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Posted: Thu May 31, 2007 10:34 pm
by lutonlagerlout
i found this nice website.
and it is actually quite a good website
clear and concise
but am i alone in spotting a deliberate mistake on the how we do block paving page?
maybe i have been doing it wrong all this time
lemme know whatcha think,here is the website
regards LLL ???
Edited By lutonlagerlout on 1180647404
Posted: Fri Jun 01, 2007 10:34 am
by Tony McC
1 - Too much sand. 2 inches (50mm) plus another 1 inch (25mm) of loose, when the standard to which they claim to comply states that the laying course should be 25-40mm
2 - Only just enough sub-base, but then I'm not sure whether they put down 4 inches and compact it (probably to about 2½ inches) or whether they actually meant they have 4 inches following compaction (which is what it should be, as a minimum)
3 - sanding the joints before compaction. The standard now requires compaction before sanding
4 - the photo of blocks being laid looks as though they've been trampling all over the screeded laying course.
5 - they state that blocks with no natural restraint are haunched with concrete. No mention of them being beddded onto concrete. Haunching alone is not adequate.
Any more???
Posted: Fri Jun 01, 2007 11:16 am
by squire
Tony McC wrote:3 - sanding the joints before compaction. The standard now requires compaction before sanding
Oops.
I recently did some block paving and the supplier (Finlay Breton- Rumbled paving bricks) suggested that as they had a straight edge, they should be sanded first and then compacted.
They told me that chamfered edge blocks should be compacted before sanding.
I've more to do still so I wonder Tony, if you could just confirm that both types should be actually compacted first or do they have a point regarding above. Should I expect any problems with the paving I have already done? It seems fine but is only down a month or so.
As for the website, why do they put the sand in two layers? Why not just put down the bedding layer, compact and screed?
Posted: Fri Jun 01, 2007 7:38 pm
by lutonlagerlout
it was point 1 that i noticed straight away, didn't know about compacting before sanding
i was under the impression that sanding before compacting allowed the KD to fill any voids under the blocks.
shame really because the website is quite clear and concise.......
LLL 
Posted: Mon Jun 04, 2007 9:53 am
by Tony McC
The "recommendation" contained within BS 7533:3 changed in October and the received wisdom now makes a big thing of a process called "Compliance Checking", which basically means checking that the blocks are properly laid and aligned before filling the joints, because, as we all know, once the sand is in the joints, the blocks are an absolute bugger to lift out of the pavement.
So, the idea now is to compact the blocks (whether they are chamfered or rumbled) first, then to check for compliance, including the replacement of any blocks damaged during compaction, then sand the joints and finish off with just one or two swift passes with a plate compactor.
There's a simplified version of the construction sequence flowchart here which outlines the current thinking.
Squire: as you can see on the flowchart, chamferless blocks are indeed jointed then compacted, but I'm happy to see rumbled blocks classed as chamfered and therefore compacted first.
LLL: there really shouldn't be any voids beneath the blocks for jointing sand to fill. If there are voids, that suggests a problem with the screeding and/or the bedding material.
Posted: Mon Jun 04, 2007 9:26 pm
by lutonlagerlout
when i first did block paving 20 years ago (this month to be exact) we had never really seen it before (used to be concrete drives all the way till then or tarmac) we had a rep out from whoever .
anyway he basically ran through the spec with us (mind you the blocks were 90 mm then) and the bit about KD filling any slight variations and voids came from him,also told us to use scaffold poles as screeding bars
and that was the total 1 hr of my training on block paving and patios,the rest has come through trial, error ,and word of mouth
roll on the HLTG
cheers
LLL
Posted: Tue Jun 05, 2007 8:27 am
by squire
Tony McC wrote:So, the idea now is to compact the blocks (whether they are chamfered or rumbled) first, then to check for compliance, including the replacement of any blocks damaged during compaction, then sand the joints and finish off with just one or two swift passes with a plate compactor.
Squire: as you can see on the flowchart, chamferless blocks are indeed jointed then compacted, but I'm happy to see rumbled blocks classed as chamfered and therefore compacted first.
I wouldn't have considered them chamfered but your explination makes perfect sense. Thanks Tony.
Edit: Compacting the blocks did result in a couple of them being damaged (slight chipping at edges of cut blocks). I didn't fancy pulling them out and replacing them and they add to the "rustic" feel (that's what I told herself anyway 
)
The thing is, if they had not been sanded first I more than likely would have replaced them, so point taken.
Posted: Tue Jun 05, 2007 2:09 pm
by Nigel Walker
I understand where Tony is coming from and the new British Standards, but I have been laying block paving for almost 20 years and over that time have used various methods for screeding, compacting sanding etc and from my point of view I have found what works best for me. And that is - sanding the joints prior to compaction. I have never had a problem using this method. Especially since I started using Tobermore products 2 and half years ago. In that time I have not had one single block that needed replacing either chipped or broken. That is using somewhere between 15,000 and 18,000 square metres of Tobermore blocks without lifting and replacing a single block.
I have on one occasion compacted the blocks prior to sanding and experienced lots of problems with alignment. Had to spend about 2 hours straightening all the blocks before sanding and then compacting again - nightmare !
Sorry Tony but I am gonna stick with my method. Its worked for years and as the saying goes - If it aint broken dont fix it
Nigel
Posted: Tue Jun 05, 2007 2:20 pm
by mouldmaker
Nigel Walker wrote:Sorry Tony but I am gonna stick with my method. Its worked for years and as the saying goes - If it aint broken dont fix it
Nigel
Off topic, but it reminds me of recent changes in CPR technique. It's different to how I learned when I did my first aid course.
I presume that if I continue doing it the old way, people will now die whereas before they would have been saved.
Posted: Tue Jun 05, 2007 7:13 pm
by Paverman Dan
Tony McC wrote:4 - the photo of blocks being laid looks as though they've been trampling all over the screeded laying course.
In the photo right before that one you can see the footprints all over the final inch of sand, which I'm not a big fan of even before its been screeded. I suspect they may have laid out too much sand at once before paving.
Also, it looks like the property slopes away from the garage . . . if so wouldn't you snap 90 degree lines from the garage to the street (like in Tony's book) and start laying from the street and working your way uphill? Maybe thats what they were trying to do with the paving on the left hand side, but if your going to do that why not just lay the entire driveway apron and work up to the garage rather than doing the driveway in patches?
Edited By Paverman Dan on 1181067384