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Posted: Sun Feb 19, 2006 10:38 pm
by fritz
Firstly just to say great site !
I'm in the process of redoing a driveway and a contractor has suggested a 75mm coating of SMA (stone mastic asphalt).This would be laid on top of the existing tarmac driveway which has been crushed and compacted to appx 100mm deep.The initial 25m of the driveway is quite steep.Any advice would be greatly appreciated.
Cheers
Posted: Mon Feb 20, 2006 7:27 pm
by bobbi o
s.m.a is used as a thin (30mm) wearing course ,used on major roads,never seen it on a driveway.wouldnt look good.
better with a 60mm single layer depth of 6mm bitmac if the base is solid,otherwise 40mm depth of 20mm bitmac and 30mm of 6mm bitmac or for the best job-a wearing course of asphalt with 10mm white limestone chips rolled in
Posted: Tue Feb 21, 2006 9:39 pm
by Tony McC
I've seen SMA used on driveways and I'm not impressed. If there's plenty of room for a paver machine, and a more commercial-looking finish is acceptable, I suppose it might be OK, but it's not t my taste.
I'd also be concerned about laying it as a single 75mm course. I could understand a 50mm regulating course of DBM and then 25mm od SMA, but 75mm single layer is not something I could possibly recommend.
I still think the best value-for-money, all-round decent surface for a bitmac driveway is 50mm of 20mm base/binder and 25mm of a 6mm dense hardstone surface course.
However, regarding Bobi O's comments - white limestone chippings? Pur-leeze!! Leave that nonsense for the tinkers! :p
Posted: Thu Jan 29, 2009 3:57 pm
by Warden
Thanks again for the site and for the quick response you gave on a different thread.
Relevant to this thread, I've had 2 good quotes for resurfacing a drive. The cheaper is offering one 60mm layer of SMA. The existing drive is well establish, with hard-packed stone, although it has a number of pot-holes. (Drive is straight and level, 32m long x 3.2m wide.) The more expensive quote is offering 60mm of 20mm dense binder course with 30mm of 10mm close graded surface course hardstone.
You say SMA doesn't look nice, but have you got any photos to compare black SMA finish with black tarmac finish?
More importantly, do you think a single layer of SMA will give good service in this situation?
Thanks, Warden.
Posted: Thu Jan 29, 2009 8:00 pm
by bobbi o
generally SMA is used for commercial applications not domestic.i would only use a 6mm wearing course or an asphalt for a driveway.best to speak to the contractors and go and see jobs on the ground using the different grades before you decide.
Posted: Fri Jan 30, 2009 4:48 pm
by Dave_L
I beg to differ! I'd say 80% of our domestic driveway surfacing works are with a 6mm hardstone SMA macadam - purely from a durability and strength point of view.
I find the 6mm surface courses a little too prone to softening up in hot weather which then become scuffed etc
SMA has a slightly more open appearance, but if it is rolled and compacted correctly it is not an ugly material, far from it! My driveway is a 6mm SMA and features on this very website 
Whoever is quoting 60mm of SMA is a fool, both from a practical point and from a waste of good material!
Posted: Fri Jan 30, 2009 4:53 pm
by Dave_L
Warden wrote:I've had 2 good quotes for resurfacing a drive. The existing drive is well establish, with hard-packed stone, although it has a number of pot-holes. (Drive is straight and level, 32m long x 3.2m wide.)
So your driveway is a stoned-up surface at the moment?
Prior to any surfacing it would require grading back with an excavator bucket and any holes and voids filled - then suitably compacted to the correct formation level for tarmac.
For a residential driveway, I would specify a 20mm binder course at an average thickness of 50mm and a surface course of either 25mm (in a 6mm aggregate size) or 30mm (in a 10mm aggregate size)
Is your driveway straight running? Any turning areas? Any turning areas I would probably specify an SMA surface course.
Posted: Fri Jan 30, 2009 5:23 pm
by Dave_L
6mm hardstone SMA in red, my driveway, in fact!
Posted: Fri Jan 30, 2009 9:13 pm
by Warden
Thanks for the photo. Looks good to me. This is a rural area and within a few months it'll be covered in mud and grime anyway. Then it'll tone in with the tarmac surface it will be joined to. :;):
The real question is ... will a single layer of the stuff be tough enough to stand up to my neighbours' 4x4s and the occasional oil tanker, not to mention the sludge tanker?
Posted: Fri Jan 30, 2009 9:19 pm
by Dave_L
One coat magicoat being asked to deal with 4x4's, oil tankers and the shit-sucker?
I wouldn't advise it.
Posted: Thu Feb 12, 2009 9:24 pm
by colordrives
I 2nd Dave_L on this, we have used 6mm SMA for years on driveways where there is a chance cars will be turning on the spot, if we don't we get the customer ringing the following summer moaning cuss the power steering is twisting the tarmac up. I do agree it does not look quite as "closed" but hey I'd rather it lasted twice as long...
Posted: Fri Feb 13, 2009 7:02 pm
by Dave_L
Yep, as soon as there is any chance of vehicles turning in a tight area, we use SMA - it's far, far more resistant to scuffing from turning vehicles.
Not as easy to lay but quite easy to roll up and achieve a decent finish aslong as the material is up to temperature.
Once the surface has weathered in and filled up with fines etc, it looks absolutely fine.