Decorative slate chippings - sub base required?

[chrisall]

I am planning on using decorative slate chippings in our small front garden (approximately 15m sq). I have removed the turf and the thin layer of heavy soil that the builder kindly spread over the lumps of concrete, broken bricks, tiles etc. In total I have probably excavated down to about 4 inches in places. I was wondering what I should use as a sub-base under the 2 inches or so of slate that I'm putting down? I don't really want to use just the slate if possible as I think it would require around two tonnes & it's quite expensive.

On the subject of the slate chippings, I know that it comes in 20mm and 40mm ... is one recommended over the other for some reason? Most of the gardens I have seen use 20mm but it just looks a bit small to me, I went to IKEA the other day & they had some of the larger size around some trees & I thought it looked better... I know it's a bit sad that I've been taking an interest in other peoples slate chippings, lol.

Cheers,
Chrisall.

[Dave_L]

If the ground is stable I wouldn't bother with a sub-base for a decorative chipping area that isn't going to be trafficked either by foot or by vehicle.

I'd dig off 25mm of so and lay the chipping on a sheet of 1200 DPM to stop any weed breakthrough.

20mm too small and 40mm too big? Buy some of each and mix it in.

[seanandruby]

i've got my path 40ml deep, laid terran and spread the slate. Not a weed in sight for nearly two years.

[chrisall]

Thanks for the replies chaps. The only reason I was thinking of using a sub-base was to reduce the volume of slate & hence the cost.

Cheers,
Chrisall.

[Rich H]

The solution is to buy either top soil or sharp sand, whichever you can buy for less, locally. Rake this to a level and then put the membrane over the top.

You will find that you need less 20mm than you do 40mm to cover the membrane. Lay it as thin as possible to minimise cost.

[Pablo]

There was no need to remove the existing soil even if it was rubbish. If you are covering it in slate then who's gonna see it.