Indian Stone / Jointing Compound Staining

Question

Good morning.

I hope that you are well.

I am looking for a bit of advice please.

We had some Indian Stone paving laid in mid-November 2023. We haven't actually used it, as such yet, as the landscaping work is still ongoing.

We have noticed discolouration of the jointing compound / potentially the flags themselves, around some of the flags.

As far as we are aware, the tradesmen working on the project have not used any cleaner on the flags. It has just had the occasional jet wash with water throughout the project.

Does anyone have any idea as to what the build up / discolouration is please and any advice about how I can go about removing it? The issue is only present around certain flags, not all of them.

The two videos here highlight the issue better than I can describe it :-

https://youtu.be/dmBaGrDwe0o

https://youtu.be/KhIEw1UHGvA

The stone used is brand new.

Any advice on the root cause or solution to this problem would be much appreciated.

Many thanks
Jimmy

Ricardo · Accepted Answer

Hi Jimmy, I can almost guarantee that it is the salts coming through. Just dont seal it until the salts have gone through completely. Process can take up to 2 years from my experience. May have something to do with using the slurry primer on cold temperatures. I would ask them about that maybe. Good luck.

Marian · Answer

A combination of the freezing temperatures and wet weather can leave even the hardiest outdoor areas looking a little neglected and in need of some TLC. Cracked grouting leaves gaps between stones – where weeds will flourish come spring – and the overall look can be very messy.

Need to repoint the patio, First take off the existing joints.

After Use a good quality jointing compound. Once all your joints are full of compound, sweep aside the excess product and begin to strike it in.

Mac · Answer

Good morning, Jimmy,

I hope the below helps?

Possible Causes of Discoloration:
Efflorescence: This is a common issue with natural stone and jointing compounds. Efflorescence occurs when water rises through the stone and mortar, carrying salts to the surface, which then leave a white or cloudy deposit. This is more likely to happen in the months following installation, especially in colder, damper weather.

Moisture Trapped Under the Stone:
If the paving was laid on a wet mortar bed or if water is sitting underneath the slabs (due to poor drainage), it can cause uneven drying and discoloration. This might lead to patches of darker stone or discolored jointing compound.

Jet Washing:
While it sounds like no harsh chemicals were used, jet washing can sometimes push dirt or jointing material into the pores of the stone, leading to discoloration around certain flags. Indian sandstone is porous, so any debris or jointing material residue could be absorbed and cause staining.

Wait It Out (Efflorescence):
If efflorescence is the cause, it will often disappear on its own after a few months as the salts are washed away by rain and weathering. You can also use an efflorescence cleaner specifically designed for natural stone. Make sure to follow the manufacturer’s instructions carefully.

Stone Cleaner:
You could try a pH-neutral stone cleaner designed for Indian sandstone. Avoid using acidic or harsh cleaners that might damage the stone or cause further discoloration. Apply the cleaner as directed, then rinse with clean water.

Drying Time:
Ensure that the area around the stone is well-drained and that the base material isn’t holding excess moisture. If the issue is due to trapped moisture, improving drainage could help the stone dry out evenly over time.

Next Steps:
Try a small test area with a cleaner designed for natural stone, or even just a thorough rinse and scrub with water, before applying any products to a larger section.
Monitor the issue over time, as some discoloration could be temporary, especially if it's due to efflorescence.
Since the issue is localized to specific areas, it seems less likely that it's a major installation error, but if the problem persists, it might be worth having the tradesmen check the base and drainage underneath.

Best,
Mac
eHealthyHomes

Robert · Answer

Totally agree with the last answer so to be honest  the flags are so poures maybe a different  type of grout  could of been used  but unless you want to drag it all out and spend time and money   the best option would be wait it out

Wayne · Answer

Well likely be the salt coming up. Just don't seal it until the salt have dissolved completely.

Michael · Answer

It would be the salt from the stone. It will take time to bleed through

Samuel · Answer

You can sue black spot which will clean the slabs off perfectly and then seal the slabs which will leave a new drag look to them

David · Answer

That is easy over time this should happen, but i am not sure how long this work has been finshed , it looked like they have used normal filler like concrete , you need to get patio cleraner and the patio washer that connects to a jet wash.
then fill with proper pater snd whcih will solidfy over time..iokay

Peter · Answer

The jointing compound could be discoloured as water might not be leaving the joints which could cause an ideal environment for mold/algae build up it would be more noticeable on light colours,  same with the stone, worse in shaded areas or north facing gardens a good spray and leave product should work.

Christopher · Answer

Efflorescence Remover will remove any staining and cement residue, will also remove and salt that comes up and sits ontop of the flags this will remove and white spots and colour

Indian Stone / Jointing Compound Staining

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