Casting a strip foundation

Clarify frost-free depth, bearing capacity of the subsoil, the concrete's strength and exposure class, and reinforcement and cover from the project. These are specified by the designer in accordance with DS/EN 206 and DS 2426 — never make up classes, densities or reinforcement quantities yourself.

Excavate to frost-free depth and to firm, load-bearing ground as per the project. A soft or uneven bottom must be remedied before you pour — the foundation is only as good as what it stands on.

Erect the formwork plumb and to the correct line, and check with diagonal measurements that the corners are square. Brace the formwork so that it does not bulge under the pressure of the pour.

Lay the reinforcement (e.g. reinforcement mesh or bars, EN 10080) according to the structural drawing and maintain the specified cover with spacers. The cover protects the steel against corrosion — too little cover causes rust damage over time.

Calculate the volume as V = L · W · H (all in metres). A foundation of 10 m × 0.40 m × 0.60 m gives V = 2.40 m³. If the cross-section changes (thickening, plinth, step), split the pour into several boxes that are calculated separately and added together.

Add a waste allowance for an uneven base and overfill — e.g. 5 %: 2.40 × 1.05 = 2.52 m³. Order ready-mixed concrete by strength and exposure class as well as slump (DS/EN 206 + DS 2426); volume is ordered in m³.

Distribute the concrete and compact it (e.g. with a poker vibrator) so air pockets are driven out and the concrete surrounds the reinforcement. Protect against drying out too quickly and against frost during curing in accordance with current guidance.

Level the top of the foundation and lay the damp-proof course/moisture barrier before the bricklaying starts — see the guide «Damp-proof course and moisture barrier». The wall must start from a level top with the moisture barrier in place.