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Average building fire temperatures range from approximately 700º to 900º Celsius. Steel weakens dramatically as its temperature climbs above 230ºC, retaining only 10% of its strength at about 750ºC.

As a rule, wood will not ignite until it reaches a temperature of around 250ºC. Once it catches fire, wood typically develops char at the rate of 0.64mm per minute under severe fire conditions. The char naturally insulates the wood and raises the temperature level it can withstand. Thus, in a 30-minute fire, only 19mm of each exposed surface of the glulam is lost to charring, leaving most of the original cross section intact.

FIRE SAFETY
In nearly every country, one or more regulatory agencies concern themselves with the fire safety of building materials and systems. In the U.S., these include:

• Model Building Code organizations - develop design requirements, compliance criteria and regulatory oversight for building construction. Regulatory agencies participate in the development of these provisions.
• American Society of Testing Materials (ASTM) - promulgates fire test methods for building materials and systems.

• ASTM Test Method E-119 approximates actual fire conditions for building assemblies (beams, walls and connectors) and results in the development of fire-resistance ratings for building assemblies.

• ASTM E-84 Standard Test Method for Surface Burning Characteristics of Building Materials provides data on flame-spread ratings / classifications and smoke-developed indexes for materials.

Steel beams have melted and collapsed over charred timber beam, which, despite heavy damage, remains in place.

406mm, 60 kg/m steel beam (#W16x40) and 178mm x 533mm glulam beam following fire testing under full load. Steel beam collapsed after only 30 minutes of exposure while the glulam member remained straight and true, charring on 19mm on exposed surfaces.