Choosing patio paving and setts
Short answer: Indian sandstone is a popular, affordable natural stone for a patio. Granite and slate are denser and tougher, limestone stands up well to British weather and porcelain is the low-maintenance alternative. Concrete slabs and block paving are the other common choices, and printed concrete is poured and stamped on site by a contractor. Whatever stone you choose, lay it on a compacted sub-base and a full bed of mortar, never on spots, and order around 10% more than the area for cuts and sorting.
Updated
A well-laid stone patio should last until you decide to change it, and that comes down to the stone you pick, how it's cut and, above all, what it's laid on.
The main choices
| Material | Good for | Watch for |
|---|---|---|
| Indian sandstone | Riven, rustic patios at a sensible cost, in buffs, greys, browns and greens. Look for names such as Kandla Grey, Raj Green and Autumn Brown. | Colour varies from slab to slab. Sawn sandstone soaks up water and dirt more readily, so it's worth sealing. |
| Limestone | Low upkeep and stands up to British weather, in colours from yellow to grey and black. | Acid-based cleaners lighten it quickly, and it can lighten a little over time anyway. Seal sawn limestone. |
| Granite | One of the toughest paving stones, with a tight grain and even colour. Granite setts suit drives. | Harder to cut. It's so dense that the back of each piece needs a primer slurry to bond to the mortar. |
| Slate | A flat, dense surface that resists stains, for a contemporary look. | It's split, not sawn, so thickness varies, and like granite it needs a primer slurry. Colour varies, so see a sample. |
| Porcelain | Even colour, crisp edges and very little upkeep. It absorbs almost no water, so frost doesn't get in. | Use 20mm outdoor porcelain, never indoor tile. It must be primed and laid on a full mortar bed, and it needs the right cutting blades. Shade can differ between batches. |
Yorkstone, the traditional British sandstone, has centuries of use behind it in our climate, but it usually costs more than imported stone.
Concrete slabs, block paving and printed concrete
Three other surfaces are common in British gardens.
- Concrete slabs are made in a factory, in sizes from 300 by 300mm up to 900 by 600mm, and some are made to look like natural stone. Marshalls, which sells both, calls concrete the more affordable choice and says it needs little more than the occasional sweep and rinse.
- Concrete block paving is small blocks laid on a bed of sand inside an edging, so they lock together and spread the load. It's tough enough for a drive, and a section can be lifted and relaid with the same blocks. The sand joints need topping up and weeding from time to time.
- Printed concrete, also called pattern-imprinted or stamped concrete, isn't bought in packs. A contractor pours concrete on site, colours it and presses a pattern into it before it sets, so it can look like brick, cobbles or slate. With no joints, weeds have nowhere to grow, but installers recommend resealing every two to five years. It can crack if the base isn't prepared properly, and a cracked section is harder to repair than block paving.
The rest of this guide is about natural stone and porcelain.
Calibrated, hand-cut or sawn
Each word describes something different, so one slab can be several of them.
- Calibrated is about thickness. The back is machined flat so every slab is close to the same depth, most often 22mm, though some ranges are 18mm. It's quicker to lay because the mortar bed doesn't need adjusting slab by slab.
- Uncalibrated stone varies a lot more. Indian sandstone used to come at 25 to 40mm, and hand-cut setts and some limestone still vary.
- Hand-cut describes the edges: shaped by hand rather than sawn, for a rustic outline. Calibrated sandstone is often hand-cut too.
- Sawn stone has clean, crisp edges and a smoother character that suits modern designs. Even sawn stone isn't perfectly exact: one large supplier works to plus or minus 2mm on sawn stone and plus or minus 5mm on riven, against almost none for porcelain.
Slabs or setts?
Slabs, or flags, are the large pieces that make up most patios. Setts are small blocks, often 100mm square or 200mm by 100mm and 40 to 70mm thick, cropped by hand into a cobbled look. They suit drives, paths, courtyards and edging.
Check what a stone is made for before it goes under a car. Marshalls, for example, says its riven Indian sandstone slabs aren't intended for driveways, while its granite setts guide is written for them. Setts need a firm base too: Marshalls asks for at least 150mm of compacted sub-base under a sett drive.
Frost and slip
- Frost. The British Standard for natural stone paving slabs, BS EN 1341, includes a freeze-thaw test. Most of the UK gets frost, so ask for the stone's result. Porcelain absorbs 0.5% water or less, which makes it frost resistant.
- Slip. The UK's main measure is the pendulum test value (PTV). The Health and Safety Executive (HSE) rates 36 or more as low slip potential, 25 to 35 as moderate and 24 or less as high.
- R ratings. Porcelain is usually sold on its R rating, and makers such as Bradstone call R11 the sensible minimum outdoors. The HSE has reservations about the test behind R ratings and prefers the pendulum, so ask for a PTV as well if you can get one.
Does it need sealing?
