FIRE RESISTANCE Design Considerations

TI-1002

1 Introduction When developing a timber fire resistant doorset, it is very important to consider factors of the design that will influence:

• Production – can the door be manufactured consistently and cost-effectively?

• Performance – will the door meet the required performance levels?

• Coverage – will the tested design allow suitable assessed coverage of a range of product configurations?

Once the door has been manufactured and tested it can be very difficult and costly to alter the design in order to achieve a change in production, performance or coverage.

2 Production A door design may offer high performance but if the production is difficult, time-consuming, costly or will mean the product is not appropriate for its’ end-use application, the door is unlikely to be useful or saleable.

Factors to consider include: 2.1 Raw materials

• Availability • Cost

• Suitability e.g. the consistency of material properties

• Sustainability i.e. has the timber supply chain been certified (e.g. TRADA-Trak – FSC or PEFC)?

2.2 Manufacture A simple method of construction can reduce the risk of mistakes, increase the consistency of performance and make the product more commercially viable. 2.3 End-use application The door must be operable by the people intended to pass through it while still offering fire resistance performance. For example, if the door is designed to be used by the elderly or children it must be easy to open, so a very heavy door leaf, although offering the specified fire resistance performance, may not be appropriate.

3 Performance Testing should be carried out to British (BS) or European (EN) standards by a suitably accredited test laboratory. In the UK, laboratories should be accredited by UKAS. The following factors will impact upon the fire resistance performance achieved by the doorset under testing. For higher performance doors (e.g. 90 or 120 minute), these considerations are particularly important, as the scope for variation and inter-changeability tends to be limited.

3.1 Size During a fire resistance test, a doorset will have a tendency to distort and bow due to dehydration. The larger the door the greater the level of distortion. Once the door leaf bows out of the door frame reveal, failure of the complete doorset will occur. It is important to consider a method for controlling door edge distortion. For timber doors, the intumescent seals around the door edge are not only used to fill the gap between door and frame, but also to apply a force to the door to inhibit the distortion of the leaf. 3.2 Adhesives For fire resisting doors of a composite nature (i.e. made up of a number of components), the choice of adhesive (glue), preparation of the surfaces and gluing procedure is vital to maintaining an effective bond and sustaining performance. Adhesives with equivalent ‘cold state’ performance may not perform in the same way in a fire scenario. 3.3 Glazing All aspects of the glazing detail are crucial, including: glass type, intumescent specification, fixing tape, quality of timber for glazing beads and method of installation. Therefore the glazing system must have been tested in a similar door. 3.4 Hardware/Ironmongery The inclusion of metal into a timber doorset, will potentially reduce the performance of the door leaf because of the increased heat transfer. Any items of essential ironmongery (hinges, door closers, latches and door selectors) or non-essential ironmongery (kick plates, push plates, signs and pull handles) which have to be morticed into the doorset are highly likely to require testing. Door edge mounted hardware will interrupt the door edge seals and, consequently, additional intumescent will often be needed to protect these areas of vulnerability.

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4 Coverage (Assessments) In order to make the most of your test, it is advisable to provide a specimen that not only meets the immediate requirements of a particular project, but may also offer coverage of a range of products if used as the subject of an assessment. Test reports only relate to what has been tested and allow very few variations. Changes to a construction tested under the British or European standards will either require another fire test or an assessment. An assessment is a desktop study undertaken by an experienced fire consultant that allows variations from a tested design. The nature and scope of any variations will largely depend on the size and configuration of the tested specimen.

4.1 Size If the result of the fire resistance test exceeds the required period of integrity, it may be possible to increase the size of the tested leaf by applying established rules of assessment. This will allow for larger leaves to be used in future projects. 4.2 Configuration The doorset successfully tested should cover as many design variations as possible. The basic rules which control the range of designs covered by the tested (and subsequently assessed) doorset are summarised below. Steel doorsets have different requirements and a fire consultant should be contacted to determine the test programme. The guidance given below applies to BS EN 476: Part 22 only. If a BS EN 1634-1 test program is Required, seek advice from Chiltern International Fire.

1) Latch Unlatched covers latched Latched does not cover unlatched

2) Leaves Double covers single or unequal Single does not cover double or unequal

3) Overpanel Overpanel covers no overpanel No overpanel does not cover flush overpanel (but transomed panel can be supplied)

4) Glazing Glazed covers unglazed* Unglazed does not cover glazed*

5) Meeting stile Rebated covers flush Flush does not cover rebated

OR

OR

Unequal covers single or double

*Unless glazing makes up the majority of the door’s surface area

*Sometimes a small glazing aperture may be permitted

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IMPORTANT NOTE: The basic rules outlined above cannot be used to show compliance with Building Regulations or any other requirements without a formal assessment written by a professional fire safety consultant.

Chiltern International Fire Stocking Lane . Hughenden Valley . High Wycombe . HP14 4ND . UK

t +44 (0) 1494 569800 f +44 (0) 1494 564895

e fireresistance@chilternfire.co.uk w www.chilternfire.co.uk

5 How can Chiltern Fire help? Chiltern International Fire is a UKAS accredited test laboratory offering fire resistance testing and assessment. In addition, we offer a comprehensive range of support services to assist manufacturers by:

• advising on fire door design

• developing a programme of testing to cost-effectively cover a range of products

• witnessing the test to explain performance and reasons for failure, offering possible solutions where required

• manufacturing and installing test specimens using our on-site workshop facilities.

6 Q-Mark fire door certification schemes Q-Mark offers the ultimate assurance for specifiers, purchasers and end-users that products will perform. Manufacturers must meet rigorous testing and approved quality management requirements. Checks are made on an on-going basis through regular audit testing and inspections by auditors with specialist knowledge.

7 Further Information Chiltern International Fire offers a number of ways of finding out more about fire testing and assessments: Website www.chilternfire.co.uk Technical Information sheets TI-0801: Fire Resistance - Testing, Assessment & Certification TI-1004: Fire Resistance - Service Penetration Seals Testing TI-1010: Historic Buildings & Fire Safety TI-1014: Fire Doors for the Health Sector DVD Fire Resistance Testing Explained Seminars Timber Fire Doors Explained (includes a full-scale fire resistance test)