Mesh backed "setts". - Conflicting advice from the trade.

[matthewt]

I have 170 square metres of driveway that needs to be dug out, levelled and prepared for the fitting of basalt setts. The setts are 100mm wide by 100mm, 150mm & 200mm long and 30mm thick. They are mounted onto a mesh backing sheet with a 7mm joint gap and come in interlocking sheets of 400mm x 600mm. These are on their way from China and cannot be changed. I have had conflicting advice as to how they should be laid. The original advice that I had from a company that no longer exists was that the driveway should be dug out, install a sub base of 150mm of type one or lean concrete, bedding 50mm sand and cement (four parts sharp sand one part OPC), then lay the setts with a bonding brige of SBR cement slurry. Then the joints should be finished with Rompox Drain or equivalent product to produce a driveway that will withstand the traffic and last for many years to come.
This method looks fine to me although I have had conflicting advice regarding the use of the bonding bridge (is it necessary) and the Rompox Drain type product, with some contractors suggesting that a more traditional approach would be better and considerably cheaper. Should the setts be bedded into the screed as it is laid or should the entire driveway be done, allowed to harden and then laid on the slurry?
My experience is that people generally recommend what they know and as such it is difficult to get an objective view. I am sure that many of the people using this forum have experiece of these products and hope very much that someone can give me a good steer on this.
Thank you in anticipation of your response.

[lutonlagerlout]

i would lay them onto a prepared screeded bed,but still plastic
as they are on sheets i wouldn't have thought any need for SBR??
i refer cement pointing on a drive but romex and gftk and instarmac all make good products
cheers LLL

[matthewt]

Thanks for the response, but I'm not clear on what you mean.
When you say "prepared screed" and "but still plastic". Could you explain please?

[lutonlagerlout]

lay and compact your subase to levels
lay 50 mm of screed 5:1 grit sand cement, screed this off then lay your mats directly onto it while it is still plastic,I.E. has not gone hard
then point ASAP
LLL

[matthewt]

Many thanks for the explanation. Sorry to sound an idiot but it's not an expression I've ever heard before.

[lutonlagerlout]

it sounded dumb first time i heard it
colloquially plastic is green
LLL

[cookiewales]

hi best practice to use a bond bridge cement slurry dont screed out to much because you cant stand on them clean of any splasses of slurry straight away romex is good for pointing these are not for the diy man even i would shy away from them but there on there way any help needed shout away :;): ???

[matthewt]

Thanks for the considered response Cookie. I appreciate that this isn't a DIY job, that's my next issue, finding someone in Bristol comfortable working with these products and capable of producing a fantastic finished result. The guy that talked me into these stones did so on the basis that they were considerably easier to lay than regular setts and that it would reduce the installation labour costs dramatically.

[ilovesettsonmondays]

cant you turn the ship back round to china.
i wouldnt want to lay them .bond bridge s lurry will suck the screed to the sett in theory. i would definately use it on what your laying .

[matthewt]

Ok guys, at the risk of derision from you all, from a layman's perspective, I would have imagined that these mesh backed setts would be easier and require less skill to lay than the traditional single sett alternative. Obviously I'm wrong about this but can someone tell me why?

[lutonlagerlout]

because most setts are 100mm plus deep so a good 50mm of the sett is bedded down into the bedding material

your matts are effectively going to lay on top
I would put PVA in the mix but that bond bridge is a messy job with slabs never mind these
what is the mesh made of they are linked on?
cheers LLL

[matthewt]

LLL, the mesh is polyproylene and is bonded firmly to the setts. SBR is specifically recommended over PVA, not sure why but PVA is NOT recommended. Could the slurry be applied to the screed and the setts be laid immediately on top? I would imagine that applying it to the mesh back would be near impossible without making an unholy mess.
I found this paragraph on the main Paving Expert website,
"The setts are cut, dressed and mounted onto a strong polypropylene mesh backing, so that, when it comes to laying, all that needs be done is to prepare a level bed, drop the mesh setts into place, consolidate with a plate compactor and joint them! It really couldn't be easier!"

[lutonlagerlout]

sorry daydreaming there sbr is weatherproof ,pva is not
I would lay them as detailed in your post
sbr bond bridges are only really necessary on free edges and steps IMHO
LLL

[matthewt]

I've just looked at it again and in fairness it looks like it might be a sponsored area for Rock Unique as it is a product that they promote and sell.
http://www.pavingexpert.com/stonpv01.htm

[ilovesettsonmondays]

going by what it says there .just lay them like you would block paving .except the kiln dried sand bit .would you use A mat too