Slabs for a 12 × 8 ft shed base, by slab size
A 12 × 8 ft shed is a large workshop or a store for garden machinery and furniture. The base here is 3.6 × 2.4 m, converted at 0.3 m per foot, which leaves it marginally smaller than the shed floor as most shed makers ask (check your shed's instructions). The layout column shows where whole slabs fit with tight joints; the last column is the paving calculator's count with 10 mm joints and 10% for cuts and breakage.
| Slab size | Layout | Slabs by area | Slabs to buy |
|---|---|---|---|
| 600 × 600 mm | 6 × 4, no cuts | 24 | 26 |
| 450 × 450 mm | Needs cuts | 43 | 45 |
| 400 × 400 mm | 9 × 6, no cuts | 54 | 57 |
| 300 × 300 mm | 12 × 8, no cuts | 96 | 99 |
| 600 × 300 mm | 6 × 8, no cuts | 48 | 51 |
| 900 × 600 mm | 4 × 4, no cuts | 16 | 18 |
Twenty-four slabs, or time to price concrete
Six by four is 24 slabs, and 26 with the calculator's joints and spares. That is a lot of lifting and levelling, and it is about the size where a poured base starts to compete: the same 3.6 × 2.4 m in concrete is 0.95 m³, so an order of 1.00 m³ of ready-mix.
If you stay with slabs, 900 × 600 mm ones cover the same base in 4 by 4, which is 16 slabs and fewer joints, though each one is a two-person lift.
Sub-base and bed for 3.6 × 2.4 m
| Layer | Quantity |
|---|---|
| MOT Type 1 sub-base, 100 mm | 2.00 tonnes |
| MOT Type 1 sub-base, 150 mm (soft ground) | 2.99 tonnes |
| Sharp sand for a 30 mm sand bed | 0.44 tonnes |
| Or a 40 mm mortar bed at 6:1 | 0.65 tonnes of sharp sand and 4 bags of 25 kg cement |
Quantities include 5% extra. Check for buried services before you dig, using the free LSBUD service. Shed base options compared weighs slabs against concrete, a plastic grid and a timber frame, and the concrete version of this base is on how much concrete for a 12 × 8 ft shed base.
Want to change anything else? The calculator above is the full Paving Slab Calculator (UK): edit any number and the results update instantly.
Tools & materials for this project
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Frequently asked questions
How many slabs do I need for a 12x8 shed base?
24 slabs of 600 × 600 mm, laid 6 by 4, cover the 3.6 × 2.4 m base with tight joints and no cuts. Buy 26 to have 2 spares; that is the paving calculator's count with 10 mm joints and 10% extra.
What goes under the slabs for a 12x8 shed base?
About 100 mm of compacted MOT Type 1 (2.00 tonnes for this base) and a 30 mm bed of sharp sand (0.44 tonnes). On soft ground use 150 mm of sub-base, which is 2.99 tonnes.
Is it easier to concrete a 12x8 shed base than to slab it?
It is close. Slabs are 24 of 600 × 600 mm to lay and level one at a time; concrete is 0.95 m³, about 1.00 m³ of ready-mix, placed in one go but with shuttering to build first.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check the Building Regulations and your supplier's guidance before ordering.