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Landscape Gardening

Help please !!! how to remove rust stains from silver/grey indian sandstone

hi, following on from problems with my landscapers regarding laying our new stone patio with dot and dab method, they have now re-laid it all (approx 100 sqm) with full bed method (as advised by experts here on my builder).

When they re-laid the slabs using full bed of mortar, they stained the silver/grey pavers (with heavy mortar). Yesterday, they did a power wash and then used diluted hydrochloric acid with water to remove mortar stains. They scrubbed the pavers with wire brush and again did a power wash just with water.
After all of this, stone pavers look like brand new and we were really pleased.

woke up this morning to find out that many slabs look rusty ;(
what can we do to eliminate the rust marks from so many slabs?? we are really worried and stressed out about all of this as this has cost us a fortune and doesn't look right :(

what can i do now to remove these rust stains from our new patio. landscapers are coming on Monday for jointing the slabs..Have called them in the morning and they say it will all weather out and that they will do another power wash (just with water) to make it better

Please advise... we are really stressed out.
thanks ..

3 Answers from MyBuilder Landscape Gardeners

Best Answer

Hi there,

Really sorry to hear about your experience thus far. Unfortunately right from the dot and dab start it seems that the team you have in have been slightly ill-advised as to best practice to put it lightly.

I’m sorry to say that Hydrochloric acid, albeit a great cleaning agent used correctly, is also a dangerous one when not.

When using on a highly porous surface such as sandstone it really should be used in its very minimum strength and for very short periods of time. The slabs should have been wet previously in order to reduce absorption and it should have been washed off thoroughly at the end.

Without seeing it I cannot assure you that the damage isn’t permanent but I would recommend using a good quality (acid-free) rust remover like PaveTuf Rust Remover.

If this doesn’t work then your last chance would be oxalic acid, as this is able to remove some rust staining.

Just ensure you test it on a discrete area before using it on the whole patio as the strengths can vary massively dependant on where it is sourced from and testing will cause you no harm regardless.

I sincerely hope this works for you otherwise I would be trying to claim through your home insurance and they will no doubt pursue the installer’s business insurance provider to recover the cost for their mistake.

All the best.


Answered 6th Jul 2019

Take up with supplier. This is there problem. It tells you I’m small print this can happen. We had same problem supplier had to replace


Answered 10th Jul 2019

If it’s a natural sandstone you need to allow time for the salts to rise out of the mortar and through the slabs. This should take about a month. Then one more jet wash and seal should prevent this ever happening again. The rust is probably due to doing it too early


Answered 6th Jul 2019

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