Ciria Report 108 Concrete Pressure On Formwork May 2026

CIRIA 108 is intended for stationary forms. For slipforming, dynamic pressures are higher—consult separate guidance.

A. Clarity of Presentation The report utilizes clear charts and tables to derive coefficients ($C_1$, $C_2$) based on concrete temperature and cement type. For a site engineer or temporary works coordinator, the workflow is logical and easy to follow. The pressure diagrams (showing hydrostatic head vs. the design envelope) visually explain why the pressure is calculated the way it is.

B. The "Formwork Pressure" vs. "Hydrostatic" Distinction One of the most valuable sections explains the phenomenon of particle interference. As concrete stiffens, the aggregate particles begin to arch, transferring load to the sides of the formwork via friction, thereby reducing the pressure on the lower layers. R108 quantifies this reduction, leading to more economical formwork designs compared to assuming full liquid head. ciria report 108 concrete pressure on formwork

C. Practical Guidance on Restraint The report provides excellent guidance on the "kick" or the outward force generated during the placement of the first lift of concrete, and the importance of adequate restraint systems (props and ties). It addresses safety factors and load combinations with a site-focused perspective.

Scenario: Pouring an 8-meter-high wall.

Calculation: P_max = 1.2 × 24 × 2 × 2 = 115.2 kN/m²

Hydrostatic check: D × H = 24 × 8 = 192 kN/m². Since 115.2 < 192, the CIRIA value controls. You can design formwork for 115 kN/m², not 192. That is a 40% reduction in required tie strength. CIRIA 108 is intended for stationary forms

Advantages of Using CIRIA 108:

Limitations & Cautions: