I've been instructed by HID to lay a slab path.

Because the vegetable bed on on side is some 100mm higher than the existing well tramped down grass path, I'm thinking of putting in treated wood battens either side, weed killing the grass, suitable membrane, gravel/sand and slabs.

The question that I can't find an answer for is if there is a recommended spacing between the edge of the slabs and the wood battens ie how much wider than the slabs should I set the battens?

Thanks for any ideas.