For most latched single-leaf single-swing 30 minute (FD30) timber fire-resisting door assemblies, a single 10 mm x 4 mm strip of
Therm-A-Seal down each jamb and across the head will normally suffice.
Unlatched single-leaf assemblies may be satisfactory with a 10 mm x 4 mm Therm-A-Seal but, depending on the nature of the door, it may be necessary to increase the size to 15 mm x 4 mm.
Some latched single-leaf single-swing 60 minute (FD60) timber fire-resisting door assemblies, will satisfy the requirement of the BS476: parts 20 and 22: 1987 test procedures when fitted with a single 20 mm x 4 mm strip across the head and down both jambs.
If improved performance is required, a pair of 15 mm x 4 mm will ensure better protection around the hinges and across the head.
The intumescent foam produced by Therm-A-Seal has high temperature tolerances and so is well suited for use with steel
framed timber door assemblies where conventional intumescent foams may break down.