Do I need to fit a threshold seal - and if so, why?
Watch our quick video where our Fire Safety Consultant answers this common query for you here.
BS 9999 (an Approved Document to the Building Regulations for England & Wales) states that if a fire rated door has a gap of over 3mm at the threshold, then you do need to fit a threshold seal. It's very difficult to know before the door is installed whether the gap will be over or under 3mm, so we do always recommend fitting a threshold seal. There are other reasons for this too. It is often assumed that the threshold is a low-risk area, but extensive research has proven that this is definitely not the case - an unsealed threshold presents a major cold smoke hazard. That is why undercutting the threshold of a door leaf to provide extra ventilation is extremely risky too, both in practice and principle. Threshold sealing is also essential for acoustic containment, as an acoustic sealing system will only truly be effective if it incorporates every gap around the door, and that includes the threshold. For more information on our threshold seals, please refer to our door bottom seals or drop seals.
I've heard about Document E - but how does it relate to doors?
The revisions to Approved Document E to the Building Regulations for England and Wales came into effect on 1 July 2003. From that date, all planning applications requiring Building Control approval, and work carried out under Building Notice procedures, has to comply with the revised regulations.
Much of Document E relates to the acoustic performance of floors, ceilings and walls. However, for the first time, the acoustic performance of door assemblies in a number of situations is also specifically detailed.
Requirement E1 states that: “Dwelling-houses, flats and rooms for residential purposes, shall be designed and constructed in such a way that they provide reasonable resistance to sound from other parts of the same building and from adjoining buildings.”
Document E also goes on to give specific guidance about the acoustic performance of doorsets: “Ensure that any door has good perimeter sealing (including the threshold where practical), and a minimum mass per unit area of 25kg/m2 or a minimum sound reduction index of 29dB Rw (measured according to BS EN ISO 10140-1:2016
and rated according to BS EN ISO 717-1:2013
). The door should also satisfy the Requirements of Building Regulation Part B – Fire safety.”
Requirement E4 covers acoustic conditions in schools, and incorporates Building Bulletin 93 as the recommended way of meeting the requirements. BB93 requires an acoustic performance for doorsets of 30dB Rw, and for music rooms, 35dB Rw.
Lorient's recommended sealing systems are specifically designed to enable these requirements to be met. It is important to remember that, while Document E says the threshold should be sealed “where practical”, extensive testing has proven that it is essential to do this in order to achieve the required level of acoustic performance.
For more information please download our Acoustic Sealing Systems for Door Assemblies brochure.
I need to achieve the highest acoustic rating possible on a standard door, can you help?
Our recommended acoustic seals will certainly help you get the best acoustic performance possible from the door assembly you have - but it's important to remember that no sealing system will improve the acoustic performance of the door leaf itself. Every door leaf will have a maximum acoustic performance, which will have been determined by testing the door construction with all the gaps around the edges filled (caulked). Many combinations of our seals have been proven to maintain a door leaf's acoustic performance to the same level as if the gaps were filled, and that's the best acoustic performance you will be able to achieve.
Some of our recommended solutions are as follows - please click on the links to product page links for more information:
For fire rated doors, our DS or Finesse™ combined acoustic, smoke and fire seals - the complete solution in one seal. Both the DS and Finesse™ have been proven to achieve an acoustic performance of 31dB Rw on a standard architectural solid door core, when tested in conjunction with a Lorient LAS8001 si drop seal.
For non-fire rated doors, we would always recommend our Batwing® acoustic and smoke seal. It has also achieved 31dB Rw on a standard architectural solid door core, when tested in conjunction with a Lorient LAS8001 si drop seal.
Do remember it is essential to fit a threshold seal to complete the system. You may find it helpful to read our FAQ on threshold sealing.
To find out more about our recommended acoustic solutions, please refer to our Acoustic Sealing Systems for Door Assemblies brochure. This also contains more information about how doors are tested, and the acoustic performance of various types of standard door construction.
We also offer a CPD seminar, entitled “Performance Door Design: The Basics of Sound Reduction”. Please visit our CPD Seminars page for more information.
I need to fit a glazing panel into a door that also needs to provide acoustic performance. How can I do this?
This won't be a problem, provided that thick enough glass is used, with an appropriate sealing system, and the size of the aperture is limited. Conventional “Georgian Wired” glass has been tested in conjunction with our System-36/6 PLUS glazing gasket, and this provides optimum acoustic performance for most types of door construction, including FD30 and FD30S doors. This will allow for up to 0.16m2 (eg, an 800mm x 200mm or 650mm x 250mm glazing panel) to be incorporated into the door without having a significant impact on the acoustic performance. If you wish to use other glass types or larger sizes, please contact our Technical Services team.
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.
- It can help to prevent weather ingress when used as part of a storm-guard system (such as our LAS3008).
- If you are sealing dissimilar surfaces (eg, carpet and vinyl), the threshold plate can cover the join to prevent both wear and tripping hazards. Our threshold ramps can also easily accommodate differences in floor heights, to make access easier for all.
- 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.
Please refer to our threshold plates and ramps for further details.
What standards and regulations relate to acoustic containment for doors?
Please click here to link to our Standards and Regulations section
I've heard that some seals on the market can achieve acoustic ratings of around 40-50dB Rw. Is that right?
You need to be very careful when you look at the acoustic rating of door seals. The door and the sealing system always work in combination, so the only way to really know how a seal will perform in practice is to test it on a full-size, working door assembly. Lorient always do that, and we'd suggest you ask for a copy of the full test evidence for any seal that claims to offer exceptionally high acoustic performance ratings. Do be careful if you find that any part of the door perimeter has been artificially caulked (filled) for testing purposes; or that the door assembly was smaller than it would be in reality; or that a non-standard door construction was used - any of these things may result in the seal being given an 'artificial' acoustic performance that it couldn't actually achieve in practice.
We're more than happy to provide specifiers and Lorient customers with a copy of our test evidence so you can make an informed choice!