Laying over a pre-existing concrete base - Drainage advice needed

[rosemary44]

Hello

We're planning to lay a patio with readydrive 50x100x200 bricks on to a pre-existing concrete base. We are planning to bed an edging course into cement (the patio doesn't have to support any vehicles- only 8 people + bike shed max). We've just become concerned about the potential problem of saturation- http://www.pavingexpert.com/blokbase.htm . We don't have access to a car and have a minimum of tools hence not wanting to disturb the concrete base we already have. We also weren't planning to lay a sub-base due to the low loads and to prevent making the patio too high. We will therefore struggle to do any of the things recommended on the website. We've had some thoughts on what we can do (below)- if anyone would like to comment on these that would be very much appreciated!

There's also some photos and other info on the project on this thread: http://ext.pavingexpert.com/cgi-bin....&t=5597

Thanks

Ideas

1) Do nothing re. drainage (short of providing a 1:16 fall of the patio surface into flowerbed in front).

2) Bed lengths of rigid plastic tubing running the length of the patio, from back to front, into the cement under the edge course at the front (we were thinking 2-4 tubes 22mm OD pipes). Drill holes in this tubing and wrap in water-permeable but sand impermeable membrane (might a weed-control membrane be appropriate?). Angle the tubing at 1:16 in the drainage direction. Cover in the coarse sand bedding material.

3) Place a thin layer of cement on top of the concrete and bed channels (made from the plastic pipe cut in half length-ways) into the top of the cement. These pipes come out in the cement below the front edging course (maybe leave them as whole pipes there). We could also angle the extra layer of cement we add to the base when bedding the pipes in towards these channels. Place a water-permeable but sand-impermeable membrane above the channels. Lay the coarse sand above.

[seanandruby]

Hello

We're planning to lay a patio with readydrive 50x100x200 bricks on to a pre-existing concrete base. We are planning to bed an e struggle to do any of the things recommended on the website. We've had some thoughts on what we can do (below)- if anyone would like to comment on these that would be very much appreciate


1) Do nothing re. drainage (short of providing a 1:16 fall of the patio surface into flowerbed in front).

2) Bed lengths of rigid plastic tubing running the length of the patio, from back to front, into the cement under the edge course at the front (we were thinking 2-4 tubes 22mm OD pipes). Drill holes in this tubing and wrap in water-permeable but sand impermeable membrane (might a weed-control membrane be appropriate?). Angle the tubing at 1:16 in the drainage direction. Cover in the coarse sand bedding material.

3) Place a thin layer of cement on top of the concrete and bed channels (made from the plastic pipe cut in half length-ways) into the top of the cement. These pipes come out in the cement below the front edging course (maybe leave them as whole pipes there). We could also angle the extra layer of cement we add to the base when bedding the pipes in towards these channels. Place a water-permeable but sand-impermeable membrane above the channels. Lay the coarse sand above.

I would go with the vertical cores as described on the index. you must place some sort of edge restraint to contain bedding layer. also we dont call a C B M just cement, its concrete, or, morter. And we dont use cement on its own there are specialist "grouts " designed for that. good luck.

[Mikey_C]

what about laying it as rigid block paving?

[rosemary44]

This page (http://www.pavingexpert.com/rigidbpv.htm) seems to suggest that a DIYer would find it difficult to lay rigid block paving? We've already bought the materials (i.e. lots of sand and not that much cement), although we might be able to change some stuff if it really would be better.

For the vertical cores, we have no idea how far down the existing concrete goes, and presumably we'd need a very heavy duty drill to get through it? (Can we hire this do you think, could you suggest what we'd need?)

The edge restraint will be the concreted in edging blocks (something like this http://www.pavingexpert.com/edging3.htm).

Just another quick question, some of our sand has got wet with rain water, can we use this in the concrete mix?

Cheers for your replies.

[rosemary44]

PS Anyone know where we can get hold of this Terram 1000 stuff (we live in Cambridge).

Cheers.