The plan
This is a patio for sitting on, not a driveway: 100 mm of compacted MOT Type 1 under it, then a 40 mm sharp sand bedding course, then the slabs. The paving calculator in the plan below is the same engine the paving calculator page runs, so the take-off is what that page would give you for these numbers.
The layout is a simple running grid, 600 × 600 mm slabs with 10 mm joints. Nothing is cut except the edges, which is why the cutting allowance is 10% rather than more.
Doing it, in order
- Set out the patio with pegs and a line, checking both diagonals are equal so the corners are square.
- Excavate to the depth of the build-up: 100 mm sub-base, 40 mm bedding, plus the slab thickness, and allow for the fall away from the house.
- Lay and compact the MOT Type 1 sub-base in two layers, watering it as you go if it is dusty.
- Bed the edge restraint on a concrete haunch along the open sides — the sides that meet soil or a drop.
- Screed the sharp sand bedding to a consistent 40 mm, then lay the slabs on the module, tapping each one down to the line.
- Point the joints with jointing sand or a paving grout, then keep people off it for the time the manufacturer asks for.
Don’t forget
- Jointing sand or paving grout The calculator returns this as "estimate only": coverage depends on the joint width and the product, so check the maker's chart rather than trusting a figure here.
- A fall away from the house A patio has to fall away from the building so water does not sit against it. How much depends on the surface and the manufacturer's own guidance, so there is no figure for it on this page.
- Where the spoil goes Excavating for the build-up produces a skip-load of soil and subsoil. Decide before you start where it is going.
- Edge restraint on the open sides The calculator sizes it from the perimeter of the patio, which is 14 m here. Only the edges that meet soil or a step need it.
Material take-off for this plan
Worked out by the site’s own Paving for this plan’s dimensions, not typed in by hand.
The working
| Working | Value |
|---|---|
| Paving area | 12.0 m² 4.00 m × 3.00 m |
| Slabs per row | 7 across × 5 down 600 × 600 mm with 10 mm joints |
| Slabs before waste | 35 Plus 10% for cuts and breakages |
| MOT Type 1 sub-base | 2.16 t 12.0 m² × 100 mm × 1.8 t/m³ |
| Sharp sand bedding | 0.77 t 12.0 m² × 40 mm × 1.6 t/m³ |
What to order
| Material | Quantity | Notes |
|---|---|---|
| Paving slabs 600 × 600 mm | 39 slabs | 7 × 5 = 35 plus 10% for cuts. |
| MOT Type 1 sub-base | 2.16 tonnes | ≈ 3 × 850 kg bulk bags at 100 mm compacted. |
| Sharp sand (bedding) | 0.77 tonnes | ≈ 31 × 25 kg bags, or 1 bulk bags, at 40 mm. |
| Edge restraint / kerb and concrete haunch | 14 m | Rule of thumb: the open perimeter, 14.0 m here. An edge that is not restrained lets the paving spread — a kerb on a concrete haunch, or a proprietary edge, is what holds it. Only the edges that meet soil or a drop need it. |
| Jointing sand or paving grout | estimate onlyestimate | Check the manufacturer's coverage for your joint width. |
Sub-base depth is the one number people get wrong. 100 mm compacted is fine for a footpath or light patio; go to 150 mm for anything a car will park on.
A small patio, planned out FAQs
How many slabs do I need for a 4 m by 3 m patio?
39 slabs of 600 × 600 mm with 10 mm joints, from the paving calculator. The grid takes 35 slabs — 7 across by 5 down — and the order is 39 once a 10% cutting allowance is added.
How much sub-base does a 4 m by 3 m patio need?
2.16 tonnes of MOT Type 1 at 100 mm compacted, which is about three 850 kg bulk bags. The calculator works it out as 12.0 m² × 100 mm × 1.8 tonnes per cubic metre.
How much sharp sand goes under the slabs?
0.77 tonnes at a 40 mm bedding depth, which is about 31 bags of 25 kg or one bulk bag. Bedding depth between 30 mm and 50 mm is the usual range.
Is 100 mm of sub-base enough for a patio?
For a footpath or a light patio, yes. Go to 150 mm for anything a car will park on. The paving calculator takes the depth as an input so you can see what the heavier figure costs.