Quick Answer: How Do You Lay Indian Sandstone Paving?
Indian sandstone paving should normally be laid on a properly compacted MOT Type 1 sub-base, with the slabs fixed on a full mortar bed rather than spot bedding. The patio should be planned with a fall away from the house, usually around 1:80 to 1:100, so surface water can drain correctly in UK weather conditions.
The key stages are setting out the patio, checking finished levels, excavating to the correct depth, compacting the sub-base, preparing a suitable mortar bed, laying and levelling the slabs, keeping joints consistent, cleaning as you work, then pointing or jointing the patio once the paving is firm enough. Smooth sandstone and dense slabs may also require a suitable bonding slurry or SBR primer on the underside before laying.
1. Planning and Setting Out
Before you start digging or ordering materials, take time to plan the project properly. Visualise the finished patio or pathway and consider the shape, direction of fall, access points, door thresholds, garden walls, steps, drainage channels, curved edges and any brick or sett borders.
Mark the area with pegs, string lines or spray paint. Check that the proposed patio size works with the house and garden rather than simply filling the available space. A patio should look connected to the property, not added as an afterthought.
Once the area is marked out, calculate the square meterage and allow extra material for cuts, selection, damage and natural stone variation. Many patio projects allow around 10% extra, but more may be needed for diagonal cuts, curved edges, complicated steps or mixed-size layouts.
2. Choosing the Right Indian Sandstone
Choosing the right paving is part of the installation process. The finish, thickness, slab size and edge style all affect how the patio should be laid.
Indian sandstone paving is available in riven, smooth and sawn finishes. Riven sandstone is split along natural bedding planes and has a traditional textured surface. Smooth or sawn sandstone has a flatter finish and usually requires more careful laying because the surface, edges and levels are more visually exacting.
Popular colours such as Kandla Grey sandstone, Raj Green sandstone and Autumn Brown sandstone should be blended before laying because natural colour movement is part of real sandstone. Do not lay one full crate at a time without checking the overall colour spread.
3. Working Out Your Levels and Falls
Correct levels are essential for both appearance and drainage. Start by identifying fixed reference points such as house walls, door thresholds, existing paving, drains, steps, paths and garden edges.
As a general rule, paving around a house should finish at least 150 mm below the damp proof course unless a properly designed drainage detail has been provided. The patio should also fall away from the building so water does not sit against the wall or flow towards the house.
For many domestic patios, a fall of around 1:80 to 1:100 is commonly used. In practical terms, this means roughly 10 mm to 12.5 mm of fall per metre. The exact fall depends on the site, paving finish, drainage arrangement and installer judgement.
Use string lines, pegs and a long spirit level to establish the finished level before excavation begins. It is much easier to correct levels at the planning stage than after the sub-base has been compacted or slabs have been fixed.
4. Drainage Planning for UK Weather
Drainage is especially important in the UK because patios are exposed to regular rain, damp winters, shaded areas, algae growth and occasional freeze-thaw conditions. Indian sandstone is a natural sedimentary stone, so it should not be laid in a way that allows water to sit beneath the slabs or against the house.
The patio should be designed so surface water runs away from buildings and towards a suitable drainage point, garden area or linear drain. Flat patios may look neat at first, but standing water can encourage algae, staining, frost damage, joint failure and long-term movement.
Drainage should be considered before laying begins. If water has nowhere to go, the paving material alone cannot solve the problem. The correct fall, sub-base, mortar bed and jointing all work together to keep the patio stable and usable.
5. Excavation Depths
Excavation depth depends on the paving thickness, mortar bed, sub-base depth and the existing ground conditions. For a typical pedestrian patio using Indian sandstone slabs, a practical build-up may include around 100 mm compacted MOT Type 1 sub-base, 30 mm to 40 mm mortar bed and the paving slab thickness.
If the sandstone is around 22 mm thick and the mortar bed is around 35 mm, the total excavation depth is often around 155 mm to 165 mm below the finished paving level. This is only a guide and should be adjusted to suit the site.
