Preparing the slab

How to prep the slab

A six-step sequence a builder or competent DIYer can follow — or hand to your concreter.

1. 1Mark out the pad.

   At least 900 × 900 mm; 1200 × 1200 mm gives room to work and for future modules. Check the spot against the battery's clearance rules.

2. 2Excavate and compact the base.

   Lay and compact 100–150 mm of crushed rock so the ground underneath can't settle.

3. 3Add the bedding layer.

   Screed 25–30 mm of coarse sand flat, then lay a damp-proof membrane over it.

4. 4Pour the concrete.

   Commonly 75–100 mm, and thicker (100–150 mm+) for heavier or multi-module systems — usually over steel mesh. Your installer or concreter confirms the depth and reinforcement for your battery's weight.

5. 5Get it level.

   The finished surface must sit true. A battery on an out-of-level pad can void its warranty.

6. 6Drain it, then let it cure.

   Grade the surrounds so water sheds away and can't pool or soften the ground beneath the base. Let the slab cure (commonly about a week) before the battery is mounted.

The layers, as a general guide

Bottom to top. Ranges are typical — the exact figures come from your installer and the battery's own installation manual.

Pad footprintA single wall-format battery; larger for multi-module systems, plus clearances.

900 × 900 mm min1200 × 1200 mm gives comfortable working room

BaseCompacted crushed rock, well consolidated.

100–150 mm

BeddingCoarse sand, screeded flat; a damp-proof membrane usually goes on top.

25–30 mm

Concrete slabUsually steel-mesh reinforced. Thicker for heavier batteries — see the weight band.

75–100 mm+heavier / multi-module: 100–150 mm+

FinishThe single most important part.

level & well-drained