How to lay Indian sandstone slabs?

This is not being laid correctly please get them to stop it should be laid with a hardcore subbase to start and then laid on sharp sand and cement wet mix and all slabs should be painted with a slurry primer or they will come loose. Guaranteed ive been laying sandstone for over 10 years and unless they are laid correctly you will have nothing but trouble

Based on your description, the landscaper is not following standard installation practices for Kandla Indian Sandstone. Laying slabs on top of stone/sand without a full cement mortar bed will lead to serious issues, including movement, sinking, and potential cracking over time.

From what you’ve described, this doesn’t sound like a proper installation for Indian sandstone. Normally, slabs should be laid on a solid, compacted sub-base (like MOT Type 1) and then bedded on a full mortar bed (sand and cement) so they are fully supported and bonded in place, especially as sandstone varies in thickness and needs adjusting individually to achieve a level finish. Simply laying slabs on loose stones without a mortar bed is not standard practice and can lead to movement, rocking slabs, and joint failure over time, as jointing compound is only for finishing and does not hold the slabs in place. Based on this, there is a risk the patio could become uneven and unstable in the future, so it would be reasonable to clarify whether a full mortar bed is being used before the work progresses further.

We personally lay flags on a full bed of mortar (grit sand and cement) and also apply SBR to the back of flags to help with bonding. We also use a resin jointing compound to infill gaps between flags rather than mortar as that will crack with movement

Based on the details you’ve provided, your concerns are absolutely valid. The method being described—laying Indian sandstone directly onto a base of loose stones without a mortar bed—is incorrect and will almost certainly lead to long-term issues.

all slabs should be laid with a full bed of cement and the back of the slab should also be primered

Short answer: This is not standard best practice for Indian sandstone paving – your concerns about movement and long-term issues are valid.

What should have been done

There are two main standard methods for laying sandstone slabs:

1. Mortar bed: Slabs are laid on a full bed of sharp sand and cement (typically 4:1 mix), which levels uneven thicknesses and bonds them securely to the base.

2. Flexible paving system: Slabs sit on a layer of compacted aggregate, then a bed of sharp sand or specialist paving bedding material – not loose stones – with jointing compound used for gaps.

Problems with the current approach

- No stable base: Loose stones won’t provide consistent support, so uneven slab thicknesses will lead to wobbling and settling over time.

- No bonding: Without a mortar bed or properly compacted bedding layer, slabs can shift, lift, or crack as they’re walked on or exposed to weather/moisture.

- Jointing issues: Pavement joint mortar is designed for filling gaps between slabs, not to hold them in place or compensate for an unstable base.

There should be a mortar laid underneath to level the slabs. Using a long spirit level to get the slabs even,should keep the stones from being too uneven.

Hi there, yes this all seems very odd to me. Every patio we've laid the process is as follows. We dig out to between 150mm & 160mm followed by then fill excavated area with 100mm of sub base (MOT type 1) fully compacted with a sprinkling of water to help with compaction. This then leaves 40 to 50mm depth for a full bed of mortar to lay your slabs on. I always lay on a full bed to prevent rocking slabs. Followed by pointing in of the customers choice

He needs to compact the aggregate at least five times with the compactor
And lay the Indian sandstone you need a sharpsand and cements mix that the Slab should be bedded in to
a level to allow water to flow off
And then to re-point the slabs once laid
Either with a motor mix or joint compound

All slabs must be laid on at least 3 to 4 inch maybe someplace 5 inch of conquering and the foundation should be approximately depending on the area dug out to appropriate that supply and lay three foundation type one and all slabs should be laid with a PVA binder to make them stick to the cement And the grouting should be the last thing to be done

Your landscaper's method is incorrect and will lead to future problems; Indian sandstone needs to be laid on a full, solid bed of mortar (sharp sand and cement) with a slurry primer on the back of each slab for adhesion, not just on grit/stones with pointing as the sole fix, especially with varying slab thicknesses; this "spot bedding" or just using jointing mortar for support causes movement, unevenness, and potential cracking, requiring a proper re-lay on a full mortar bed to ensure stability and longevity.

