Intumescent Strips

Intumescent strips are an essential part of any fire-rated door system. These heat-sensitive seals are designed to expand rapidly in the event of a fire, sealing the gap between the door and the frame to slow the spread of flames, smoke, and toxic gases. By maintaining compartmentation, intumescent fire door seals play a crucial role in preserving escape routes and protecting lives and property.

Our full range of intumescent fire door strips has been independently tested and certified to meet UK fire safety standards, giving you the confidence to install them in both commercial and residential settings. Choose from Fire Only strips or combined Fire and Smoke intumescent seals, depending on your door specification and compliance requirements.

Important fitting advice: When installing fire door hinges, don’t overlook the need for intumescent hinge pads. These must be used to maintain the fire rating and ensure the fire door assembly performs as tested.

Looking for more guidance? Read our Ultimate Guide to Fire Door Hardware for up-to-date compliance information, British Standards references, and installation best practices.

Intumescent Strips FAQ's
Can intumescent strips be painted over?

Generally no, however there are some specialist strips that are designed to be painted over without compromising their effectiveness. However, it’s important to use the appropriate type of paint, as certain paints or coatings may affect the strip’s expansion properties during a fire. Always follow the manufacturer’s guidelines regarding painting.

How do I know if I need to replace my intumescent strip?

If the strip is cracked, damaged, or deteriorating, it should be replaced. Additionally, if a fire has occurred or the seal has been disturbed, it’s crucial to inspect the strip for integrity. 

How do I fit intumescent strip around hinges and locks?

Strip is generally stopped at the hinge, and restarts after. However the hinge itself must be fitted with intumescent sheet / pads under the hinge. 

The same applies to lock keeps, where an intumescent kit should be fitted under the keep. 

Why fit intumescent strips?

Enhanced fire safety: They help to contain fires, preventing them from spreading rapidly. 

Smoke and gas protection: Intumescent strips can prevent smoke and harmful gases from leaking through gaps. 

Cost-effective: They are an affordable fire safety measure compared to installing full fire-resistant doors or windows. 

Easy installation: They can be retrofitted into existing doors and frames. 

Do intumescent strips require any special maintenance?

Intumescent strips typically don’t require regular maintenance. However, they should be inspected periodically to ensure that they are intact and undamaged. If the strip is compromised (e.g., cracked, torn, or degraded), it should be replaced promptly to ensure continued fire protection.

How do Intumescent strips work?

The intumescent material in the strip reacts to the heat of fire and expands to seal gaps between the door and frame, preventing the passage of flames, hot gases, and smoke.

What types of intumescent strip are available?

Two types are available, with or without smoke seal. 

Smoke seal strips generally have a brush seal fitted that stop the spread of smoke before the heat of a fire builds sufficiently for the intumescent seal to expand.  

What are intumescent strips?

Intumescent strips are fire-resistant plastic strips with a centre of intumescent material that expands when exposed to heat to seal fire doors to their frames and prevent the spread of fire. 

Do I have to route a groove to fit intumescent strips?

Yes, nearly always intumescent strips fit into a pre routed groove and are generally self-adhesive. 

However we do stock a surface mounted version that can be fitted where there is a larger gap between the door and frame. 

Should the strip be fitted to the door or the frame?

Intumescent strips should be fitted to the door frame, not the door itself. Fire tests are undertaken with the strip fitted to the frame.  

However, in the case of double doors with plain meeting style one side of the meeting doors should be fitted with a brush seal that butts against a plain strip fitted to the opposite door.  

Where are intumescent strips fitted?

Commercial buildings, public buildings, residential homes, and places that require fire-resistance ratings as part of building code compliance.

What lengths is intumescent strip supplied

There are 2 common lengths, 2100mm and 1050mm. 2100mm allows for a continuous length to the sides of the door. Strips are easily cut with a builder's knife or small hacksaw.

What sizes does intumescent strip come in?

The 3 popular sizes of intumescent strip are: 10x4mm for 30 minute fire doors, 15x4mm for both 30 minute and 60 minute fire doors, and 20x4mm for 60 minute fire doors. 

How long do intumescent strips last?

Intumescent strips are designed to last for several years when properly installed. However, their effectiveness can be compromised by environmental factors such as excessive moisture, UV exposure, or physical damage. It’s recommended to inspect and replace intumescent strips as part of regular fire safety maintenance, especially after a fire or significant wear and tear.