Excavation should remove loose soil, roots, soft spots and unstable material. The base should be firm and consistent before sub-base material is placed. Soft or wet ground may need additional excavation, a stabilisation layer or geotextile membrane depending on the condition of the site.
6. Sub-Base Preparation
A strong sub-base is one of the most important parts of a sandstone patio. MOT Type 1 compactable aggregate is commonly used because its angular particles lock together when compacted, creating a stable foundation for the mortar bed and slabs.
| Project Type | Typical Sub-Base Depth | Notes |
|---|---|---|
| Pedestrian patio or garden path | Around 100 mm compacted MOT Type 1 | Suitable for most domestic foot traffic when ground conditions are firm |
| Heavier use patio or poor ground | 100 mm to 150 mm or more | Depth may need increasing where ground is soft, wet or unstable |
| Driveway or vehicle area | Usually 150 mm or more, subject to design | Indian sandstone slabs are not automatically suitable for driveways; specification must be checked carefully |
| Soft or unstable ground | Site-dependent | A geotextile membrane or deeper stabilised construction may be required |
The sub-base should be spread in layers and compacted thoroughly with a whacker plate. Do not simply rake loose aggregate into place and lay over it. Poor compaction can lead to settlement, cracked joints, rocking slabs and low spots where water collects.
Use string lines and pegs to control the level of the sub-base. The surface should follow the planned fall of the patio, leaving enough depth for the mortar bed and paving slabs.
7. Preparing Slabs and Materials Before Laying
Before mixing mortar, position the sandstone slabs and materials close to the working area. If you are using a patio pack, sort slabs by size so the laying pattern can be followed properly. If you are using natural sandstone from more than one crate, open several packs and blend the slabs before laying.
Check for light, dark and strongly marked slabs before fixing them permanently. This is especially important with Raj Green, Autumn Brown, Rippon Buff and other naturally varied sandstone colours. Even Kandla Grey can include silver, blue-grey, darker grey and occasional buff movement.
Keep water, a hand brush and cleaning tools nearby. Cement and mortar marks should be removed immediately while fresh. Once cement staining has set on sandstone, it can be difficult to remove without damaging the appearance of the stone.
8. Mortar Mix and Bed Thickness
The mortar bed should support the whole underside of each slab. Indian sandstone should normally be laid on a full mortar bed, not on small spots or dabs of mortar.
A common mortar mix for laying sandstone is 1 part cement to 4 or 5 parts sharp sand. Some installers add a small amount of soft sand to improve workability and stickiness. The mix should be moist and workable, similar to thick bricklaying mortar, not powdery and dry.
A mortar bed of around 30 mm to 40 mm is often used for patio slabs. A very thin bed may not give enough support or adjustment. A very thick bed can be difficult to control and may increase the risk of movement if not properly compacted and supported.
The exact mortar bed should suit the slab thickness, sub-base level and site conditions. The installer should bed each slab firmly so there are no voids underneath.
9. SBR Slurry and Bonding Primer
For smooth sandstone, sawn sandstone, dense slabs or projects where stronger adhesion is required, a suitable bonding slurry or SBR primer is often used on the underside of the slab before it is placed into the mortar bed.
This helps improve the bond between the stone and the mortar. It is especially important where the underside of the stone is smoother or less absorbent than traditional riven sandstone. The primer should be applied according to the product manufacturer's instructions and the slab should usually be laid while the slurry is still wet and active.
Do not assume that all sandstone can be laid successfully without considering bond strength. A slab that is poorly bonded may sound hollow, move over time or become more vulnerable to frost and water-related problems.
10. Laying the First Slabs
The first few slabs are critical because they establish the level, fall, joint direction and overall alignment of the patio. Take time at this stage. If the starting line is wrong, the error will often become more obvious as the work continues.
Place the first slab onto a full mortar bed and tap it down carefully with a rubber mallet. Check the level, fall and alignment with a long spirit level and string line. The slab should be fully supported underneath, with no rocking and no gaps beneath the stone.
Keep checking that water will run in the intended direction. A patio can look flat to the eye but still fail if the fall is wrong.
