Using ballast as sub-base

[AndyBenn]

Hi,
Great site, been ploughing through the archives and it's all been very enlightening, much better than work!

I'm about to start work on extending an area of existing patio to replace an area of lawn and to provide an extra row of flags down the side of the house. I've calculated it's approx a 36 flag job, at 600mmx600m, so about 13 meter square.

My question is with soil as the sub-grade and dug out to a suitable depth, should I use ballast as a regulating layer (no cement added) over the soil to provide a suitable base and then bed the flags with 10:1 mix? Or, would a ballast & cement mix as the bedding layer straight on to the soil be a worthwhile option?

Would a rubble/DTp1 base topped with a 10:1 bedding mix be better than using ballast.

The soil from what I've experienced gives moderate drainage but I imagine has quite a high clay content.

Many thanks, for any pointers.
Andy

[danensis]

Depends what you mean by "ballast". Where I come from it was sharp edged stones around 22mm to 25mm, but round where I live now it is an unspecified mixture of gravel and sand, used for making an unregulated concrete.

[AndyBenn]

The balast was stuff I'd seen down B&Q, of mixed size gravel and sand with max gravel size of (I think) 20mm.

My concern is getting the sub-base right for the bedding layer. Whether that's to just compact the soil once the lawn area is up. Or to dig more soil out and have a regulating layer (say 25mm?) of whatever substance is most appropriate.

Cheers

[Tony McC]

I've seen the stuff B&Q sell as Ballast and it should be ok. However, as I say time and time again, a sub-base is not essential for a patio: it can be useful, especially in areas of bad ground or where levels need to be elevated, but it is not esssential.

A simple bedding layer of 50mm of 10:1 grit sand with cement is usually adequate for most patios and garden paths