How to plan and pour a small concrete slab
A patio, shed base or path is a good first concrete job. Most problems come from poor ground preparation, too little concrete or drying too fast. Follow these steps.
Open the tool: Concrete Calculator
1. Measure and order
Mark out the slab and measure length, width and thickness. Enter them in the calculator and add 10% extra. Buy bags for small jobs and order ready-mix above about one cubic yard.
2. Prepare the ground
Dig out the soil to the slab thickness plus about 4 inches (10 cm) for a compacted gravel base. Remove roots and soft spots, then compact the base well.
3. Build the forms
Set timber boards around the edge with stakes every 3 ft (1 m). Check the top is level, or falls about 1 in 100 away from buildings so water runs off. Add mesh or rebar on chairs if the slab needs it.
4. Pour and level
Fill the forms in one go, starting at the far corner. Pull a straight board across the top in a sawing motion to level it, then smooth it with a float.
5. Finish and cut joints
When the shine of water has gone, finish with a float or broom for grip. Cut control joints about every 8 to 10 ft (2.5 to 3 m), a quarter of the slab depth.
Checklist
Before and after the pour:
- Check the weather: avoid frost and very hot, windy days.
- Have enough helpers, tools and a wheelbarrow ready.
- Wear gloves, boots and eye protection: wet cement burns skin.
- Keep the slab damp or covered for at least 7 days.
- Walk on it after about 2 days and drive on it after about 7 to 10 days.
- Check local rules: some slabs need a permit or inspection.