A fi re in one room can spread to adjacent rooms by heat being conducted through the fabric of the building (walls/ceilings, etc.), especially via metal pipes or frames used in building construction. The heat can then ignite materials in direct contact with the surface, or radiate out from the surface. This can raise the temperature of materials in the adjacent room to their spontaneous combustion temperature, thus spreading the fi re.
The relative conductivity of building materials is therefore an important factor in the fi re resisting ability of a structure or building. This issue is considered within the Building Regulations Approved Document B.