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1. How do I make fire rated door frames?
2. How do I make and sell a fire rated doorset?
3. Is there a Publicly Available Specification (PAS) for constructing fire rated doorsets?
4. Can I use solid MDF/timber panels for fire rated doorsets?
5. Is a 10mm x 4mm intumescent seal for 30 minutes integrity and a 20mm x 4mm intumescent seal for 60 minutes integrity adequate?
6. Can a test laboratory provide me with copies of test/assessment reports?
7. How can I upgrade existing doorsets?
8. Traditionally a 20 minute fire doorset comprised a 25mm doorstop, no intumescent and a 30 minute blank, is this still acceptable?
9. Can I use rising butt hinges as a closer for my fire door?
10. Do any timbers have an inherent spread of flame classification? And how do I treat timbers for class 1/class 0?
11. Can intumescent strips be over-painted?
12. Can I, and how do I, put glass into my fire door? Do I have to be an approved installer?
13. What qualifications do I need to install a fire door?
14. If the door does not fit, can it be resized?
15.What is the recommended gap between leaf edge and frame for a fire rated door?
16. Can a 60 minute doorset be hung in a softwood frame?
17. Can I fit a letter plate or eye viewer to my fire rated door?
18. Can kick/push plates be fitted to the face of the fire door?
19. Can I groove into a fire door to simulate a panelled design?
20. Can I interrupt the perimeter intumescent/smoke seals with hardware?
21. What are the benefits of third-party certification?
1. How do I make fire rated door frames?
There is no such thing as a stand-alone, fire rated door frame. The frame can only be considered as ‘fire rated’ when it is machined in accordance with the tested details and installed, with the appropriate door, as a complete doorset. Therefore, if the frame and door leaf are to be made by different manufacturers, or the frame is to be made on site, its specification must match exactly that of the complete fire tested doorset.
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2. How do I make and sell a fire rated doorset?
In order to sell a door as a fire door there needs to be sufficient test evidence in place to justify the design. There are three main options to achieve this:
1. Direct testing of the doorset design, which involves testing the door at a UKAS- accredited laboratory to the relevant BS or BS EN test standard (BS 476: Part 22: 1987 or BS EN 1634 -1 2000)
2. Having an assessment produced for the doorset design by qualified fire engineers using existing fire test data in lieu of a fire test
3. Using a door manufacturer’s proven door blank and global assessment data to produce fire-rated doorsets.
Each method is equally valid for proving a fire door’s performance. To select the most appropriate method for you, it is advised that the relevant test laboratory is contacted so that lead times, costs and benefits can be discussed with qualified personnel.
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3. Is there a Publicly Available Specification (PAS) for constructing fire rated doorsets?
There are no PAS’s or Standards for manufacturing fire rated doorsets. Typically, a fire rated doorset should:
- Be in accordance with a specification or design which has been shown by test to be capable of meeting that performance; or
- Be assessed from test evidence against appropriate standards, as meeting that performance.
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4. Can I use solid MDF/timber panels for fire rated doorsets?
No, not unless there is suitable test evidence that a specific solid MDF/timber panel in a particular doorset design has achieved the required rating. A more robust specification for panels is a composite construction, with a proven non-combustible core faced either side by a required minimum thickness (prescribed in assessment) of timber or MDF.
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5. Is a 10mm x 4mm intumescent seal for 30 minutes integrity and a 20mm x 4mm intumescent seal for 60 minutes integrity adequate?
Whilst it is generally true that larger intumescent strips are used for higher integrity periods, the intumescent specification for the door must be as tested or assessed for that particular doorset. This is the case for:
- the size of the intumescent seal
- the location of the seal
- the type of seal
NB: The type of seal is also particular to the manufacturer, as different manufacturers’ seals do not perform comparably, even if they are of the same generic type, e.g. graphite. It is for this reason that interchanging between different seal types and/or manufacturers is not permitted, unless there is test evidence available to demonstrate otherwise.
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6. Can a test laboratory provide me with copies of test/assessment reports?
No, not without the written permission of the test sponsor, as all door manufacturers’ test and assessment data is held in confidence by the relevant test laboratory.
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7. How can I upgrade existing doorsets?
There are numerous methods for upgrading existing doorsets to enhance their inherent fire resistance, although every upgrade is specific to each doorset and consequently may not necessarily be appropriate for another design.
