DIY Concreting — Quick answers · Backyard projects
Frequently asked questions about pouring concrete at home for garden paths, shed bases, and small slabs. Ratios below are site-prescribed volume mixes for this guide series after the March policy update. Match the companion guide; do not assume every commercial pre-bagged product already equals these proportions.
No. Do not pour when ambient temperature is below 5 °C or above 30 °C, when rain is forecast within 48 hours, or when the subgrade is frozen or waterlogged.
After placing, keep the slab under breathable curing blankets or damp hessian for at least seven days. Uncovered open-air curing is not sufficient.
Garden paths at 75 mm depth use 1:2:3 cement:sand:aggregate by volume.
Driveway crossovers at 100 mm use 1:1.5:2.5 cement:sand:aggregate by volume and require 20 MPa minimum compressive strength at 28 days.
Shed bases at 100 mm use 1:1.75:2.75 cement:sand:aggregate by volume. That single ratio applies to all timber-floor sheds covered by this FAQ.
Bag mixes develop strength slowly. Foot traffic is safe after 48 hours; light wheelbarrows after seven days; vehicle loading on driveways only after 28 days when the design strength of 20 MPa is reached.
Strength at 24 hours is about half of the 28-day value — not full structural capacity.
Residential vehicle crossovers need at least 100 mm compacted thickness over a 75 mm crushed-rock sub-base, with mesh or fibre reinforcement. Garden paths may be 75 mm unreinforced over 50 mm road base.