BS 8214:2026: A Practical Guide to Fire Door Threshold Sealing

Learn how BS 8214:2026 changes the approach to fire door threshold sealing and what installers and specifiers need to consider.

BS 8214:2026, published in March 2026, replaces BS 8214:2016 and introduces updated recommendations for the design, specification, installation and maintenance of fire-resisting and smoke control doors.

One important change for installers and specifiers is the greater emphasis on smoke leakage performance at the threshold. Where smoke sealing is required, the gap beneath the door should be considered as part of the overall performance of the complete doorset.

In this guide, we explain what BS 8214:2026 means for fire door threshold sealing, how the approach to threshold gaps has changed, and what to consider when selecting a suitable sealing system.

WHAT IS BS 8214:2026?

BS 8214:2026 is the British Standard code of practice for fire-resisting and smoke control doors. It provides guidance on their design, specification, installation and maintenance.

The updated standard has a wider scope than the 2016 edition, covering fire-resisting and smoke control doors made from a range of materials, including timber, steel and composite.

It also places greater emphasis on the performance of the complete door assembly, rather than considering individual components in isolation. This includes the door leaf, frame, sealing systems, ironmongery and surrounding construction.

For installers and specifiers, this reinforces the importance of ensuring that components are compatible with the fire door and supported by appropriate test evidence.

HOW HAS BS 8214:2026 CHANGED FIRE DOOR THRESHOLD SEALING?

For many years, a nominal 3mm gap beneath a fire and smoke control door has been used as a practical reference point. However, BS 8214:2026 takes a more holistic approach, focusing on the smoke leakage performance of the complete door assembly.

Where smoke sealing is required, BS 8214:2026 refers to a leakage rate of no more than 3 m³/h per metre at 25 Pa, when tested using the relevant smoke leakage test method.

This means the threshold should be considered alongside the head and jambs, with the emphasis now on demonstrated performance rather than meeting a specified gap width alone.

Rather than simply asking whether the gap beneath the door is 3 mm, we should now be asking:

Does the door assembly meet defined smoke leakage limits when tested to recognised standards?

For installers and specifiers, this means looking beyond the physical gap, checking the specification before installation, selecting products with appropriate evidence and following the manufacturer's installation requirements.

INSTALLING DROP DOWN SEALS FOR FIRE DOOR THRESHOLD SEALING

A suitable bottom-of-door sealing system may be needed to close the gap between the door leaf and the floor or threshold.

BS 8214:2026 recognises suitable systems, such as drop down seals, as an appropriate solution for achieving the required level of smoke control when correctly specified and installed.

Drop down seals can be rebated into or surface mounted onto the bottom of the door. When the door closes, the seal automatically drops to create contact with the floor or threshold, and retracts when the door opens.

For applications where the floor is uneven or changes between different materials, such as wood and carpet, a threshold plate is also recommended. The plate provides a consistent surface for the seal to contact, helping to create a more effective and continuous seal beneath the door.

WHAT SHOULD INSTALLERS AND SPECIFIERS CONSIDER?

When selecting a threshold sealing system, consider:

• Is the product suitable for the specific type and construction of the door?
• Does it have appropriate test evidence for the required application?
• Can the seal accommodate the threshold gap?
• Is the floor level and suitable for the seal to make consistent contact?
• Can the product be installed in accordance with the door manufacturer's specification?
• Will the sealing system work as part of the door assembly without compromising its performance?

The correct solution should be selected based on the performance requirements of the door, its construction and the surrounding threshold conditions, not simply because it fits the available gap. 

HOW FIRESEALSDIRECT CAN HELP WITH THRESHOLD SEALING

At FireSealsDirect, we stock a range of fire door solutions, including drop down seals and threshold plates, from leading manufacturers including Lorient, CCE and Norseal.

If you need help selecting a suitable product for your application, our team can provide guidance on product suitability and installation requirements.

For advice, contact us at [email protected] or call 02920 859 959.

Alternatively, you can visit our Advice Centre, which contains helpful guides and information.