10:1 mix or class iv mortar?

[potts]

Hi fellas,

Discovered this great site the other week and subsequently started planning our 10.2m² slate flag patio using a 50mm 10:1 grit sand cement mix. However... We picked up the flags today (300x300, 300x600, 600x600) and most are only 20-30mm thick, so are actually tiles, by your definition and should be laid on a class IV mortar mix. Would my original (10:1) plan now be too much of a risk?


Thanks again for a wicked site.
Richard

[Tony McC]

I wrote about this very subject for a magazine a couple of weeks ago. Before the country was inundated with imported flagstones from India, 30mm was just about as thin as native stone from Britain or Ireland could be split and still be usable as a flagstone, which is how we came to the deinition of 30mm as the boundary between flags and tiles.

However, the Indian stone is much easier to cleave, and so that are able to create flagstones of just 20mm thin-ness (I can't use the word "thickness" for such a miniscule figure). If these 'stones' were just, say, 300x300mm, then I would be very tempted to refer to them as tiles, but with some of them being as large as 1120x560mm, the world 'tile' doesn't seem quite appropriate.

As for the bedding, stick with the 10:1 and follow the advice given on the Laying Riven Flags page.

[potts]

Thanks Tony, that's just the reply we were hoping for! The thought of digging even deeper for a 100mm concrete base with a 20mm mortar bed on top of that, was scaring the crap out of me. Not to mention the budget...

Superb site with great descriptions in great detail!
Good luck with the book!

Richard Potts