Sawn cut sandstone - Help

[dukeyfilm]

Hi had approximately 20m2 of sawn cut tint mint sandstone laid 3 weeks ago and although after drying out in this hot weather there are some strange 'stains' and marks. I have contacted both the stone supplier and the contractor who have both said see what they are like once dried out. I am about to go back to them but just wonder if anyone has any advise on what they think it might be. There is some efflorescence but there seems to be circular marks ( from cutting / smoothing fabrication ?), stripes (natural grain?) and dark staining( no idea)?
I have included photos taken 1 week : http://s1052.photobucket.com/user/dukeyfilm/library/Patio%201%20week
and 3 weeks after completion : http://s1052.photobucket.com/user/dukeyfilm/library/Patio%20week%203
Any ideas?
Cheers
Mark

[Tony McC]

These comments are based on the photies you posted, not on an actual assessment of the paving itself.

The circular marks are a result of the vacuum lift used to moved the flagstones around the factory. Mint is a very porous sandston and it's likely that the vaccum drew fine particulates into the surface of the stone which have then created what looks like a perfectly circular stain. This may or may not weather out over time.

Other stains are reflective mortar stains, caused by the thirsty flags not being primed on the underside prior to installation and then laid onto a wet mortar which has had some of its finer cementitious paste sucked-up into the stone by capillary action. This is a permanent stain, more or less - this type of staining tends to hang around for at least 3-5 years.

So, you have both: manufacturing "issues" and installation faults. It's unlikely you'd get anywhere with the manufacturing problem as the supplier will claim it is part of the manufacturing process. Had you bought this stone from one of the 'quality' suppliers, they would most likely have had systems in place to ensure this type of 'stain' can't happen, or it would have been picked out in the quality control stage, but with 'budget' suppliers, this is fairly typical.

Installation is easier to pursue for negligence. No matter what the installer says, they, as so-called professionals, should have been aware of the potential for eaxctly this problem and taken steps to prevent it occurring.

[dukeyfilm]

Thanks for the reply Tony. Both your explanations make sense and I will be taking it up with the installer. I do have some spare stone and I will ask him to replace the mortar stained pavers, making sure he primes them properly. As to the manufacturing issues, not much I can do I suppose. They were a budget stone (£20 per m2), but I would have hoped the installer would have picked up on it and raised it with me before he went ahead and laid them. At least I could have approached the supplier. But time is a constraint and he probably wanted to get the job completed ASAP and onto the next job and not be held up whilst new stone was supplied!
Quantity not quality!
Thanks again for the advice.

[Tony McC]

20 quid/m² for honed stone, even Mint (which is best used as skip ballast, IMHO!), is way too cheap for quality.