No stone strictly needs it, but it makes cleaning easier. London Stone strongly recommends sealing sawn sandstone and limestone, and calls it worth doing on riven sandstone, granite or slate in a shady, damp garden where algae grows. Porcelain rarely needs it.
- An impregnating sealer soaks in and lets the stone breathe. A surface coating is cheaper but can trap moisture, go shiny or slippery and wear off.
- Seal only the top face, when the stone is completely dry. A sealed back won't bond to the mortar.
- Never seal over white bloom (efflorescence), or you lock it in. It fades on its own in time.
Laying basics
- Sub-base. Compacted crushed stone (MOT Type 1), laid and compacted in layers no deeper than 75mm. Marshalls' paving guide asks for at least 100mm for most garden paving, though its aggregates guide gives 75 to 100mm for patios. Go deeper on soft ground or anything that takes a car.
- Falls and levels. Build in a slight slope so rain runs off: Marshalls asks for at least 1 in 80 along the paving and 1 in 40 across it. Against the house, keep the finished surface at least 150mm below the damp proof course.
- A full mortar bed. Every slab sits on a full bed of mortar, typically 30 to 40mm before tamping down. Spot bedding, a few dabs under each slab, leaves gaps underneath: London Stone says a patio laid that way lasts no more than a couple of years before slabs rock and the pointing breaks up.
- Primer. A primer slurry brushed on the back of each slab helps it bond and stops marks drawing through. It's essential for granite, slate and porcelain.
- Mortar mix. Suppliers don't agree on this one. Marshalls asks for a wet, workable mix of 1 part cement to 3 or 4 of sharp sand; London Stone lays sandstone on a semi-dry 5 to 1 mix. Follow the guide for the stone you buy.
- Joints. Leave a joint, typically around 10mm for natural stone slabs, 5 to 8mm for porcelain and 8 to 15mm for setts. Don't butt slabs tight together: every slab has size tolerances, and the joint lets the paving move with the weather.
- Weather. Don't lay mortar in frost. Marshalls says to stop below 3°C on a falling thermometer.
- Cutting. Cutting stone makes silica dust, which damages the lungs. Use a saw with a water attachment or dust extraction and wear an FFP3 mask.
How much to order
Measure the area in square metres (length times width, split awkward shapes into rectangles), then add about 10% for cuts, breakages and slabs you set aside when sorting colours. Some suppliers suggest 10 to 15% for a design with lots of cuts. A patio 5 metres by 4 metres is 20 square metres, so order about 22.
Pack coverage usually includes a 10mm joint, so check the listing's figure is the laid coverage before you divide.
How it's delivered
- Paving comes in crates or packs on a pallet, by a lorry with a tail-lift. Delivery is usually to the kerbside, moved on a hand pallet truck that needs a hard, level surface: not gravel or grass.
- It's heavy. A pack of about 24 square metres of 18mm Indian sandstone weighs around 1.2 tonnes, or about 50kg a square metre, and 22mm stone is about a fifth heavier again.
- Someone needs to be there to check and sign for it. Note any damage on the delivery note before you sign.
- If it has to be unloaded on the road or pavement, you may need a permit from your council.
- Keep the stone covered and dry until you lay it.
Every slab is different
Natural stone varies in colour, texture and markings from slab to slab and crate to crate, and that's normal for natural stone. Some stones show iron spots or mineral marks after laying; they're cosmetic. Before laying, look through the slabs and mix them from more than one crate, keeping the odd ones for cuts or quiet corners. Porcelain is more even, but note its batch or shade code in case you need more later.
Where the stone comes from
Child labour and unsafe working conditions have been widely reported in India's sandstone quarries, so ask any supplier how it checks its supply chain, for example against the Ethical Trading Initiative (ETI) Base Code.
See also: how much gravel or bark? and getting it to your garden.
Please note: this guide is general advice to help you choose, not professional or legal advice. Every garden and every product is different, so always follow the maker's instructions and check with your council or a qualified tradesperson if you're unsure.
Sources for this guide
The pages we checked this guide's facts against, so you can read them for yourself. A link here isn't a recommendation.
- Marshalls: Natural stone paving installation guide (PDF); Indian sandstone paving; Indian sandstone 610 x 610 x 18mm datasheet (PDF); Garden paving technical information; How to lay cropped granite setts; What sub-base do I need?
- Bradstone: Is porcelain paving slippery when wet?
- Pavestone: Granite setts
- London Stone: How to lay Indian sandstone; Natural stone calibration; Sealing and pre-sealing paving; Our guide to choosing patio paving
- Stone Saver: Raj Green Indian sandstone: delivery, wastage and damages
- HSE: Assessing the slip resistance of flooring (PDF); Cutting paving, blocks, kerbs and flags
- Stone Specialist: Setting the standard: BS 1341 external paving
- Ethical Trading Initiative: Marshalls: tackling child labour in India