I have a question whose answer I cannot find anywhere in old posts, so if it has been answered before then please excuse me.
I've just laid a sandstone patio (Indian sandstone FWIW). It's on a dry-mix full bed, which is in turn on a 75mm+ sub-base. Looks great I think, but I have one concern. Around a couple of slabs there are damp patches that seem to be very reluctant to dry out. Photo shows pretty clearly, and though I took this this morning when it had lightly rained, they are visible when it has been dry for days. To avoid the obvious Q's, there is a fall, so the slab isn't the 'last puddle' after it rains
It used to appear on another slab that was laid earlier (it took a while to finish the patio thanks to the bloody awful weather this year). That doesn't show it any more, so I was wondering if this was the ground drying out slowly through the slab (about 8 inches below the sub-base it's solid clay, so drainage is v. low), or something more 'sinister' (aka user error).
Don't worry, this happens with new paving of porous stone. It's more to do with the final curing (I think) of the mix than anything else. You won't see it next year. Usually happens with the pointing joints, too, in the first year.
