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Posted: Tue Jun 24, 2008 7:31 pm
by Davestock
Last September, we had a Pavestone Sahara Sandstone laid as a new patio. There are now various stains (or algae) that have developed on the stone. Is this because they were laid on "blobs" of cement, and the porous nature of the stone has absorbed something? Is there any way we can treat this and remove the stains?
Posted: Tue Jun 24, 2008 10:41 pm
by Pablo
Bloody hell never seen that happen before you need to get your contractor back and hang him by the nostrils thats outrageous.
Posted: Tue Jun 24, 2008 11:21 pm
by Rich H
He's laid it on blobs alright, but it only needs to be cleaned. Soapy water or mild bleach and scrubbing brush, alternatively a pressure washer, should do the job.
Posted: Mon Jun 30, 2008 12:14 am
by Tony McC
Cleaning will provide only a temporary fix. Spot bedding - always a sure sign of incompetence - will cause the markings to re-appear in a few months time.
And two instances of "four corners meeting" only serve to reinforce the sense that this is not a professional flagger.
Posted: Mon Jun 30, 2008 5:08 pm
by Pablo
I can spot 3 instances theres another top right of the photo. 
Posted: Mon Jun 30, 2008 6:46 pm
by surreyhillslandscapes.com
Never seen that before, anyone know why it's done that?
Posted: Mon Jun 30, 2008 9:58 pm
by Rich H
Because it's on blobs there is water under the slabs. This keeps the stone moist where the big voids are. The retained moisture allows perfect conditions for algae and lichens to grow. The moisture isn't transferred as freely where the blobs are bonded to the slabs and therefore those bits stay cleaner.