The only way to ensure that the most appropriate method is chosen - and to have the enhanced integrity performance underwritten - is by commissioning a site survey by a qualified fire engineer. The relatively large number of components that make up a fire rated doorset are integral to its performance and a comprehensive knowledge of these components is needed, e.g:
- Whether the door can be upgraded to the required integrity
- What the most appropriate upgrading measures are
- If there are other issues that may negate the performance of the door, such as sidelights or over panels
- How to address glazing, panelling, ironmongery, intumescents, core type etc.
- If proprietary products are to be used, is there suitable fire test evidence and does it match the design of door being upgraded, for example in terms of panel sizes?
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8. Traditionally a 20 minute fire doorset comprised a 25mm doorstop, no intumescent and a 30 minute blank, is this still acceptable?
Prior to 1972 the British Standards prescriptively defined how to construct a fire doorset and this included using 25mm doorstops. Since then the standards have been changed and the method of proving performance is by independent testing. For economic reasons, manufacturers generally test to achieve 30 minutes and sell the same product for 20 minute applications. Unless there is specific test evidence, 20 minute fire doorsets still require the intumescent strips tested for 30 minutes to be fitted. Purchasers should satisfy themselves that acceptable evidence exists, rather than working to out of date prescriptive solutions.
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9. Can I use rising butt hinges as a closer for my fire door?
Approved Document B cites rising butt hinges as acceptable for use on fire resisting doorsets, providing there is suitable test evidence available. To the best of our knowledge, there is no supporting fire test data for the use of rising butt hinges and this, coupled with their known limitations, lead us to recommend that such hinges are not used with fire resisting doorsets.
In order for rising butt hinges to operate effectively, the leaf head or frame head has to be chamfered, which means there will be the correct leaf to frame gap on one side of the door, but too large a gap on the other. If the gap is too large, the intumescent seal will not react as intended and this may therefore negate the performance of the leaf.
In some instances both the leaf and frame head may be simultaneously chamfered, giving rise to a different but potentially serious problem whereby the reacting intumescent seals in the head force the leaf open due to the direction of flow and pressure from the reacting material.
Another problem with rising butt hinges is that they rely on gravity to close the door over the latch and it is quite common for pressure differentials within a building to prevent the hinges from doing so. This can then lead to the door ‘bouncing’ on its latch and not fully closing within its frame reveal, thus failing to function as an effective fire resisting doorset.
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10. Do any timbers have an inherent spread of flame classification? And how do I treat timbers for class 1/class 0?
Spread of flame and fire resistance are two quite separate performance characteristics. Fire doors must prove their fire resistance rather than spread of flame performance.
In Approved Document B, the typical performance rating for untreated timber or plywood with a density of more than 400kg/m3 is class 3 and therefore any untreated timber will need test evidence to prove that it has a higher rating.
In general, timber will need treatments to achieve the higher ratings. It is recommended that a timber treatment specialist is consulted to ensure that the most appropriate method is chosen.
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11. Can intumescent strips be over-painted?
Most manufacturers of intumescent seals recommend that ideally intumescent strips should not be painted over. For further clarification contact the seal manufacturer for supporting evidence and advice.
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12. Can I, and how do I, put glass into my fire door? Do I have to be an approved installer?
Not all fire rated doorsets can tolerate glazing and it is therefore essential to check the test evidence/assessment data for that door. If the door can accept glazing then it is of paramount importance that the exact guidelines are followed, as apertures may need to be internally framed/lined with timber.
The following is an excerpt from ‘A Guide to Best Practice in the Specification and Use of Fire Resistant Glazed Systems’ written by the Glass and Glazing Federation (GGF).
‘The fundamental Golden Rule
Fire resistant glass must only be used as part of a fire resistant glazed system – which includes the glass, the glazing seal, beads, fixings and frame. All the essential components of such a system must be compatible under fire conditions, and the performance must be referenced to appropriate and relevant test evidence.’
There is currently no legal or statutory requirement to be certified to glaze fire resisting doors. However, it is recommended that anyone undertaking this type of work attends an appropriate training course specifically on glazing, or at the very least a general course that outlines the construction of these performance products. Attendance will also help provide evidence that the installer is competent. (Suitable third party certification can be obtained from a UKAS-accredited certification body).
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13. What qualifications do I need to install a fire door?
The British Standard that provides recommendations on the installation of fire doors is BS 8214: 2008 Code of practice for fire door assemblies. Whilst there is no requirement to be third party certified, becoming an approved installer is a good way of demonstrating competence and, more importantly, should guarantee that the installed doorset will perform for the intended period of fire resistance.
