How to fit a drop-down door seal for fire doors

In the event of a fire, smoke can quickly spread from room to room, reducing the visibility and breathable air of the building. This makes fire safety equipment that is specifically designed to minimise air flow, such as drop-down door seals, compulsory for a fire door to be fit for purpose. Here, we discuss the purpose of a drop-down seal, how it works, and how you can install it safely and effectively.

The purpose of a drop-down door seal

When a door is closed, air can still pass underneath. This is somewhat unavoidable as the door would drag and scrape across the floor without any space, making it difficult and impractical to use. Unfortunately, this also means smoke can easily travel under doors during a fire and flood multiple rooms.

A drop-down seal is fitted along the bottom of a fire door and works in unison with a latch on the frame. Once the door closes, a mechanism is activated whereby a seal drops down and covers the gap underneath the door and reduces the risk of smoke passing through.

Installing a drop-down door seal for fire doors can not only save lives, it can reduce air leakage and reduce energy costs.

How to fit a surface mounted fire door seal

Here is a step-by-step guide for how to install a surface mounted drop-down door seal.

You will need:

• Surface mounted drop-down door seal
• Screws
• Tape measure
• Pen/marker
• Screw driver
• Drill
• Saw
• Engineer’s file

1. You may need to adjust the length of your drop seal to match your door. Measure the bottom of your door (not including the frame) with a tape measure and lock the tape in place.

2. Look inside either end of your drop seal and identify which end has the catch (often a solid black square/circle shape). It is important to check this as you do not want to make the mistake of cutting off the wrong end.

3. Lay your tape measure along your door seal, starting from the above-mentioned end, and use your pen to mark 5mm less than the measurement of your door - this may vary depending on the drop down seal model, please follow the manufacturers fitting instructions.

4. Use the saw to carefully and safely cut the drop-down door seal to size, being sure not to remove more than what the manufacturer specifies.

5. File down the side of the seal you cut, making it as smooth as possible. This will be the end of the seal that is fitted on the hinge side of the door.

6. If you look inside the seal, you will see a narrow, triangular gap at the top. Insert the head of your screwdriver into this gap and push upwards to remove the outer shell. Keep this nearby as you will need it soon.

7. On the opposite end, slide out the inner workings of the seal and rotate the catch 180 degrees before reinserting.

8. Place the seal across the bottom of your door and push your pen through the screw holes to mark the correct points of drilling on your door. Remember, the 5mm you cut off must go at the hinge side of the door, and leave enough room for the door to open.

9. Drill holes into your door at the appropriate points.

10. Use the screw driver to insert the screws into the seal and fix it into the correct position.

11. Fit the plunger on the bottom of the door frame next to the seal.

12. Place the outer shell back over the seal and close the door to test the newly fitted surface mounted drop-down seal.

How to fit a rebated fire door seal

Here is a step-by-step guide for how to install a rebated drop-down door seal.

You will need:

• Rebated drop down seal
• Router bit
• Screws
• Tape measure
• Pen/marker
• Screw driver
• Drill
• Saw
• Engineer’s file

1. Remove the door from its hinges and lay on its side.

2. You may need to adjust the length of your drop seal to match your door. Measure the bottom of your door with a tape measure and lock the tape in place.

3. Look inside either end of your drop seal and identify which end has the catch (often a solid black square/circle shape). It is important to check this as you do not want to make the mistake of cutting off the wrong end.

4. Use the saw to carefully and safely cut the drop-down door seal to size, being sure not to remove more than what the manufacturer specifies.

5. File down the side of the seal you cut, making it as smooth as possible.

6. If the door does not already have a groove to suit the seal dimensions, you will need to router out the bottom of the door to the size of the drop down seal, clearing any chips and dust from the groove.

7. On the opposite end to the actuator button, pull back the gasket and use a power/hack saw to cut down the aluminium sections to the manufacturers requirements to allow for the end plates.

8. Push the gasket back into position and cut to length with a sharp knife.

9. Position the seal into the groove, ensuring that the actuator button is on the hinge side of the door.

10. Mark each of the end plate positions on the edges of the door (if necessary). Cut out with a sharp chisel or router for round end plates.

11. Screw on the end plates and slide the seal into the groove.

12. Re-fit the door leaf and test the drop down seal by opening and closing the door, observing its operation. Adjust the seal accordingly.

Fitting instructions may vary depending on the drop seal manufacturer and the model. It's important to thoroughly read through the fitting instructions upon installation.

Looking for more information on fire door seals? Fire Seals Direct can help

A drop-down seal for fire doors is one of the easiest and most effective ways of stopping the spread of smoke under the door. Get in touch with our team and we’ll be happy to help improve your fire safety with advice about drop-down seals and their installation. You can reach out via our live chat feature or email us at [email protected].