Permeable bedding

[seanandruby]

is it best to leave the bedding high as in ordinary bedding, if so how many ml will it wacker down? Need to re-instate a large area and has to tie in with existing b p. Can't look in index as only have phone and it takes ages.

[lutonlagerlout]

the gaffer will probably give a definitive answer later ,but i found this
"Not only is the laying course material free of fines, which dramatically affects its handling and compactability, there's more of it. The recommended thickness of a laying course in a conventional pavement is given as 25-40mm, but for permeable pavements, the recommendation is an even 50mm. This increased thickness is used to accommodate the rather limited compaction that takes place with this type of aggregate - apparently, consolidating 50mm thickness gives more reliably consistent compaction than is the case with 40mm or even less. "
reading the above,I would imagine that it would only be marginally high sean say 5mm then screeded off
the whole idea of permeable paving makes me think of a large water feature

LLL

[rab1]

you really mean pond, seen a few (lot) of permeable jobs laid and then changed on one side (car parks) to normal mono block as the whole thing turns into a pond.

[Tony McC]

There's very little compaction/settlement in a genuine permeable laying course (6-2mm). On a typical 50mm layer, I'd say there'd be no more than 4-6mm.

You get a good indication when prepping the laying course. If you spread the grit, rough it out, and run the plate over it before screeding, you'll see just how little it goes down. There needs to be a little bit of give in the laying course for when you consolidate the blocks, but it really will be just a very few millimetres.

[mickg]

>>>>>>when you consolidate the blocks
just for the record you don't consolidate the blocks with Marshall's permeable paving, once they are laid you brush the 6mm clean aggregate in the joints and the paving is finished

the 20mm clean sub base and the 6mm clean laying course are lightly compacted only so like you say there will only be a few millimeters compaction

[lutonlagerlout]

has anyone here actually done permeable paving on a domestic driveway?
i wouldnt have it for sure
I could see it working at seaside locations, but not in the clay of southern england
as for weeds?
LLL

[Tony McC]

Mick,

despite what you might have been told, it's still a good idea to consolidate the blocks once they're laid and jointed as it helps settle the jointing, creating more interlock and it also helps 'iron out' any minor uneveness between blocks. Clause 5.4.7 of the latest edition of Part 3 makes no exception for CBPP.

LLL - I've been involved on about 16-20 residential CBPP projects over the past 12-15 months and I reckon at least half of them were inappropriate for the site conditions. I've been building up a library of photies that show what CBPP looks like after a few months because I don;t think the pristine inages used to sell the concept are fair on customers who start to complain when the joints 'moss up'.

When it works, it's fantastic, and it should be used on every commercial project unless an unarguable case can be made for it not to be, but I'm less convinced for residential driveways, where, in many instances, standard paving drained to a soakaway or a rain garden is a much better and cheaper option.

[rab1]

see a hell of a lot of this on sites and after 6mths you cant see the small stones for crud or the stones have gone completely. big thing you see is that half is done in normal blocks and the other is done in permeable blocks.

[lutonlagerlout]

well when you see trees growing out of guttering and old brickwork,imagine what is going to happen when seeds germinate in that lovely gravel,with a fresh supply of water and odds and sods of bird droppings etc to supply nutrients
if the ground is suitable i.e. chalk sandy or gravel then acos and a soakaway are surely a better option
the only time i can see this working is where the paved area is elevated to allow the water to run away properly
I was reading the new scientist the other day (geek i know) and the total paved area in the uk (roads drives patios) is under 2% of surface area
drives make up maybe 5% of this i.e. 1/1000th of the uk is driveway,do i believe this makes any contribution to flooding?
no, in a word
stop building houses on flood plains is the best start
LLL

[mickg]

I totally agree with you Tony, just saying what I was advised to do with the Marshall's product

[seanandruby]

thanks for your help. It's as I thought, 'leave it a few ml proud.' The initial job has been down about 12 months and is still in the wrapper, ( so to speak) not driven on yet. Got a lot to take up to upgrade some ducting. A right pain to take up, although the head of an acrow does a good job.