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Landscape Gardening

Spotting on indian stone patio


I've recently had a patio laid with indian stone. The builder supplied the stone and he told me he used the spot method to lay them. My garden slopes towards my house and after a week or so of being in place, the slabs have wet blobs on them, soaking up from underneath. I'm told this is because of the spot method and it shouldn't have been laid like that.

Is this right? The builder insists the spot method is ok and he has never had problems with it in 20 years. The damp spots aren't going away (had very dry weather lately). I'm not sure if it is a problem with the spot method or the quality of stone (which isn't the best, even to my untrained eye). He charged 780 just for the slabs (there's around 70 of them) and 200 for the sand etc.

5 Answers from MyBuilder Landscape Gardeners

Best Answer

Natural stone should be laid on a full bed of mortar.
SBR and cement slurry is also recommended
The slabs will pop in a short time if they are on spots.


Answered 14th Aug 2018

indian sandstone should never be spot laid. infact in my opinion and experience i would say that spot laying is a silly mistake from the past and everything now should be laid on a full bed. when i lay sandstone i have a sub-base than a concrete slurry ontop and than i lay my sandstone ontop of that as sandstone has had problems with sticking. and often the old sandstone wasnt calibrated at the back so after a few years the smaller slabs would pop off iv always used this method and have never had any problems. so thats a no.


Answered 14th Aug 2018

I ALWAYS spot lay slabs of any material, your builder should have painted slurry on to the rear of the slabs , which helps the slabs to stick and also prevents moisture coming through I would think in time the dots will fade, I would question the product not the tradesman


Answered 14th Aug 2018

Indian stone should never be spot laid. This is the reason you have the spots coming through, it will look worse when the flags get wet. Indian stone flags need to be laid onto a full mortar bed and the back of the flags primed with an SBR Cement slurry mix to ensure a good bond with good strength, this also prevents any spots showing like you currently have.


Answered 15th Aug 2018

I lay all natural stone slabs on a 50mm screed of mortar. You don’t want any voids under such thin slabs. In cold weather the damp freezes and ultimately cause slabs to move. They are highly porous so damp patches are from the moisture in mortar or even for water trapped underneath on the voids. Not good practice imo.


Answered 27th Aug 2018

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