Formwork hydrostatic pressure
The pressure if concrete behaved as a liquid to the full pour height. Real design pressure is often lower.
Method
p = unit weight × height. Worked case: 25 kN/m³ over 3 m is 75 kN/m².
CIRIA C766 uses pour rate, temperature and concrete behaviour. This page does not. A temporary-works coordinator still has to design the form. See temporary works limit.
What the pressure bound is
This page is the hydrostatic upper bound: pressure equals density times gravity times the head of fresh concrete. It is the pressure you would get if the concrete acted as a liquid to that depth. It is not CIRIA C766 and not a formwork design.
The bound is useful because real concrete pressure is often lower once the concrete starts to stiffen, and sometimes the hydrostatic value is still the safe screen. The page does not know the rate of rise, the temperature or the concrete type. Those are why C766 exists.
Head is the vertical height of fresh concrete above the point you care about, not the height of the wall if the pour is staged. A 4 m wall poured in two lifts is not a 4 m head unless both lifts are fluid together.
Use it to see the upper order before a temporary-works design. The tie load, the ply thickness and the soldier spacing are not on this page.
- Related: concrete volume
- temporary works
Last checked 3 October 2026. A scenario, not a design. See methodology, standards and the disclaimer.