When exposed to fire, most softwoods char at about 0.66mm/min and most hardwoods about 0.5mm/min. The fire performance of a timber structural element will obviously depend on these charring rates and the loadbearing capacity of the residual timber.
If the calculated residual timber is inadequate, Promat can offer various solutions normally using a board encasement. Promat also has systems for the protection of timber rafters or bearers where they pass through a fire rated wall. These can be protected either with spray or board systems. Contact Promat technical department for more details.