Flagstone Over Concrete

by Chris
(Buffalo, NY)

I am re-laying flasgtone over an existing concrete patio. I had to pull the entire thing up as all of my joints were crumbling and the flasgtone was no longer adhered to the mortar base.


Some of the pieces that I have are only 1/2" thick. I was originally going to replace all of these pieces with 1" thick.

My questions is, can I still use the 1/2" thick flasgtone when mortaring back onto the concrete? Or will that be too thin and present a problem in the future. I want to do this right the first time.

I live in Buffalo, NY. I am planning on mortaring down the flagstone and then using polymeric sand for my joints (1/2" wide). The flagstone is all sqaure cut, not irregular. Should I mortar the joints? If so, is the mix the same as the mortar for laying them down?

Comments for Flagstone Over Concrete

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re-laying flagstone on slab NEW
by: Richard

Provided your slab is in good shape, you shouldn't have any problem laying the half inch flagstone back down. We've done that many times. 1/2" flagstone coverage is around 165 sq.ft. per ton and it goes along way. Obviously a much thicker stone has to be used if it is not on a slab. Polymeric sand should do fine as long as you keep the joints from 1/2" to 1" wide.

Good luck

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