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Fire Door Guide
Fire Door Drop Seals: What They Are and How They Work
A fire door drop seal is an automatic threshold seal fitted to the bottom edge of a suitable door leaf. When the door closes, a mechanism lowers the seal towards the floor to help close the gap beneath the door where the assembly specification requires it.
Use this guide as a practical introduction, then check the relevant tested system and manufacturer documentation before selecting or installing a product.
Use This Guide
Understand the principle first
Use this guide as a practical introduction, then check the relevant tested system and manufacturer documentation before selecting or installing a product.
Fire Door Guide
Quick Guide
A fire door drop seal is an automatic threshold seal fitted to the bottom edge of a suitable door leaf. When the door closes, a mechanism lowers the seal towards the floor to help close the gap beneath the door where the assembly specification requires it.
Key Points
What You Need to Know
Automatic Action
Lowers when the door closes.
Threshold Gap
Addresses the gap beneath the door.
Door Compatibility
Must suit the particular door assembly.
Floor Finish
The threshold surface can affect sealing performance.
Key Principle
What Is a Door Drop Seal?
Drop seals are generally recessed or surface-mounted into the lower edge of a door. A plunger or similar mechanism is activated as the door closes, causing the seal to descend.
The product may provide smoke, acoustic or other performance depending on its design and supporting evidence.
Practical Guidance
Why the Threshold Gap Matters
Doors require operating clearances so that they can open and close. The gap at the threshold can influence smoke leakage, acoustic performance and other properties of the assembly.
The permitted gap and any required threshold sealing should be confirmed from the door specification.
Selection & Application
Drop Seals vs Perimeter Seals
Perimeter intumescent and smoke seals are typically fitted around the sides and head of the leaf or frame. A drop seal addresses the threshold and operates mechanically as the door closes.
They perform different roles and one should not be assumed to replace the other.
Important Detail
Selection and Installation
Check the fire door assembly, leaf thickness, floor finish, required clearance and performance evidence before selecting a drop seal.
Routing or altering a fire door leaf should only be carried out where the proposed detail is permitted by the door evidence and manufacturer guidance.
Relevant Products
Explore Related Product Ranges
Use the guide to understand the application, then browse the relevant Fire Protection Direct product categories.
Frequently Asked Questions
Frequently Asked Questions
It is an automatic threshold seal designed to lower when a suitable door closes and help seal the gap beneath the leaf.
No. Intumescent strips are generally fitted around the door perimeter and react to heat, while a drop seal mechanically closes the threshold gap.
No. The proposed product and any routing or alteration should be compatible with the specific door assembly evidence.
Performance can be affected by the threshold surface. Product adjustment ranges and installation requirements should be checked.
Some products have acoustic performance claims, but this should be confirmed from the relevant product data and door system requirements.
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