I have noticed that many of the indian sandstone slabs I had laid 3 years ago are developing lots of unsightly dark 'spots', as shown in these images:
These marks cannot be removed by a pressure washer, and appear to reach down into the stone itself. I started to notice these stains last year, but this year there are a lot more of them. Not all the slabs are affected as you can see in the photos. Can anyone tell me what is causing this problem and what I can do about it? I'm worried that this will continue getting worse until my entire patio is black! Is there a name for this problem?
Is this a case of defective stone? Should I be demanding replacement slabs from the supplier or the company which laid (and supplied) the slabs?
i think the gaffer has got it in one,but i do have an alternative theory/example
my dad's patio suddenly developed brown spots all over it,which puzzled him,the next day his garden furniture developed them too which made him very concerned,then my mum's wishing well got it too
it was then that we realised that the plonker in the garden behind was using one of those nifty cuprinol spray gun thingys,and every time he went past a knot hole or got to the top of his fence he sent a fine spray of cuprinol over to my dad's patio etc
dad has now made it clear what to expectif he tries using it again especially as he now has a nifty sandstone circle and new furniture (built by you know who :;):
cheers LLL
I'm fairly certain David's spots are lichens, but I know what you mean about those bloody sprayers. I've had half a dozen emails over the weekend about how to clean up drips from paving (answer: I don't know - I've never used the damne stuff!)
What struck me about that recent advertising campaign, though, is that, if the stuff lasts for 5 years, why would you splurge a load of money on some single-task tool that is going to gather dust in the back corner of the shed for the next 4 years and 364 days?
