Would greatly appreciate some help regarding staining on a patio I laid some 12 months ago. Slate paving laid on 6:1 wet bed, SBR slurry to underside of paving and jointed with Rompox Easy. When the patio was finished all was well, I continued working on other tasks at this property on and off for a further 2 months, all was well, made a couple of further visits back over the winter months, again all was well…....until now, over the past month these stains have begun to appear randomly over the paving, the home owners (lovely people) have said that they have not used any chemicals on the paving or contributed to the problem in any way as far as they know and are just as perplexed as I am. Also these stains have also appeared on some un-laid surplus paving that was stored in another area of the garden.
The stains seem to vary in pattern, quite hard and flat, almost cement like.
As the un-laid paving is also affected it would seem not to be an issue with the method of construction, nor immediate environmental issue as the un-laid paving is stored in a different location. Scratching my head a lot with this!! Some form of lichen type growth? There is quite a heavy leaf fall onto the patio area and in the location of the surplus paving, is it possible decomposing leaf fall has introduced this?? I would love to be able to identify the problem and treat accordingly rather than trial and error with a host of chemicals and cleaners. Anyone had similar problems?
There's a blue-ish stain which is reminiscent of one of the pool chemicals used to keep water clear and free of alage, etc.
The big white splodge looks like a deposit of summat. Can you scarpe it off the surface with ease or is it bonded on? If you can scrape it off, does it 'fizz' if you apply a few drops of brick acid?
If it's affecting unlaid paving, then it's likely to originate from the slate itself, but I've not seen anything like this which has NOT been due to the method of installation.
What is the slate, exactly? Name of product and supplier. PM/email me if you'd rather not disclose on a public forum.
We've encountered this problem a couple of times with Slate in the last year, I think it might be calcium carbonate (Limescale), we removed it with Limescale remover and a lot of elbow grease! Also used Drytreat Efferaza and that done the trick as well. Hope that helps
KeburDave wrote:We've encountered this problem a couple of times with Slate in the last year, I think it might be calcium carbonate (Limescale), we removed it with Limescale remover and a lot of elbow grease! Also used Drytreat Efferaza and that done the trick as well. Hope that helps
Thanks for the advice Dave. It certainly looks like some kind of limesclale deposit. I've tried some brick acid on one of the marks and got a strong reaction, plenty of fizzing, and the mark has all but disappeared with some vigorous scrubbing so I've assumed the marks are cement based. Would limesclale react to brick acid in this way also?
I think it would but I am no stone doctor, we've seen it crop up quite a bit on Chinese slate but only this year and we import our own and stock Bradstone and seen it on both, initially it came up on a few slabs on our outdoor display and I couldn't work out what it was, done a bit of research and found this article which is why I think it is calcium carbonate deposits and not cement based. https://ltpuktechnical.wordpress.com/2013....f-slate
Hello Tony, I've seen it on both the Blue/Black Slate and the Rusty, but mainly the Blue/Black, I've got a couple samples in my office with it on, let me know if you want me to send a sample slab up to you, cheers Dave
Hello Tony, we are down south in Farnborough, Hampshire, not far from Guildford so on the Surrey side of Hampshire, GU14 6JD. Feel free to call in, if your passing. Dave
