Newly laid bluestone squares wet underneath and loose

by Craig H

Stones after they were mortared down and sponged off

Stones after they were mortared down and sponged off

Stones after they were mortared down and sponged off
Loose stone pried up, moisture underneath

I've spent the last couple months putting in a patio with the help of a family friend. We had to build a block wall, backfill, then poured a 4" slab on top. Slab cured for about 40 days. The last major step was done 2 weeks ago, when we laid bluestone squares (2x2) over the slab with mortar. It seemed to go well.

I went out there today to prepare for grouting/tucking the joints, and noticed water squishing out of the edges of about half the flagstones when I walked on them (primarily the ones in the center, but also some edges). Thinking that was not good, I was able to pry a couple flagstones loose with my bare hands. The mortar bed underneath looked very continuous and was a mirror image of the bottom of the stone, so clearly we had good contact. But there was a lot of moisture under there.

Not sure if it's due to all the rain/humidity we've had, or maybe it was a mistake to try and cover the stones with a tarp when it rained, possibly trapping moisture?

Anyhow, now I am wondering how to salvage this mess. Lots of time/labor, and of course the flagstones weren't cheap. Anybody have ideas?

Since the mortar bed looks decent, I am really tempted to re-glue the stones down with some sort of adhesive. I am no mason, but OK with mortar/concrete. However, this experience has me feeling outgunned.


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