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Posted: Sun Oct 02, 2005 8:37 am
by bevly
I've just discovered this site and looking forward to accessing it as my husband and I attempt to lay our first block paved drive!!! 
We are looking to cover aprox, 118 sq mtrs. Ideally, we want to use natural stone, but granite setts are WAY beyond our means, but we came across this product last year and are wondering if anyone else has used it/can offer advice on it's suitability.
Aparently, Porphyry is a very hard volcanic stone which naturally cleaves along a bedding plane(?). The result is a very even texture to the split face. It is extremely durable with extremely low porosity and a very high figure for its crushing strength.
We're interested in using the Porphyry cobbles, which come mounted onto a mesh back for ease of handling/laying. The 'square' is 500 x 500mm, made up of 25 individual cobbles which are 100 x 100 x 40mm thick.
We've noticed that these are only 40mm thick, whereas the manufactured pavers are 50-60mm thick. Would they be suitable for a drive, with an adequate sub-base of course?!
Has anyone else come across these, or used them?
Look forward to getting any reply's.
bevly
Posted: Sun Oct 02, 2005 5:48 pm
by Tony McC
These mesh-backed products are becoming increasingly popular, Bevly, and I negotiated a sponsorship deal with a supplier just a couple of weeks back, so there will be a page of highly detailed laying advice and tips added to the site later this year.
Porphyry is a vastly under-rated stone. It is eminently suitable for residential paving projects, for both patio and driveway use as it's a relatively hard stone with attractive colouring, good slip values and low absorption.
The only thing you need to consider for your project is just how you would joint these mats of individual setts. The jointing will make or break the project, believe me.
Incidentally, I was looking at some tumbled basalt setts last week. These come in a just a shade more expensive than tumbled concrete blocks, but are much cheaper than granite setts and far, far easier to lay. Given the choice between mesh-backed porphyry and the tumbled basalt, I think I'd go for the latter, as long as the price was right. How much are you being asked for the porpyhry?
Posted: Mon Oct 03, 2005 4:07 pm
by bevly
Hi Tony McC,
Thanks for the quick reply.
The price I've been quoted for the Porphyry is £35 sq mtr plus VAT.
We were thinking of using a mesh backed product because if we're doing it ourselves, we thought it would be easier to lay! (but then what do I know!!).
When will you be posting up information on jointing, as we could do with all the advice we can get before attempting this project. In the meantime, I'll look into those setts you mentioned.
Posted: Mon Oct 03, 2005 5:00 pm
by bevly
Further to my last reply, I've just had a 'quick' read-up on jointing and have a couple of questions/queries I'd appreciate your advice on.
The sample Porphyry mat I have has the cobbles stuck onto the mesh aprox. 10mm - 25mm apart. From what I've read, this product is regarded as a 'flexible' product, and because of the gaps, would benefit from a pitch jointing.
However, as these 'cobbles' are only 40mm aprox. thick, I can't see that there's enough depth to allow for the gravel prior to pouring the pitch. How would you 'joint' them?
Are the tumbled Basalt setts available from most builders merchants? I've skimmed through the merchant list but can't seem to locate them.
Posted: Tue Oct 04, 2005 11:52 pm
by Tony McC
35 quid for the porphyry seems reasonable, but I'll check it for you as I'm sure I've seen them for under 30 quid.
The "How to Lay...." page is at least 6 weeks away as the 'review' meeting to look at the content and finalise the images is not scheduled until the start of November - that's part of the problem when working with sponsors: I have to fit in with their schedules instead of doing what I want when I want.
I've not used pitch jointing with this type of product and it's not something i would suggest without checking it out for myself first. My first thoughts are that the scale of the setts is such that getting the molten pitch to flow within the joints could be a problem. However, I'm also concerned that pitch at 180C could be warm enough to melt that mesh backing and I'm not sure what effect that might have.
For driveway use, I'd probably consider one of the better polymeric jointing compounds (NOT GeoFix, which is shite), and this is one of the topics being examined for the forthcoming page(s). Early testing suggets that one product in particular seems to perform well, but the test panel has only been in place for a couple of weeks, so I want to reserve judgement until it's had at least 6 weeks of daily traffic.
Regarding the tumbled basalt setts, as far as I know they are an exclusive product from Rock Unique in Sevenoaks. I've seen them loose in the crates, I've seen a test panel that's been in place for over 3 months, and last week I got to see a 200 sq m driveway laid with them and they are abso-bloody-lutely stunning. When I get back to my desk tomorrow I'll upload a photie or two.
They are a bit more expensive, but the jointing is straightforward and they are laid is exactly the same way as regular (ie concrete) block paving.