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Posted: Fri Aug 14, 2009 10:39 pm
by Richey
Hi all,
Today I saw a group of pavers laying a large block paving driveway, only they were cementing them in and it reminded me of my hard landscaping lecturer who said that more and more landscapers are doing this instead of using sharp sand. I never questioned him about it at the time but would like some feed back on it if anyone can tell me the for's and against's I would be very interested.
Cheers
Richey
Posted: Sat Aug 15, 2009 4:05 am
by Suggers
The collective noun for a group of pavers (sic) is....
Cement = dust
Mortar = dust + sand
Concrete = dust + sand + aggregate
Can't believe your hard-lanscaping lecturer said this - I reckon you fell asleep, and the next day, copied the notes from that pretty girl with the pony tail? 
Posted: Sat Aug 15, 2009 7:53 am
by seanandruby
Perhaps he meant concrete, which as you know is a mixture of ballast and cement. be very expensive to use just cement, they would never be level and the lot would crack and fail. Lecturer wants to stay off the pish :p
Posted: Sat Aug 15, 2009 7:08 pm
by Richey
I Wasn't watching these guys for long but it looked as if they had made a sharp sand and cement mix (it was fairly dark grey so I'm guessing at least 6:1) completly dry then screeded off to make the bedding course as usual.
Basically I think your saying this is a big no and it wouldn't work. Its not something I've tried myself I was just curious.
As for my lecturer - well he is a walking encyclopedia of knowledge and certainly no cowbow so I'm gonna blame the cute girl. Her name is Anne by the way.
Cheers
Richey
Posted: Sun Aug 16, 2009 8:35 am
by Rich H
Seems to be really common practice. The problem, IMO, is that you end up with a 40-50mm course of sand and cement over a relatively large area, which WILL fail. Think of it as a very thin sheet of glass. The slightlest movement either in the sub-base or the wearing course WILL crack it. . Instead of having a base which spreads the load and subterranean stresses evenly, there will be a concentration of weak points at the cracks. The cracks then become the root for water seepage, collection of dust, migration root for invertebrates, etc., etc., leading in turn to uneven settlement and ruts.
All that aside, it's completely pointless. It doesn't make the drive stronger and it's a waste of time and cement to produce.
Posted: Sun Aug 16, 2009 8:40 am
by seanandruby
Both your posts contradict each other. They were either, "cementing them in" or were using a C B M ??? We dont use cement on it's own for anything rich. If it is a C B M, then your "walking encyclopedia" may be correct.
Posted: Sun Aug 16, 2009 9:32 am
by henpecked
Your making a flexible raft using sand, so the paver's'float' over a 'plastic' surface.
Also, you deal with the drainage issue as the sand will absorb and dissipate the water to and extent. Im sure a solid pavior base will be a real pain in the frosts
Hp
Posted: Sun Aug 16, 2009 11:29 am
by lutonlagerlout
we have come across them,generally speaking a nightmare to work on
i saw a 50 yr old gas board guy making good some CBP on a job of our the other week and he was trying to replace the blocks like setts with a mallet and cementious mix???
i screeded it for him in 30 seconds and it was sorted
i know some lads who lay leanmix instead of type 1,but i just do the normal myself
LLL
Posted: Mon Aug 17, 2009 8:35 pm
by Tony McC
I suspect that we are seeing more incorrectly laid block driveways because of the influx of out-of-work brickies who don't understand pavement construction and assume anything that is mortared-in *must* be better.
We see more and more CBM sub-bases (we are supposed to call them HBMs now: Hydraulically Bound Material) because not enough contractors know how to construct a proper flexible sub-base.
While properly constructed rigid block paving has its place in the options available, it is *always* more labour intensive, requires a much higher degree of skill and needs regular movement joints to appease the inevitable cracks.
Posted: Thu Aug 20, 2009 8:57 pm
by Richey
Thanks for all the feed back. Its not something I would have attempted I was just curious. By the way, this week I saw block paving being laid on soft sand,
what ever next?
Cheers
Richey
Posted: Fri Aug 21, 2009 11:32 am
by Tony McC
One "method" I've come across twice this year is blocks laid directly onto the sub-base. In one case, the client was told that "this is how they all do it that London, and it's just the contractors in the north that are behind the times", while on the second job (currently heading for the courts) the contractor claimed that he had deliberately and meticulously separated the fines out from the sub-base specifically to use them as laying course material. Pillock! 
Posted: Fri Aug 21, 2009 12:35 pm
by lutonlagerlout
nowdays i use a thin a bedding layer as possible typically 25-35mm ,if there was some wonder way of getting the subbase flat and to the falls ,would laying direct on the subbase not work?
LLL ???
Posted: Fri Aug 21, 2009 9:33 pm
by Suggers
so I'm gonna blame the cute girl. Her name is Anne by the way.
Any news on the romantic front? :;):
Posted: Sat Aug 22, 2009 11:04 am
by Tony McC
LLL - one of the functions of the laying course is that it acts as a 'cushion', accommodating the variation in thickness that occurs with concrete and clay pavers. If you lay directly onto a compacted sub-base, you lose that cushioning.
Posted: Sat Aug 22, 2009 9:53 pm
by jay-Manor Driveways
i also try to use quite a thin bedding layer of sand usualy about 25-30mm it seems to compact alot better and is alot firmer under foot when laying ( i only ever really use 60mm's so not really a problem anyway)
laying on the subbase isnt going to work though as you havent got the cushion effect
