The LWF Blog

Fire Safety for Facilities Management Personnel – Structural Fire Protection – Part 154

June 13, 2022 11:16 am

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 153, LWF looked at structural fire protection and how it is utilised. In part 154, we continue on the subject by discussing doors and fire safety.

Doors and frames that deliver fire resistance are comprised of various types of materials and are suitable for differing environments. For example, timber doors are often used in commercial premises, unless particular high hazard areas or activities are involved. Other types of premises may require metal doors and shutters.

Modern timber fire-resisting doorsets incorporate an intumescent strip in either the door or the frame. The strip’s purpose is to swell if the temperature reaches a pre-determined level (usually 150 ºC) and once swollen, it will fill and seal the gap around the edge of the door, which is the point at which an ‘integrity failure’ may occur.

It is not likely that a timber door would achieve a fire-resistance of 30 minutes unless an intumescent strip was fitted. Often the fire resistance of a door is indicated by a colour-coded plug in the door edge and where applicable, the requirement for an intumescent strip. Although in the past, it was required that a fire-resisting door be 44 mm thick as a minimum with a 25 mm rebate, this may not be the case with modern fire-resisting doors.

An older fire-resisting door may not incorporate an intumescent strip and so is unlikely to afford 30 minute fire resistance if it was tested using modern methods. A fire risk assessment may not indicate that they need to be replaced, however, unless the fit of the door in the frame is poor. The decision will largely depend on context and the final decision on suitability will lie with the enforcing authority.

Any replacement fire-resisting door should comply with modern requirements.

Any door which is required to provide smoke control should be fitted with a smoke seal. A smoke seal is similar to a draught seal and will reduce the amount of smoke which can pass through the door before the temperature reaches the required level for the intumescent seal to operate.

While it is possible to access intumescent seals and smoke seals separately, it is also common to find combination intumescent/smoke seals and these are what is normally used on a timber door required to protect against the passage of smoke and fire. Any door which protects means of escape, within a protected stairway or a protected corridor must be equipped to protect against the passage of smoke and fire through the door and frame.

In part 155 of this series, LWF will continue to discuss fire and smoke resistant doors. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.


Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.

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