The Brew Cabin

Posted: **Wed May 09, 2007 8:53 am**

Hi,
My Fiance and I are turning the crazy paved front garden into a driveway but are paving newbees. Reading the crazy paving section on this site it recommends using C20 Concrete base to 100mm thick but also mentions a sand and cement mix and using a sub-base of aggregate. As the driveway will be sloping down to the curb at a 25-30degree angle whould we still be able to use a concrete base and if so do we have to wait for the concrete to dry before putting on the crazy paving as I cannot figure out how it would stay in place if its not wet. I see about the wet grouting - would that be sufficient to hold it in place? Any ideas would be gratefully received.

Posted: **Wed May 09, 2007 6:16 pm**

At such a relatively steep gradient, laying onto concrete is preferable, but as you've spotted, using a very wet concrete would present problems of its own. So: you use a very stiff mix or a semi-dry mix.

There are two construction strategies: in the first, you lay a concrete base, and then lay the flags onto the base via a mortar bedding layer. The alternative is to bed the flags directly onto the fresh concrete.

If you opt for the first method, then it would make sense to buy-in the concrete as ready-mix, have it all delivered in one, and get the base laid in one day (in a couple of hours, actually), which then allows you to lay the paving at your own pace. The concrete needs to have a low slump - say 25-40mm, and it should be levelled out with rakes and then compacted with a vibrating plate. Start discharging at the top of the slope and work your way down to the kerb. You will need to think about movement joints, so read up on them on the main website.

The alternative strategy, as mentioned, relies on bedding the flags directly onto fresh concrete, and because cray paving is such a slow process, you can only place the concrete base a bit at a time, so it's easier to site-mix your own concrete, churning out a barrowful or two at a time, spreading it, laying the flag pieces, and then mixing another batch.

When it comes to laying, it's easiest to start at the bottom and work uphill.This helps prevent pieces slipping away from you as you work.

As for the jointing, a stiff-ish slurry will not flow too far down hill, but washing-off may cause a few problems. To be honest, I'd look at using a good quality polymeric, such as GftK 840 or Romex, because traditional mortar jointing will take as long as the laying, if not longer.

The Brew Cabin

Creating a driveway using old crazy paving - Concrete versus sub-base