Ciria Report 108 Concrete | Pressure On Formwork

CIRIA 108 assumes internal vibration is stopped 1.5m below the current concrete level. If you over-vibrate (running the head too deep), you liquify the stiffened concrete, resetting the pressure to hydrostatic at that depth.

In the world of construction, few forces are as misunderstood—or as dangerous—as fresh concrete pressure on formwork. Every year, projects face blowouts, bulging forms, and even catastrophic failures because engineers and contractors underestimate the liquid-like pressure exerted by newly placed concrete. For decades, the industry struggled with inconsistent guidelines until a groundbreaking document changed everything: CIRIA Report 108, "Concrete Pressure on Formwork." ciria report 108 concrete pressure on formwork

Published by the Construction Industry Research and Information Association (CIRIA), Report 108 remains the gold standard for calculating lateral pressure exerted by fresh concrete on vertical and inclined formwork systems. Despite being originally released in the 1980s (with updates in subsequent years), its principles continue to inform modern design codes, including ACI 347 and EN 12812. CIRIA 108 assumes internal vibration is stopped 1

This article provides a comprehensive breakdown of CIRIA Report 108—its history, key formulas, practical applications, and why it remains indispensable for safety and efficiency in concrete placement. The genius of Report 108 lies in its

The genius of Report 108 lies in its classification of concrete based on "stiffening time." The report recognizes that concrete does not set instantly. It defines categories (Tables within the report) that correlate temperature and mix properties to how quickly the concrete transitions from a fluid to a solid state.

Crucially, the report places a "cap" on pressure. Even if the rate of rise is high, the pressure will not increase indefinitely. It levels off once the concrete at the bottom has stiffened enough to support the load of the concrete above it.