11. Maintaining Joint Consistency
Indian sandstone joints need careful control, especially when using riven slabs with hand-dressed edges. Natural stone is not always as exact as porcelain, so the installer must allow for small variations in slab size and edge character.
As a general guide, joints of around 10 mm are commonly used for Indian sandstone paving, although the exact width depends on the product, edge type and laying pattern. Sawn stone may allow tighter and more regular joints, while rustic riven paving usually needs a little more tolerance.
Dry-laying a small area before fixing can help the installer understand the joint width and pattern. This is particularly useful with mixed-size patio packs.
12. Keeping Lines Straight
Straight lines are important even on a traditional patio. Use string lines, a long spirit level and fixed reference points to keep the pattern running correctly.
When laying against a house, wall or straight edge, check that the paving sits square with the building where appropriate. On older properties, walls may not be perfectly straight, so the installer may need to make a judgement about which line should visually control the patio.
Do not rely only on the previous slab. Small errors can build up across a patio and create wavy joint lines, especially with mixed-size paving.
13. Capping Long Joints in Patio Packs
When laying mixed-size Indian sandstone patio packs, avoid creating long continuous joints that run too far through the patio. These long joints can make the pattern look weak and less natural.
The installer should cap long joints by placing another slab across the line, breaking up the pattern and keeping the layout balanced. This is one reason patio packs should be planned carefully rather than laid randomly without checking the pattern.
A good random patio pattern is controlled. It should look natural, but it should not be careless.
14. Keeping the Project Clean
Cleanliness is essential when laying Indian sandstone. Cement, mortar and slurry marks can stain the surface if they are left to dry.
Keep a bucket of clean water and a hand brush close to the working area. Remove splashes immediately while they are still fresh. Do not smear cement over the stone surface, and do not allow mortar residue to dry into the riven texture.
Extra care is needed with lighter colours such as Mint Fossil, Rippon Buff and pale buff sandstone because staining may be more visible. Smooth sandstone can also show marks more clearly than traditional riven paving.
15. Pointing and Jointing Options
Once the slabs have been laid and the mortar bed has had enough time to firm up, the joints can be filled. Jointing should not be rushed. If slabs move during pointing, the finished patio can suffer from weak joints, staining or uneven lines.
There are several ways to joint Indian sandstone:
| Jointing Method | Best for | Main Consideration |
|---|---|---|
| Traditional wet mortar pointing | Professional installation and traditional patios | Strong and durable when done properly, but can stain sandstone if applied carelessly |
| Semi-dry mortar mix | Experienced installers | Needs the right moisture level and careful compaction into the joints |
| Brush-in jointing compound | DIY-friendly patios and simpler projects | Easier to use, but the joint depth, weather and product instructions must be followed |
| Resin-based jointing compound | Projects needing a cleaner modern jointing system | Usually more expensive; surface cleaning and correct application are important |
A traditional mortar pointing mix may use 1 part cement to around 3 parts suitable plastering sand, mixed to a controlled consistency. It should be compacted properly into the joints and finished neatly below the top surface of the paving.
Modern brush-in and resin-based jointing compounds can be more convenient for DIY users, but they must still be used correctly. The joints need adequate depth, the slabs should be stable, and the instructions for wetting, brushing, compacting and curing should be followed carefully.
For more detail, read our guide on how to point or repoint Indian sandstone patio.
16. Sealing Indian Sandstone After Laying
Sealing Indian sandstone is optional. It is not a substitute for good installation, correct drainage or regular cleaning. However, it can help reduce staining risk in some situations, especially on outdoor dining areas, BBQ zones, shaded patios, smooth sandstone and lighter colours.
A sealer may change the appearance of sandstone, often making the colour appear deeper or richer. It should always be tested first on a spare slab or small hidden area before being applied across the whole patio.
Newly laid paving should usually be allowed to dry and settle before sealing, and the surface must be clean. Trapped moisture, mortar staining or poor preparation can cause problems if a sealer is applied too early or incorrectly.
For more detail, read our guide on whether it is worth sealing Indian sandstone.
