Sandstone staining

[andymoz]

Guys, I have a question.

Firstly, credit to this website, which became the core source of information from substrates and mixes to the choice of sealer.

I completed a large self-build project, towards the end of last year, however staining or pigment has formed along the front row of the paving, (pictured).

My own conclusion is due to sub-surface water, given the direction of gradient, as other paving stones around the garden have not suffered similar effects.

The paving was laid over 150mm of MOT, using a full 6:1 mortar bed, finished using HD sealer.

All thoughts are welcome, anyone agree that this is due to water, can it be removed, will it get worse?

Wish I could post some photos, but just cant work out how to do it?
Image tab asks for a URL?
Cheers Andy

[geordieboy]

Andy, go to the noticeboard and you will find How to upload photies
Cheers
Will

[Tony McC]

Or send them to me and I can upload on your behalf.....

[Tony McC]

The images....

[xssc32x]

Hi, have exactly the same issue on my Digby stone forest green slabs. Have you found out how to remove staining?
Cheers
Si

[andymoz]

Still scratching my head over this one Si,

Clarification would be great, but subsurface water is my best guess?

Hoping someone has experience of the cause and how to remove?

Obvs wanting to stay away from chemicals, and with the paving down nearly year, intended to carefully run a wire brush across the worst of it, prior to pressure washing and resealing.

Thoughts appreciated?

Andy

[Tony McC]

I think some of the staining is moisture contaminating the sealant. Impossible to be certain without feeling it and seeing it for myself, but those white streaks are archetypical of moisture contamination.

I also suspect there is a dash of efflorescence, which has been more of a problem this spring/summer than usual. That probably arises from the bedding mortar.

If you use an appropriate sealant stripper that would verify whether it really is an issue with moisture. FAQ - When Sealants Go Wreong

[andymoz]

Cheers for the reply, the surface feels smooth, I’ve mechanically scraped into the stone, and it seems to be pigmented within the stone rather than staining sitting under the sealer.

Interestingly, staining is not present in areas; back butted using SBR slurry mix!

Unfortunately the Mira strip / clean products recommended at the ‘’When sealants go wrong page’ are no longer available. Therefore intend to use one of the following products to give it a really good clean, and prior to resealing.

https://www.ebay.co.uk/itm....45cfWbC

https://www.pureadhesion.co.uk/ecoprot....re.html

Cheers Andy

[Tony McC]

I'll wait for our own resident cleaning expert to comment on those products, but I'm surprised the Mira stuff is no longer on sale.

Due to the almost imminent launch of the new website, I can't update anything at all on the current site, but I'll make a note to look into this and update the new site as soon as I possible can with current information.

[andymoz]

Tony that's great, would rather wait and use a product that comes recommended.

For info, it looks like the Mira stuff has re-branded to 'Miracle Sealants Tile and Stone Cleaner', also unavailable in the UK.

Cheers Andy

[RAPressureWashing]

I don't know either of those 2 products mentioned above, so can't really comment, as for Mira Strip, yes the Americans (Miracle) have stopped shipping it abroad and was told they have stopped making it full stop, as everything is going over to water based strippers?, which is a shame as it was a really good solvent stripper, the nearest thing to Mira-Strip is Lithofins Wax-Off, a solvent and will remove some coatings, but as always won't get all of them. There are other strippers I use, mainly from Tensid, but I'd really need to know what it is that needs to be removed?, before advising, some of them have very long dwell times & you also need heat/steam to assist the removal.

[andymoz]

Taking good advice from this website, I applied 2 coats of ADSEAL Heavy Duty Sealer last summer, using a roller, it applied very well leaving a linear finish.

Ill take advise, but to be honest, if it wasn't for the strange staining (Pictured above), I'd be happy to pressure wash and reseal.

Not sure whether anything can be done about the staining, but re-sealing may go some way to help blend it in? I'm also seeing green growth, visible across the resin jointing, probably another indication that its time to re-seal. I'm sticking with the HD stuff as I have 1/2 a tin remaining from last year.

Question: Is it best practice to strip and re-seal or pressure wash using a cleaner ahead of resealing?

Many thanks

[RAPressureWashing]

Okay I'll give you my view on this, seeing as it is what I do for a living, the Adseal, totally the wrong sealer for your paving, more of a commercial usage, I'd do a full strip of the sealer to remove everything and you' most probably find the white staining will go, as it looks like moisture trapped under that sealer, then once completely dry apply a good quality colour enhancing impregnating sealer.

[gavinruane]

I have just completed a 100m2 kandla grey sandstone patio....in the morning the stains are prominent...on a warm day they go away...it is not sealed...i did not put a slurry on the back...anybody know how i can solve this problem please ??

[gavinruane]

Sorry i forgot to say...these slabs are very very thin..i was thinking of taking them up ..sealing the underside and then relaying them ??