Fire spread in a large compartment with exposed cross-laminated timber and open ventilation conditions: #FRIC-01 – Exposed ceiling

Exposing cross-laminated timber (CLT) structures in buildings is increasingly popular in modern buildings. However, large timber surfaces, window facades, and different geometries can change the fire dynamics in a compartment. The effect of those parameters, therefore, needs to be studied. Two large-scale CLT compartment fire experiments (95 m2) have consequently been performed. The experiments were designed to represent a modern office building with an open-plan space and large window openings. In this experiment, #FRIC-01, the ceiling was exposed. The wood crib fire developed slowly and travelled approximately 1.5 m before the ceiling ignited at 32.5 min. Thereafter the fire spread rapidly across the ceiling and wood crib before it shortly after retracted. Three such cycles of rapid spread followed by a retraction occurred within 13 min, whereby the wood crib fire grew larger for each cycle. After the flames extended through the compartment for the fourth time, the fire remained fully developed. After a short period of intense burning, the CLT self-extinguished while the wood crib fire was still burning. The compartment withstood full burnout, and no reignition occurred despite some delamination and using an adhesive that lacks a demonstrated resistance against glue-line integrity failure.