Forum: Flags and Slabs
Topic: Sorry state of kandla grey patio now chalky white
started by: Smiris

Posted by Smiris on 07 Oct. 2019,19:37
Hello all,
Unfortunately I canít upload photos as iím not very clever! But we bought London Stone tumbled kandla grey sandstone in July and had it professionally laid on a full bed of mortar to London Stoneís specifications. Two weeks ago it started discolouring. Itís covered in a chalky white residue that London Stone says isnít efflorescence but is down to dot and dab. But there are no circles iíd normally associate with that. Our landscaper is willing to help but equally flummoxed. Could it be efflorescence? A fault with the stone? Something to do with the tumbling process? Any ideas most welcome!

Posted by Smiris on 07 Oct. 2019,20:11
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Posted by Smiris on 07 Oct. 2019,20:12
Worked out how to attach pics. The first one you'll need to copy and paste.
Much appreciate any replies!
Thank you

Posted by Tony McC on 08 Oct. 2019,11:52
I don't think that's eff: I think it's cement staining caused by the clueless eejits that laid the stone so badly in the first place....just look at all those amateurish crossed joints!

It certainly looks like cement hazing, probably from the jointing process - did you see how they did this part of the work?

The photies are small, which is mlimiting my certainty, but I'm 90% sure it's cement haze, and, assuming I'm right, it's going to be a bloody nightmare to rectify because, as good a stone as is Kandla Grey, it is unfortunateloy susceptible to acid and so I can't recommend such a cleaning method.

There are dozens, possibly hundreds of similar threads in The Brew Cabin about cleaning cement from Indian sandstone - run a search using the buttons above, but don't build-up your hopes!

Posted by Smiris on 08 Oct. 2019,12:01
Thanks Tony. What a nightmare!
The contractor had two of them working on it with the hosepipe going the whole time. It was the hottest day of the year though!
Does that mean the whole thing will have to come up?

Posted by Tony McC on 08 Oct. 2019,13:12
Not nesser celery!

It *may* be possible to clean it in-situ, but a specialist would need to see it at first hand and determine just how severe is the staining and how likely it is that repeated mild (phosphoric or citric or similar) acid washes would work, or whether something more drastic is required. Replacement would be the last option, but sometimes, it's the only way.....sadly!

What you need now is for the ever-charming Roger the Cleaning Guru to come along and give you more detailed advice......or lok up some of his many previous postings on this same subject.

Posted by Smiris on 08 Oct. 2019,13:28
Thanks again. I feel I donít trust anyone now!
Hope someone on here can advise?

Posted by Smiris on 08 Oct. 2019,13:42
Hello again.
Just to check. Could a resin based mortar do this? That was what was used.

Posted by R&A Pressure Washing on 09 Oct. 2019,10:56
Quote (Smiris @ 08 Oct. 2019,13:42)
Hello again.
Just to check. Could a resin based mortar do this? That was what was used.

Yes a resin based mortar can do this unfortunately, it can be removed sometimes just takes time etc, noticed you are in the London area?
If you want to email me the photos as well, and let me know what part of London, I can come over possibly one day next week, try a few things to see what removes the stain, as sometimes it isn't as easy as saying use X product etc. My email address is in my signature just below.

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