Fitting drop-down seals for better fire door safety

It’s Fire Door Safety Week, making it the right time to focus on something that often gets missed but plays a critical role in protecting lives and property during a fire: drop-down seals.

Whether you’re preparing a new build or updating existing internal and external doors, these seals are essential for stopping the spread of smoke, the biggest killer when a fire is active. They support fire compartmentation, protect escape routes, and help buildings meet UK safety regulations.

This guide covers what drop-down seals do, why they matter for fire safety, and how to fit them properly to ensure they function when it matters most.

What are drop-down seals and why they matter

A drop-down seal is a mechanical seal that automatically lowers when the door is closed, filling the gap at the bottom of the door. When the door is opened, it lifts back up.

That gap might seem insignificant, but in the event of a fire, this gap can allow smoke to spread rapidly between rooms. A fitted drop-down seal creates a reliable barrier that slows this spread, buying crucial time for evacuation and reducing damage.

In many settings, including schools, hospitals, care homes and offices, they are not just a recommendation. They are a requirement under building regulations and fire door specifications.

Installing certified drop-down seals helps fire doors perform to standard. Without them, even the best-rated fire door may fall short of what’s needed in an emergency.

How to fit a drop-down seal correctly

Whether you’re working on timber fire doors, acoustic doors, or metal door sets, the installation method will vary slightly depending on the product. But the principles are consistent. A correct fit ensures the seal works reliably for years to come.

1. Choose the right product for the application

Drop-down seals come in different types. Some are face-fixed to the surface of the door. Others are mortised into the bottom edge.

Face-fixed models are quicker to install and are often used in retrofit projects. Mortised options offer a cleaner finish and are usually selected for new builds.

Although they can be used on standard doors to protect against sound and draughts, for a fire door installation, always check your fire door certification for the permitted styles or application type required.

2. Prepare the door

For mortised drop-down seals, you’ll need to rout or chisel a recess into the bottom edge of the door. Please note this must be carried out by Certified installers – please check your door certification for guidance. This must be done with precision. An uneven cut or misalignment could stop the seal from deploying correctly.

With face-fixed versions, mark the mounting position on the door leaf. Keep it straight and level, close to the bottom edge.

Before fixing the seal in place, check that it fits within the door’s clearances, and the drop is suitable for your gap. Check for a self-levelling style for uneven floors.

3. Check seal orientation

Some drop-down seals are single-activation, meaning they are triggered by the door closing against the hinge side. Installing it the wrong way around is a common error and will stop the seal from working at all.

Double-check the instructions, and ensure the activation button is located correctly.

4. Secure and adjust

Once fitted, test the door to ensure the seal drops fully when the door is closed, making contact with the floor or threshold without resistance. If it drags or leaves gaps, use the adjustment screw (usually located on the end cap) to fine-tune the drop.

The seal should compress gently, not forcefully. A proper seal avoids damage to floor coverings and ensures consistent protection against fire and smoke ingress. A threshold place can ensure a secure seal when the drop seal falls.

5. Test the full assembly

With the seal in place, close the door and inspect all edges. Check that any intumescent strips and frame seals work together with the drop-down seal, without interference.

If the door is part of a fire-rated assembly, this final step helps confirm that every component is contributing to the fire-resisting performance of the complete doorset.

Small detail, major impact

Fire Door Safety Week exists to highlight the importance of every component that contributes to effective fire protection. Drop-down seals are one of those components. Often hidden and easily forgotten, their performance becomes critical in the event of a fire.

Without a functioning drop-down seal, even a certified fire door can fail to protect against smoke during a fire. With one fitted and maintained, the door becomes a much more effective barrier, protecting lives and supporting safe evacuation.