Laying a new patio - Sub-base always needed?

[Gazanimal]

Having read the various topics on the main website I'm just wondering if having a sub-base is always necessary?

My situation is that I'm looking at laying approximately a 14-16m2 patio. The area was dug out about 2 years ago when we had the concrete base done for our pre-fab garage & I'm now getting round to sorting the lower area.

There's a couple of rows of existing 450mmx700mmx50mm flags near the house which I'll keep but will join the new area up to them. Outer borders will be graveled etc and the patio will be very light usage, only a path way to the upper garden level will see much use.

Currently the ground is just a compact soil was formally a lawn area, but it's been down to soil level for about 2 years now.

Do I need a hardcore base? Or can I bed straight onto a sand/cement base?

Thanks for any advice, I like to read up as much as possible, but always nice to have clarification.

[seanandruby]

Hi Gaz. No you don't always need a sub-base, it depends on the condition of the sub-grade.

[Gazanimal]

Thanks Sean.

I know the soil is quite compact & very clay-like. It's a real pain in the ass to dig tbh. The garden does slope quite a bit from upper level to house, but there's existing steps to upper level.

From the image below you can see where the existing grass level was, so there's about 100mm fall from wall to exisiting patio area.

Here's a quick image of what it looks like (taken 2 years ago)



The facing wall was done before me moved in, so excuse the sloping But it'll be hidden by a raised bed eventually.

Should I compact it down or leave it as it is & use a sand/cement bed?

[seanandruby]

How much are you going to raise it by, how much bedding?

[Gazanimal]

Well I don't want to raise it too high, from the picture you can see the path at the side of the garage which is part of the garage base so I don't want to go over that. That's about 80-100mm iirc so probably a 40-50mm bedding then 32mm flags on top.

The bedding will have to be slightly less towards the house as the existing patio area is at the lower end of the slope

[seanandruby]

At that depth for a 32 ml flag i'd go for a lean mix concrete.

[Tony McC]

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