How to lay Indian sandstone paving

Video by Marshalls. This guide is based on the tutorial “How To Lay Indian Sandstone Paving Slabs” from the Marshalls Gardens and Driveways YouTube channel. Marshalls are the UK’s leading natural stone paving manufacturer and their instruction videos are precise and practical. The section on wetting slabs before laying is particularly worth paying attention to — it is the step most people skip and then regret.

1. Plan the layout and order your materials

Sketch the area to scale and work out the slab layout before you order anything. Most Indian sandstone comes in mixed packs of four sizes, and planning the pattern means you can calculate how many full slabs, how many cuts, and how much wastage to allow. Add around 10% for cuts and breakages.

Check the area for drainage. The finished patio needs a fall of at least 1 in 80 away from the house — roughly 12 mm per metre. Plan this in at the setting-out stage, not as an afterthought once the slabs are down.

2. Excavate and prepare the ground

Dig out the area to a total depth of around 200 mm below the finished paving level: roughly 100 mm for Type 1 sub-base, 25–40 mm for the mortar bed, and the thickness of the slabs (typically 18–25 mm for Indian sandstone). Add a little extra if the existing ground is soft.

Remove all topsoil and organic material. Roots left in place will rot and cause settlement. If the ground is particularly soft or waterlogged, consider a geotextile membrane at the bottom of the excavation before the sub-base goes in.

3. Compact the Type 1 sub-base

Spread and compact at least 100 mm of Type 1 MOT aggregate (crushed stone) across the full area. Hire a vibrating plate compactor if you have a large area to do — it will compact the material properly in a way that hand tamping cannot. Work in layers of around 50 mm if you are building up significant depth.

Once compacted, the sub-base should feel solid underfoot with no give at all. Any movement at this stage will translate directly into rocking slabs later. A laser level or long straightedge is useful here to check the gradient is consistent across the whole area.

4. Wet the slabs before laying

This step gets missed constantly, and it causes no end of problems. Indian sandstone is highly absorbent. If you lay it dry onto a wet mortar bed, the slab will draw moisture out of the mortar too quickly, leading to a weak bond and eventual loosening.

Wet the backs of the slabs thoroughly an hour or two before laying, then again immediately before they go down. You want the slab damp but not dripping. It is one of those steps that takes thirty seconds and saves hours of relaying later.

5. Lay on a full mortar bed

Mix a 5:1 sharp sand to cement mortar, or use a proprietary paving mortar. The consistency should be firm enough to hold a footprint but not crumbly — sometimes described as a “biscuit dough” mix. Avoid wet, sloppy mortar: it causes the slab to sink and slump unevenly.

Lay a full bed rather than five-spot dabs. Dabs leave voids beneath the slab that fill with water, freeze in winter, and crack the stone. A full bed of 25–40 mm supports the slab evenly across its whole surface. Screed the mortar out flat for each slab, then lower the stone onto it.

6. Set levels and check the drainage fall

Use a rubber mallet and a long spirit level to bed each slab to the correct level and fall. Check across adjacent slabs as well as along the run. Indian sandstone is a natural material and slabs vary in thickness, so you will need to adjust the mortar bed depth for each one individually.

Use plastic tile spacers or short pieces of timber for consistent joint width. Standard joint width for Indian sandstone is around 10–15 mm. Leave the slabs to cure for at least 24 hours before walking on them, and ideally 48 hours before pointing.

7. Point the joints

Once the mortar bed has cured, brush and blow out any loose debris from the joints. Mix a pointing mortar at around 3:1 sharp sand to cement, slightly drier than the bedding mix. Press it firmly into the joints using a pointing tool or a gloved hand, making sure there are no voids.

Brush off any surplus before it dries. Indian sandstone stains easily from cement, so keep a damp sponge handy and wipe the slab faces as you go. Brush-in jointing mortars are quicker and easier for larger areas, but require careful surface cleaning before the compound sets hard.

8. Seal and maintain

Sealing Indian sandstone is optional but recommended. A good natural stone sealer repels water, reduces algae and moss growth, and makes the surface easier to clean. Apply it at least two weeks after laying, once the pointing mortar has fully cured.

After that, an annual pressure wash and a re-seal every two or three years keeps it looking good. Indian sandstone does not need a great deal of attention to stay presentable — it is one of the reasons it is so popular in UK gardens.

When to call a handyman

Indian sandstone paving is perfectly achievable as a DIY project for smaller areas. For a full patio, the physical work is significant — digging, moving heavy slabs, and mixing mortar is a two-person job at least. Call Richard if the ground slopes awkwardly, if there are drainage concerns near the house, or if you want the job done in a day or two rather than a long weekend.