Can You Use Sharp Sand as a Sub-Base?

Using Sharp Sand as a Sub-Base

Easy to work with and level — smooth to rake and screed.
Widely available and affordable from most builders’ merchants.
Provides a nice bedding layer over a proper base.

Using Sharp Sand as a Sub-Base

Doesn’t compact properly — stays loose even with a wacker plate.
Shifts and settles under load, especially with foot traffic or weather.
Traps moisture — can lead to frost damage or slab movement over time.
Not strong enough to support slabs, blocks, or concrete long-term.

Using a Proper Sub-Base (e.g. MOT Type 1)

Compacts into a rock-solid foundation — ideal for paving or concrete.
Supports heavy loads and prevents movement or sinking.
Drains well and maintains structure through all seasons.
Recommended by building regs and trade professionals.

Using a Proper Sub-Base (e.g. MOT Type 1)

Heavier to work with and takes longer to install in layers.
More expensive than just using sand — though worth it long-term.
Needs a plate compactor for proper installation.

✔ Bedding layer for slabs and blocks

Sharp sand is ideal for laying slabs or blocks — it gives you a smooth, adjustable surface to set each one into place.
✔ Not a load-bearing sub-base

On its own, sharp sand shifts under weight and holds water. It doesn't form a solid, compacted layer like MOT Type 1 does.
✔ Used over a compacted sub-base

You can rake sharp sand over compacted hardcore or Type 1 to level things out before laying slabs — but it’s never a replacement.
✔ Not suitable for driveways or footings

If it’s going under something heavy or structural — like concrete, bricks, or block paving — sharp sand won’t hold up.
✔ Works well with mortar laying too

Sharp sand is also a key ingredient in mortar mixes — ideal for laying slabs on full beds when mixed with cement.

Material	Suitable for Sub-Base?	Notes
MOT Type 1	✅ Yes	Best choice — compacts well, drains, and supports heavy loads
Sharp sand	❌ No	Great as a bedding layer, but not stable or strong enough underneath
Recycled hardcore	✅ Yes (if clean and compacted)	Suitable as long as it’s crushed, clean, and well compacted
Ballast	⚠️ Sometimes	Can work for small projects, but doesn’t compact as tight as Type 1
Soft sand (builders sand)	❌ No	Too fine and slippery — moves around and holds moisture

🔹 Can I use sharp sand under paving slabs?

You can use sharp sand as a bedding layer under slabs — but only on top of a solid, compacted sub-base like MOT Type 1. Sharp sand helps level and position each slab but won’t support them long-term on its own. If you skip the sub-base, you risk dips, movement, and cracks down the line.

🔹 Can sharp sand be compacted with a wacker plate?

You can try compacting sharp sand with a plate compactor, but it won’t lock together like crushed stone. It may feel firmer, but under load it can still shift or settle. That’s why it’s best used over a properly compacted sub-base, not as one by itself.

🔹 Is sharp sand strong enough to support concrete?

No — concrete should never be poured directly onto sharp sand alone. The sand can wash out, compress, or shift, which leads to cracking and uneven slabs. Always use a compacted stone base like MOT Type 1 under any concrete pour for long-term strength and stability.

🔹 What’s the difference between sharp sand and soft sand?

Sharp sand has coarse, angular grains that make it ideal for bedding and mortar. Soft sand (also called builders sand) is much finer and smoother — great for bricklaying mortar, but not for laying slabs or bedding. Sharp sand holds its shape better under slabs and drains more freely.

Can You Use Sharp Sand as a Sub-Base?

Using Sharp Sand as a Sub-Base

Using Sharp Sand as a Sub-Base

Using a Proper Sub-Base (e.g. MOT Type 1)

Using a Proper Sub-Base (e.g. MOT Type 1)

What Sharp Sand Is (and Isn’t) Good For

Sub-Base Material Comparison

Free Quote for Concrete Flooring in the UK