Discolouration of flags - Natural stone flags changing colour

[naturedave]

having laid a patio using Stonemarket market stone grey flags I got a call from the client telling me some of the flags are changing colour. I went to see for myself and sure enough the natural grain in some flags was lined with rust colour and this was spreading through the grain and even through the mortar joints into neighbouring flags. I checked the spare flags we had that hadn't been laid and some of these are also changing colour.

Stonemarket say they will replace the patio and it was simply a "bad batch". Has anyone experienced similar problems ?

[danstan]

I've seen this reaction happen with this colour before

[lutonlagerlout]

i have heard that sometimes they use recycled aggregate for slabs and if there is traces of steel in certain batches then the slabs will "rust"
if they are prepared to replace the whole patio lab+mat then i wouldnt worry yourself too much
its when they claim its the contractor's or your fault that the fun and games start
regards LLL

[Stuarty]

Ive seen it when using granite, atleast their doing the right thing by replacing them.