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14. If the door does not fit, can it be resized?
Resizing a doorset is not something that should be done without first contacting the manufacturer. Most door designs rely on components being of a minimum size in order to perform in a fire. Lippings are particularly important on typical flush door leaves – removing 3 or 4 mm can in some instances halve the depth of a lipping which could have a detrimental effect on the fire performance.
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15. What is the recommended gap between leaf edge and frame for a fire rated door?
The recommended leaf edge to frame gap specified in BS 8214: 2008 is 4mm on all edges. Intumescent seals are engineered to react within this size of gap to give optimum sealing and clamping performance.
It is through extensive testing of fire rated doorsets, together with knowledge of the pressure regime within a fire test, that a larger gap is permitted at the threshold of the door. There is negative pressure at the threshold during test conditions and so cool air is drawn in underneath the door. It is for this reason that there is unlikely to be a failure at the threshold and also why there is no need to fit a perimeter intumescent strip at this location (doorsets below 60 minutes performance). A larger gap at the threshold is also useful from a practical end use application for accommodating floor coverings. We recommend a gap of 10mm from the bottom of the leaf to the structural surround.
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16. Can a 60 minute doorset be hung in a softwood frame?
In practice it is very difficult to pass a 60 minute fire test using a softwood frame, simply because it chars more quickly than most hardwoods. For this reason dense hardwoods are usually used, but softwood would be permissible if it were supported by appropriate test evidence.
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17. Can I fit a letter plate or eye viewer to my fire rated door?
Fitting a letter plate or eye viewer will breach a fire rated doorset and has the potential to allow a direct passage for hot gases and flames. It is therefore important that:
- There is test/assessment data for the fire rated doorset to tolerate the hardware
- The hardware being fitted has been previously tested in a doorset of comparable construction
- The maximum height at which the letter plate can be fitted is adhered to (see below).
The test conditions of BS 476: Part 22: 1987, are such that the neutral pressure axis is at 1000mm from the threshold of the door (500mm in BS EN 1634 – 1 2000); below the axis the pressure is negative and above the axis the pressure is positive. This means that above the neutral pressure axis hot gases will be forced against the doorset and without supporting test data a letter plate fitted at this location may compromise the integrity of the doorset. The tested height of a letter plate relative to the neutral pressure axis is therefore an important constraint in limiting its location.
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18. Can kick/push plates be fitted to the face of the fire door?
It is usually permitted to face fix kick plates and push plates to a fire resisting door. We permit facing the door with metal to a combined maximum of 20% of the timber area of the leaf, provided that the metal face is surface fixed and does not wrap around any leaf edge or interfere with any essential intumescent seal. Above the 20% limit of timber surface area, or for any other condition, further test evidence must be generated. The reason for limiting the area of metal on a door is because when heated in the fire the metal will expand, while the wood will shrink, causing distortion. It can also act as a heat sink, thus accelerating char and erosion at localised areas.
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19. Can I groove into a fire door to simulate a panelled design?
Only if there is suitable test evidence for the door blank and if there is, the precise specifications are followed. The thickness of the door is crucial to its stability when subject to fire conditions. The timber on the fire side becomes dehydrated, which leads to the door distorting in towards the fire. The thinner the door, the quicker this happens - and to a greater extent. Grooving into areas of the door will leave localised weak spots and the door will not perform as expected.
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20. Can I interrupt the perimeter intumescent/smoke seals with hardware?
If there is a smoke requirement for the door and the smoke seal is interrupted by the hinge locations, it will be necessary to run another length of the seal alongside the hinge blade to maintain continuity. The intumescent seal position has to remain as tested and should not be re-routed to another position; doing so may negate the performance of the door. In placing the intumescent seal in a different location to that tested, the seal may not react as it did during testing. One possible consequence of this could be ineffectual sealing and clamping of the door leading to premature failure.
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21. What are the benefits of third party certification?
To achieve third-party certification manufacturers and installers will undergo stringent performance and production audits on an ongoing basis, to ensure that every product will provide the same levels of performance as that originally tested. Third party certification is undertaken by independent expert bodies and they will typically list accredited manufacturers and installers on their website. For example, a list of fire door manufacturers who are full members of the BM TRADA Certification Q-Mark scheme can be located at www.bmtrada.com, along with a list of registered installers.
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