Hello
Regarding the sand stone patio installation
To have a proper patio installed
The base will have to be minimum
•100 mm of hard core base
compacted very well
Install a drine sistem aco drine /perforeted pipe on end of the patio
Install of the slabs
•Sand stone slabs are 20 mm thick
So must be laying down on wet mortar
4/1
•4 parts sharp sand
•1 part cement
•With mortar plaster for a proper mixture

•All slabs installed have to be installed with a primer slurry
And the Joints can be filled with

•Joints mortar
•Brush in stuff suitable for sand stone /
Sika grout / easy Joint Pro joint

And also is recommended to use a paving sealer after 6 months of installation
And after that maintenance will be
Indicated 1 power wash a year
To keep it nice & smooth
As we know that
Sand Stone is a natural stone
wick absorb water and goes green and will make the patio to look old and

Maintenance will be recommend 1 a year

Power wash
Refilling joints if required

That way you can enjoy a patio 10 years +

Chris

You need to put a MOT base down Wacker it then lla layer of sand.

Sand and cent mix is required over the whole over the area to be slabbed not just spotting.
And also prime the back of the slabs with a sandstone slab primer

Yes quite right!!! The way this landscaper has performed is in no way acceptable and is no way to lay sandstone slabs. Laying them in this fashion will end up with moving slabs when walked over and in turn the grouting will just crumble in a matter of no time at all. The landscaper clearly to me does not know what he is doing.

It sounds like you have some real concerns about the way the landscaper has installed those sandstone slabs. Ideally, there should be a solid base, like compacted gravel or sand, laid down before the slabs go on. Using cement or some kind of adhesive under the slabs is also standard practice to keep them secure and prevent shifting.

The fact that you’re seeing different thicknesses among the slabs and some being uneven is definitely a red flag. That could lead to problems later on, like cracks or movement, which nobody wants.

If you're feeling unsure about speaking up, maybe you could do a bit of research on proper installation techniques. It might help build your confidence to ask him about his methods. A good landscaper should be open to discussing your concerns and explaining what he’s done. If you're still uncomfortable, getting a second opinion from another professional could also give you peace of mind. It's important to feel confident in the work being done.

To lay Indian sandstone, first prepare a stable, compacted sub-base. Apply a full bed of mortar to the sub-base, ensuring a consistent thickness. Apply a slurry primer to the back of each sandstone slab to improve adhesion. Lay the slabs onto the wet mortar, tapping them into place with a rubber mallet to ensure they are level and create a slight fall for drainage. Maintain uniform gaps of 8-10mm between slabs and then compact the joints with a suitable mortar. Allow at least 24 hours for the mortar to set before walking on the patio.

They won’t end up becoming an issue they already are an issue. He has layed the slabs straight on top of stones them stones are whacked down and used as a base for cement which you then lay your slabs on. At the moment you haven’t got anything actually bedding the slabs to t ground, if you was to go to the corner of any of the slabs and try to lift them they would lift straight up. The grout they have used isn’t actually doing anything other than filling the gaps in between the tiles they need to be lifted up then relayed on top of a cement base. Once the cement goes hard and you can walk on it that’s when you grout it that’s always the last thing to do with patios.

What we would do and what he should have done was a dry mix of sand and cement laid that down first the have a wet slurry of cement to brush along the bottom of the sand stone then lay them more often to not you can tamper them in all level regardless of thickness this also allows for less wastage on grouting

Firstly the gound should of been dug to the correct depths,continuing to check. Realistically they should be 2 course of brick below damp level(150mm).
He should allow 18mm to 22mm which is the variation in Indian stone packs if they have supplied none calibrated packs( usually cheaper)50mm to 75mm for a wet cement bed and a minimum of 150mm type 1 stone. Which needs to compacted using a whacker plate. Depending on preference you can seal the back of the slabs with a primer of choice. Gaps on joints should be no more than 20mm wide. With a depth of 25mm any shallower and the resin joints will blow out after a short period.Also Depending on ground level my require a acoe chanel. But indian stone is very porous so absorbs alot.

Indian sandstone needs a slurry sealant mix painted onto the back and then laid of full beds of cement

They are supposed to be laid on a wet full mortar bed.
You will definitely be having issues in the near future

You want a full bed under the slabs of wet mix containing either 6mm to dust or concrete sand and cement.
Although Indian stone is a natural product and thickness may vary.

Need in a well prepared Sub-Base MOT. Lay with cement and sand mix and putting slurry primer at the back of the slab, like that you will never have problems

Head core need wacking then layed on sand/cement mix this is all wrong the way he is laying it