Slate paving advice please - Will this layout work

[percepts]

First let me say what a super site this is. Factual, to the point and full of useful information and links.

I have been considering using some 600x600 slate slabs in my garden. My idea is to lay a chess board pattern and use pea gravel in the non slate squares. The plan is to use a 10:1 grit sand/cement mix 50mm deep across the full 20m² area, and then lay the slates in a chess board pattern and then fill the empty 600x600 squares with the pea gravel when the mix has gone off fully.
Most of the area will be used only occasionally and one area, down the side of the house, as a path once or twice a week. Very very light use.

The question is this: Will the semi dry mix be OK for this and perhaps more importantly, because the gravel squares will fill with rain, I will make some holes in the bedding of those squares for drainage, but will the slate slabs stay fixed in place or will water at the base edges of the slabs cause a problem? I can leave a 10mm space between corners of the slabs and the rain can run off the bedding to one edge. But will that undermine the slabs?

Thanks

[Rich H]

The mix ought to be fine but I'd be tempted to use a lower ratio and only bed the slabs rather than the spaces as well. Haunch the slabs all around and fill the spaces with ballast topped off with gravel. This way water will drain easily and not compromise the slabs.

I'd also use a wetter than usual mix to ensure adhesion - if you don't get a perfect bond the slabs will end up moving.

[lutonlagerlout]

The mix ought to be fine but I'd be tempted to use a lower ratio and only bed the slabs rather than the spaces as well. Haunch the slabs all around and fill the spaces with ballast topped off with gravel. This way water will drain easily and not compromise the slabs.

I'd also use a wetter than usual mix to ensure adhesion - if you don't get a perfect bond the slabs will end up moving.

ballast will encourage cats to do what cats do all over it mate,i would use type 1 then terram/multitrack then bed the slates straight on this and haunch ,then fill the squares in with gravel after
i know this because we used up some ballast recently like this and cats make a beeline for it
LLL

[percepts]

Thanks, we'll see how it turns out in due course

[paving2go.com]

Hi, most of the suppliers we deal with recommend adding PVA to the mix to ensure good adhesion with slate and also to ensure that edges are not left exposed as de-lamination of the slate can occur.

Pete
paving2go.com

[Tony McC]

...which is only really a problem with imported slate. The native Welsh and Lake District slates, as well as those from Donegal, Fermanagh and Killaloe, don't seem to suffer the same foible.