihood of spalling, but is is common, especially with flexible construction methods, which is why tumbled setts are a much better choice for that type of construction.
With sawn setts that are not chamfered or tumbled, you need to ensure a 3-7mm joint between them, which, when filled with jointing sand, will act as a sort of cushion and prevent any spalling.
You mention laying on a sand & cement bed: if this is your chosen laying method, then you could use wider joints, say 9-15mm and point/grout them with a mortar and thereby eliminate the risk of spalling.
Gritstone, as a laminar sedimatary rock, will spall if units are knocked together. There's no figures that estimate incidence or likelihood of spalling, but is is common, especially with flexible construction methods, which is why tumbled setts are a much better choice for that type of construction.
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Andrew M
- Posts: 6
- Joined: Thu Jan 15, 2004 10:13 am
- Location: London, N21
Thanks Tony,
Yes they are sawn setts and the supplier is Natural Stone Sales Ltd, Derbyshire (do you know them?). I have seen this product on a commercial building near where I work & thought it looked good. Also I think it would suit my house & would be something different from the more popular tumbled setts (e.g. drivesett tegula) which incidentally I do think look fantastic. But sometimes its worth going the extra mile (& expense!) to create something different.
My preferred contractor uses the sand & cement bedding option. I will discuss with him your suggestion of the mortar grouting. I would prefer a smaller joint as possible but 7-9mm joint could be fine.
Failing that, I suppose I could always park the car on the road outside!!!
All the best.
Yes they are sawn setts and the supplier is Natural Stone Sales Ltd, Derbyshire (do you know them?). I have seen this product on a commercial building near where I work & thought it looked good. Also I think it would suit my house & would be something different from the more popular tumbled setts (e.g. drivesett tegula) which incidentally I do think look fantastic. But sometimes its worth going the extra mile (& expense!) to create something different.
My preferred contractor uses the sand & cement bedding option. I will discuss with him your suggestion of the mortar grouting. I would prefer a smaller joint as possible but 7-9mm joint could be fine.
Failing that, I suppose I could always park the car on the road outside!!!
All the best.