The purpose of a drop seal

When it comes to acoustic or fire / smoke-rated doors, whether in residential or commercial spaces, there is a growing need for innovative solutions that help contain sound and most importantly smoke & fire at the threshold of the door. One such solution that has gained popularity in recent years is automatic drop seals for doors. We discuss the benefits here...

What is an automatic drop seal?

Automatic drop seals are devices that are installed at the bottom of doors – typically they are concealed within a grooved rebate at the bottom of a timber door leaf, but they can be face-fixed or semi-mortised too. The seal drops automatically when the door is closed to form a firm seal with the floor, lifting when the door is opened to ensure the door operation is unimpeded. It’s crucial that the sealing system fitted to a door assembly has minimal effect on the opening and closing operation of the assembly.

Do you need power to operate drop seals?

No, our drop seals feature a high-efficiency mechanism, which lifts the seal clear of the floor as soon as the door is opened by a few millimetres, resulting in lower door operating forces. Automatic drop seals are self-leveling when the door is closed, ensuring a consistent and effective seal every time.

What are the benefits of automatic drop seals?

  • Acoustic containment: Effective sealing of the threshold gap is absolutely essential to meet the performance requirements for acoustic doors. A significant benefit of automatic drop seals is their ability to provide acoustic containment at the threshold, which can be a commonly overlooked area. When used in conjunction with an appropriate acoustic sealing system, the seals help to contain sound – making them ideal for doctor's surgeries, offices, schools, hotels etc. Refer to door manufacturers' acoustic test evidence.
  • Smoke containment: A study of smoke behaviour clearly shows that it is not sufficient to seal only the tops and sides of doors. Both cold smoke and sound will transfer to an adjacent compartment through the gap at the threshold. Fitting a drop seal can provide protection against smoke when coupled with an effective perimeter seal.
  • Energy containment: Our seals are tested for air tightness under BS 476: Pt. 31.1: 1983 – this makes a positive contribution to thermal containment between spaces within a building, as well as for external doors; helping in the efficient energy management of a building.
  • As well as sound, smoke, fire and energy containment, drop seals can provide protection against insects, light transfer and dust.

If I fit a drop seal, do I need to fit a threshold plate too?

A threshold plate is a good idea for several reasons. It will help to ensure a good seal is maintained at the threshold, by giving a firm surface for the drop seal to rest against. If you are sealing dissimilar surfaces (eg, carpet and vinyl), the threshold plate can cover the join to prevent both wear and tripping hazards. If your floor surface is particularly liable to wear and tear in places below the door (eg, a high level of traffic, or over a carpet that may become compressed over time), then a threshold plate will help to prevent these uneven areas affecting the threshold sealing.

Do you offer retrofit drop seals?

Yes we do - we offer a vast range of face-fixed options from drop seals with curved cover plates to heavy-duty options. The LAS80002 si drop-seal provides an elegant solution to retro-sealing at the threshold. It is easy to fit, can be cut-to-size (refer to fitting instructions) and has a maximum drop of 13mm.

What is your best-selling drop seal?

Our best-selling drop seal is the LAS8001 mortised drop seal, trusted by many - it’s backed by comprehensive test evidence for acoustics (up to 39dB), smoke and fire; it’s also been cycled 1 million times for durability testing.