Intumescent Strips

• Fire-only strips are designed to expand under heat and seal the gap between the door and frame, protecting against flame spread.
• Fire and smoke seals do the same job but also feature an integrated brush or flipper (fin) that blocks "cold smoke" at ambient temperatures — before the intumescent has had a chance to activate. These are typically required for doors designated FD30s or FD60s (the "s" denotes smoke).

For the best protection on fire-only doors where smoke control is also needed, you can either choose a combined fire and smoke strip or pair a fire-only strip with a separate smoke seal.

Our most popular ranges

Our collection of Lorient intumescent strips is one of our best-selling ranges, offering fire-only, fire and smoke, and acoustic options. The Pyroplex range is also a firm customer favourite and carries full third-party certification.

Frequently Asked Questions

What width intumescent strip do I need?

The width required depends on the door's fire rating, the door leaf thickness, and the size of the gap between the door and frame. As a general guide, FD30 doors typically use a 15mm or 20mm strip, while FD60 doors usually require a 20mm or larger strip — sometimes two strips per edge. Always refer to the door manufacturer's certification, as fitting the wrong size can invalidate the door's fire rating. If you're unsure, our Technical Helpline can advise.

Do I need a fire-only or a fire and smoke seal?

If your door is designated FD30s or FD60s (the "s" indicates smoke control), you must use a fire and smoke seal. Standard FD30 and FD60 doors without the "s" only require a fire-only strip, though adding smoke protection is considered best practice in settings such as residential corridors, hotels and care homes.

How do I install intumescent fire seals?

Intumescent strips are fitted into a pre-routed groove in either the door edge or the frame (check the manufacturer's instructions for which is correct for your product). The strip is pushed firmly into the groove with the self-adhesive backing holding it in place — no mechanical fixings are usually required. The strip must run the full height of the door on both long edges, and across the top. It's important that the strip sits flush and is not painted over, as paint can restrict expansion.

For more information, visit our Advice Centre for the latest updates on regulations and specifications, or call our Technical Helpline for free, impartial advice.