How to install concrete patio slab?

Kat079

Hi all! I am looking at laying cobbles for a small patio and path area - path will be done at a later time, just focusing on the patio area for now. I have had a read through previous posts but I'm still hitting some confusion.

My original plan was 75mm of roadbase + 25mm of sand + polymeric sand for the gaps to have the cobbles at about lawn height. But I'm wondering if concrete + mortar would be better, and if it would need a roadbase layer. The laying a slab for a small shed section just mentioned pouring the mix over plastic and reinforcements, with no roadbase. The area is 2650mm x 2630mm

I have added a photo of the planned area, and the swing I want to put there.

Any thoughts please!

MitchellMc

Hi @Kat079,

If you're looking to create a cobblestone patio rather than a plain concrete slab, I'd suggest sticking with a well-compacted base rather than pouring a concrete slab underneath.

I'd recommend excavating the area sufficiently to allow for around 75mm of compacted road base, followed by a mortar bed for the cobbles. We hire compactors if needed. The road base should be compacted thoroughly in layers so you have a solid, stable foundation. You can then bed the individual cobbles into mortar, which will provide a more secure installation than laying them on sand and filling the joints with polymeric sand.

You'll need to take the thickness of your cobbles and mortar bed into account when determining your excavation depth so the finished surface ends up at your desired height. It's also worth incorporating a slight fall away from any buildings or structures so water doesn't pool on the patio.

For an area around 2650 x 2630mm, this approach should give you a suitably solid base for the patio and swing without the additional work and expense of pouring a reinforced concrete slab.

Please let us know if you have any questions as you get started.

Mitchell