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Posted: Mon Jun 09, 2008 4:31 pm
by Alladin
Hi,
I'm a newbie to this site and construction so hello everybody. I'd like some advice regarding block paving. My builders have told me they are going to lay concrete, sharp sand and paving blocks after removing my existing tarmac. I thought MOT type was was recommended. Could you please advice me whether concrete is a suitable substitute for mot type 1. I'd appreciate your comments, thanks.
Posted: Mon Jun 09, 2008 5:45 pm
by Rich H
Block paving is usually laid as 'flexible' paving. That is to say that the sub-base and bedding course are of unbound materials and the paving blocks are not physically jointed, rather the joints are filled with a very fine sand (kiln dried sand).
The advantage of flexible paving is that, over a large area, it can accommodate movement in the sub-grade (the soil, etc., below the layers of the drive) without becoming damaged. If the ground sinks a millimetre or three in one area but not another over time, it's not the end of the world.
With rigid paving, it is absolutely vital that the foundation is, in as far as possible, utterly immovable such that the rigid surface doesn't crack or break up. Any minor movement in the subgrade must not impact on the sub-base to the extent that it affects the pavement, beyond the built-in measures to alleviate stress.
Both methods of paving are widely used in all sorts of applications. What is dodgy is to mix the two in the wrong application. The problem with concreting under block paving (apart from being far more expensive than just laying Type 1!!) is that it is rigid and impermeable. Firstly, it will be possible for the concrete to fail under stress, and fractures will occur. Along these fracture lines, further stress will cause the drive to gradually sink. Just as importantly, as moisture enters the bedding layer of sand through the blocks (gradual but inevitable) the sand will eventually become fluid, at which point the drive will fail completely.
Why are you not using a landscaping or paving company to do this, rather than a builder? (with the greatest of respect to the builders of this place 
)
Posted: Tue Jun 10, 2008 1:04 pm
by Alladin
Hi,
Thanks for the advice. As to why I'm using a builder - cost. It may sound stupid but I haven't gone for the cheapest quote either. Some landscaping companies were quoting around £10,000 for laying a 42m2 area. I thought this is ridiculous no matter how many different ways they convinced me they were "experts" in the field.
Posted: Tue Jun 10, 2008 7:10 pm
by Rich H
£10k! Can I quote!?
Seriously, though, it's hard to judge without knowing the site, the block type, the kerbs, etc., but even £100/m should cover nearly all situations! For 'standard' 50mm pavers with same for edging it shouldn't be more than about £60-£70/m+VAT.
Whatever you do, though, don't use a guy who'd put a rigid base under a flexible drive. Remember, that's just the bit you know about!
Posted: Tue Jun 10, 2008 9:27 pm
by surreyhillslandscapes.com
As Rich above says, you should be looking to pay no more than three grand really, I would be happy to quote for it if your in the Surrey area, but I would definatly steer clear of the builder option, most don't have a clue when It comes to paving, ripped up a five year old block paved drive only last week, was constructed with a concrete base, customer told me that the builder did such a good job on his garage ( which he had) that he let him do the drive. Bit like asking me to build you a extension because I did a good job on your patio..
Posted: Wed Jun 11, 2008 4:25 am
by lutonlagerlout
dont forget its "landan " the OP lives
my mate is a scaff and he has got to spend 10k on a newish flatbed thanks to red ken's barmy emission zone stuff
10k though sounds like a chuck a big quote at it and see what happens, i would say around £75 per M2 + for block paving and £100 per m2 for patios
LLL
Posted: Thu Jun 12, 2008 9:53 pm
by Tony McC
I'm sure we've covered this at least twice in recent months. While there's nowt wrong, structurally, with using a concrete base beneath flexible block paving, it creates a whole new set of problems, primarily that of adequate draining of the laying course.
More worryingly, concrete bases beneath residential pavements do seem to be used mostly by those so-called contractors who simply don't have the requisite skills to construct an adequate sub-base. If they can't lay and compact crushed aggregate, would you really want them laying blocks?
There are genuine and important reasons for using concrete bases instead of (or as well as) flexible sub-bases. If the project features such reasons, then there's no issue, as long as the contractor makes adequate provision for draining the laying course, but, as I said, most such installations on private driveways are unwarranted and a mask for incompetence.