Do Granite Setts Need Mortar or Sand Bedding?

One of the questions that comes up most often when people are planning a granite sett project is whether they need to use mortar or whether sharp sand will do. It's a fair question, and the answer isn't a simple yes or no — it depends on where the setts are going and what they need to do.

The Short Answer

For any area with vehicle access, you need mortar. For pedestrian-only paths and certain decorative garden applications, sharp sand can work perfectly well. Let's break down why.

Understanding the Two Methods

Sand Bedding (Dry)

Laying granite setts on a bed of compacted sharp sand or grit sand is the traditional approach for pedestrian areas, particularly where permeable drainage is desired. The setts sit on the sand bed, are compacted down, and the joints are filled with kiln-dried sand or grit.

The main advantage is flexibility — the surface can be lifted and relaid relatively easily, which makes sand-bedded installations popular for pathways and garden borders where underground services might need to be accessed.

The downside is that sand can wash out over time, particularly on slopes or in areas with high rainfall. Without periodic top-up of jointing sand, weeds will establish and levels will start to drop.

Mortar Bedding

A mortar bed (typically a semi-dry 4:1 mix of sharp sand and cement) provides a much more stable platform. Once the mortar has cured, the setts are essentially locked in place and significantly more resistant to movement, spreading, and frost heave.

For driveways taking vehicle traffic, this is non-negotiable. A sand bed simply won't withstand the lateral forces and repeated loading of cars driving over it.

Which Method for Which Application?

Application	Recommended Bedding
Domestic car driveway	Semi-dry mortar bed
Heavy vehicle access	Full wet mortar bed (consider concrete sub-base)
Pedestrian garden path	Sharp sand or semi-dry mortar
Decorative edging	Sharp sand (with fixed edge restraints)
Patio surrounded by lawn	Semi-dry mortar bed
Public or commercial area	Full wet mortar, specialist specification

What About Semi-Dry Mortar?

Semi-dry mortar (four parts sharp sand to one part Portland cement, mixed without water) is the most commonly used bedding method in domestic landscaping. It's spread like sand, which makes screeding and levelling easy, but the presence of cement means it hardens once it absorbs moisture from the setts and the atmosphere.

It gives you the workability of sand with most of the strength of wet mortar — which is why it's become the standard approach for driveway projects. Spread to approximately 30–40mm depth, screed level, then lay the setts directly onto the mix.

Jointing: Mortar or Sand?

The bedding method and the jointing method are separate decisions. Even on a mortar-bedded driveway, you might choose polymeric jointing sand (which hardens when activated with water) rather than a wet mortar joint. Polymeric sand is increasingly popular because it's flexible, weed-resistant, and doesn't crack like rigid mortar joints can.

For areas with very heavy loads, or for formal driveways where a clean, precise appearance is wanted, wet mortar pointing is still used. Choose a mortar mix that matches or slightly complements the colour of your setts.

Common Mistakes

Using building sand instead of sharp sand: Building sand is too fine and doesn't compact properly. Always use sharp sand or coarse grit sand for bedding.

Too much water in the mortar: A semi-dry mix should barely hold its shape when squeezed in your hand. If it's wet or sloppy, it'll shrink as it dries and your levels will drop.

Not compacting the bedding layer properly: The bedding needs to be flat and firm before the setts go on. Any soft spots will cause dips in the finished surface.

Laying in cold weather: Don't lay mortar-bedded setts when temperatures are below 5°C or when frost is forecast. The cement won't cure properly and you'll end up with weak, crumbling bedding.

What About Reclaimed Setts?

Reclaimed granite setts are more variable in size and thickness than new setts, which makes sand bedding actually more practical for them in some ways — you can adjust the depth at each stone. However, for vehicle areas, a mortar bed is still strongly recommended, and you'll simply need to adjust your bed thickness stone by stone. It takes longer but is perfectly achievable.

For more on the right materials and techniques, our full installation guide covers everything from base preparation to final finishing. And if you're looking at setts for a driveway project, browse our granite paving and setts and driveway paving collections for available sizes and finishes.

Getting the bedding right might not be the most glamorous part of the project, but it's what keeps your setts looking great — and staying level — for years to come.