Common Mistakes to Avoid
Spot Bedding the Slabs
Spot bedding means placing small dabs of mortar under the slab instead of a full supporting bed. This should be avoided for Indian sandstone patios because it can leave hollow areas, encourage water pockets, increase the risk of movement and make the paving more vulnerable to cracking or frost-related problems.
Ignoring the Fall
A patio that looks level may still fail if water cannot drain away. Plan the fall before laying starts and check it throughout the job. Standing water is one of the most common causes of long-term patio problems.
Laying One Pack at a Time
Indian sandstone should be blended from several packs where possible. Laying one pack at a time can group colours unevenly, making natural variation look like a mismatch.
Pointing Too Soon
If jointing is carried out before the slabs are stable, movement can disturb the lines and weaken the finished joints. Allow the mortar bed to firm up properly before pointing.
Leaving Cement Stains to Dry
Mortar and cement marks should be removed immediately. Once set, they can be difficult to clean from riven sandstone without affecting the surface.
Skipping Ground Stabilisation Where Needed
On soft or unstable ground, a simple shallow sub-base may not be enough. Additional excavation, geotextile membrane, deeper Type 1 or site-specific stabilisation may be needed.
Final Recommendation
Laying Indian sandstone correctly is a practical trade process, not just a matter of placing slabs on the ground. The long-term result depends on preparation, levels, drainage, sub-base compaction, full mortar bedding, slab blending, careful jointing and good site cleanliness.
For DIY users, the most important points are to plan the fall, prepare a strong base, avoid spot bedding, keep the project clean and understand that natural sandstone needs blending before laying. For homeowners using an installer, this guide can help you check whether the work is being approached properly.
You can also view our laying patterns for a patio and our paving expert guide video for additional visual guidance.
How to Lay Indian Sandstone Paving: Frequently Asked Questions
How deep should I dig for an Indian sandstone patio?
For a typical pedestrian patio, excavation is often around 155 mm to 165 mm below the finished paving level. This allows for around 100 mm compacted MOT Type 1, a 30 mm to 40 mm mortar bed and the sandstone slab thickness. The exact depth depends on the site, ground conditions and product specification.
What is the correct mortar mix for laying Indian sandstone?
A common mortar mix for laying Indian sandstone is 1 part cement to 4 or 5 parts sharp sand. Some installers add a small amount of soft sand to improve workability. The mix should be moist and workable, similar to thick bricklaying mortar, and the slabs should be laid on a full mortar bed.
How wide should the joints be between Indian sandstone slabs?
For many riven Indian sandstone patios, joints of around 10 mm are commonly used. The exact width depends on the slab finish, edge type and laying pattern. Sawn sandstone may allow tighter joints, while rustic hand-dressed slabs usually need more tolerance.
Can I lay Indian sandstone on sand rather than mortar?
Indian sandstone patio slabs should normally be laid on a full mortar bed over a compacted sub-base, not loose sand. A mortar bed gives better support, helps control levels and reduces the risk of movement, rocking slabs and water-related problems.
How long before I can walk on freshly laid Indian sandstone?
The safe waiting time depends on weather, mortar mix and site conditions. As a general principle, avoid walking on freshly laid sandstone until the mortar bed has firmed up properly. Heavy use, furniture and jointing should not be rushed.
Do I need to seal Indian sandstone after laying it?
Sealing is optional. It may help reduce staining in outdoor dining areas, shaded gardens, BBQ zones, smooth sandstone and lighter colours. However, sealing is not a replacement for correct installation, drainage or cleaning, and it should always be tested first because it may change the stone colour.
What fall should an Indian sandstone patio have for drainage?
Many domestic patios use a fall of around 1:80 to 1:100, usually running away from the house. This is roughly 10 mm to 12.5 mm per metre. The exact fall should suit the site, paving finish and drainage arrangement.
What is spot bedding and why should I avoid it?
Spot bedding means laying slabs on small dabs of mortar instead of a full mortar bed. It should be avoided because it can leave voids under the slabs, create hollow spots, trap water, cause movement and increase the risk of cracking or frost-related damage.
