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Posted: Sat May 12, 2007 1:12 pm
by 102-1177964440
I have removed about 1 metre wide of “crazy paving�, on a driveway, to install a drainage pipe under it. As the regulations say, I placed 50mm thick (900mm wide) concrete slabs over the pipe spanning the trench. I have allowed for a 30mm gap between the top of the slabs and the underside of the paving stones. The latter are made from broken concrete 50mm slabs. The existing paving is resting on a thin layer of 10mm gravel which in turn is resting on tarmac about 120m thick. The paving has mortar on the joints, fairly wide in places.
My question is, in order to replace the paving stones I removed, which is the best technique I can use in my situation to fix them so that they will not rock or sink with the weight of the cars?
Here is a picture of the driveway (if it works)
Thanks in advance
Posted: Sat May 12, 2007 4:12 pm
by lutonlagerlout
As the regulations say, I placed 50mm thick (900mm wide) concrete slabs over the pipe
what regulation is that then fred????
on a driveway most pipes would be encased in leanmix concrete,then use concrete to bed your crazy paving back in
what you have shown there is not a great idea IMHO
anyone else?
regards LLL ???
Posted: Sat May 12, 2007 4:38 pm
by Stuarty
first time seeing/hearing of this method. Anytime ive done such work its been done in the way LLL described above.
Posted: Sat May 12, 2007 6:40 pm
by seanandruby
how wide was the trench? how deep are the pipes? what did you surround them in? what did you lay the flags on? i know thats a lot of qs but just want to get some idea how stable the sub base is. like the others ive never laid and covered pipes like that, and deep drainage is my job. where did you read the regs for tha?
Posted: Sun May 13, 2007 11:35 am
by 102-1177964440
Hello,
To clarify my construction I am posting this diagram:
When I said regulations I meant a combination of the NHBC ones and installation instructions by pipe suppliers like Marley. I am talking about where they say that pipes under 600mm deep from the top surface should have a concrete slab above them. If they are 900mm deep (under driveways) they only need compressed backfill.
My understanding is that only rigid pipes need to be encased in concrete and that flexible pipes only need to be surrounded by 10mm pea gravel. But I am seeking advice...
Posted: Sun May 13, 2007 11:48 am
by Tony McC
The 'flag over' method is a bit OTT, but it is a recognised construction. However, I'm not sure where you've got the idea that flexible (uPVC) pipes shouldn't be encased in concrete: they need it more than do clay pipes, because they are incredibly prone to deformation under load, and while pea gravel will cushion them from the weight of the backfill, when it comes to traffic, they really do need a bit of support.
Anyway, on to your bedding problem. Just lay your crazy paving pieces onto a mortar bed. Use 6:1 mortar, because of the vehicles, and add a plasticiser to make it workable. Although I like to use a semi-dry mix whenever possible, a moist mix would be better for this project as you need to create a bond between flag-cover and the crazy paving.
Posted: Sun May 13, 2007 9:49 pm
by lutonlagerlout
yes but my point is that as with laying slabs on slabs ,that if one of those 3 be 2 's should fail then so will the crazy paving on top of it
btw round these parts the BCO makes us encase all upvc pipework in 100mm leanmix when under a building or driveway
cheers LLL
Posted: Mon May 14, 2007 1:36 pm
by 102-1177964440
Both the Council and NHBC inspectors came and saw that we were encasing the pipe in gravel and were satisfied. My main concern was to know that the concrete slab was strong enough for the drive. Tony McC even thinks it is OTT. Any other comments?
Posted: Mon May 14, 2007 8:22 pm
by simeonronacrete
For extra bond and security you can use Ronafix in the mortar. Dilute 1:1 with water and the bedding will be much stronger.
Posted: Tue May 15, 2007 8:32 pm
by 102-1177964440
Thanks for all the feed back. I wanted to use the Ronafix stuff but my mechant told me today that it was £42 per 5L container (I would need 4) + £60 delivery + 3-4 working days to deliver, so I am afraid I am going to use Tony McC's mix.
Posted: Sat May 19, 2007 7:56 am
by seanandruby
don't mean to be pedantic. but why the 250ml back fill? was it an over dig? if so did you wacker it in, or, make it up with shingle?
Posted: Sun May 20, 2007 12:06 pm
by 102-1177964440
Yes it was overdigging because the contractor said to put the drop in pipe level at the inspection chamber, with a tumbler system, after we had done the digging for the pipe at the bottom.
We compensated by putting 100mm of sub-base crushed material so that it would not just be soil. There was no way that we could get a whacker plate down there (and then lift it) so we compressed it by hand.
Posted: Sun May 20, 2007 2:33 pm
by lutonlagerlout
so we compressed it by hand.
hmmm how exactly do you compress by hand?
you can get narrow wacker plates for trenches
cheers LLL ???
Posted: Sun May 20, 2007 2:41 pm
by seanandruby
......Or self compacting shingle :;):
Posted: Sun May 20, 2007 4:39 pm
by Stuarty
Or what about those tamper rammers i think they called - you know, the pogo stick with an engine on top 