Roof terrace paving levels - Slab paving

[DellaP]

I have been asked whether there is any legal or advisory guidance on the levels of deviation for paving slabs, laid on a roof terrace. We have a 40 foot square roof terrace, where the slabs are already laid, and now there is a question of a trip hazard.

While there is an accepted +/- 6mm deviation from specified levels for paving slabs on ground level, does anyone know of anything for a roof terrace? (The spec has come from a Landscaping consultant, who has said they don't know of anything for roof terraces!) As there are manufacturers who make pedestal packings etc for slabs, which can be used on roof terraces, and which can alter the levels of slabs, obviously there is some recognition of a problem.

Any advice would be appreciated.

[Tony McC]

My understanding is that roof terraces are regarded exactly the same as 'conventional' pavements when it comes to standards for tolerances. The market is so small that there is no specific guidance, although that may change with the increased usage of green roofs.