Riven sandstone paving - How riven should it be?

[bodgeitandscarper]

Hello again, due to the bad weather I've taken a patio break and started again today. I have two packs of calibrated paving and paid a good price (not the cheapest) I've had problems with iron in most of the slabs but that's fine I can handle that now the only other thing is the slabs in the outside of the pallets are decent slabs a little riven but not bad, as I get further into the pack the slabs become more riven and some dips are 5mm plus with bits delaminating. I've contacted supplier previously regarding iron but now with this problem I don't know if I'm becoming too picky. When I worked as a landscaper previous my gaffer would buy the cheapest paving and it would look like this. I could post pics but got no idea how too! Am I being too picky?

[Tony McC]

There *is* a limit of tolerance for the variation between high points and low spots on a riven flasgtone surface. It's covered by BS EN 1341 which sets the permitted tolerances. In short, a flagstone *can* be too riven.

We use a profile gauge to assess whether any particular flagstone falls within the tolerances, but, for what is sold as 'patio paving', unless the supplier declared conformity and compliance with BS EN 1341, you might not have a case and would therefore have to rely on the good will of the importer.