Encasement of structural steel.
Planning - key factors
FireCase steel encasement is suitable for protecting structural steel sections with a section factor A/V (Hp/A) up to 260m-1, calculated on the basis of box protection to three or four sides as required. It will protect universal column and beam sections described in BS 4: Part 1, and many joist and castellated beam sections.
The designer should follow the procedure below to determine the thickness of cladding required:
1. Ascertain whether protection is required on three or four sides of the section.
2. Find out what period of fire resistance is required.
3. Refer to the WHITE BOOK A/V (Hp/A) Tables 2 - 4. Locate the steel section to be protected, listed by its size and mass per metre, and read off the section factor A/V.
4. Refer to Tables 5 - 8. Locate the A/V value on the vertical scale on the appropriate table. Read across the chart to the column relating to the period of fire resistance required and read off the designated thickness of the relevant cladding required to form the encasement.
5. Select the type of board to be used.
For castellated sections and cellular beams please refer to the Association for Specialist Fire Protection publication, ASFP Yellow Book - ‘Fire Protection for Structural Steel in buildings’ for guidance, available to download from www.asfp.org.uk
For improved durability and impact resistance, the outer layer of Gyproc FireLine can be replaced with a layer of 15mm Gyproc DuraLine.
Partitions and wall linings may be fixed directly to the Glasroc F FIRECASE cladding as long as:
1. The fire resistance requirement of the partition is 60 minutes or less.
2. There are no special requirements for pressure resistance, e.g. around lift shafts.
3. There are no special loading requirements, i.e. Heavy Duty or Severe Duty as defined in recognised partition performance specifications (e.g. BS 5234). See WHITE BOOK Construction details – 9.
Where these criteria are not met, the partition framing must be suitably fixed to the structural steel section, through the Glasroc F FIRECASE cladding. Where the partition abuts the web of the structural steel, a suitable steel nogging must be provided. See WHITE BOOK Construction details – 10.
Where steel section web dimensions exceed 600mm, additional support will be required for the cladding. Please contact the British Gypsum Drywall Academy for guidance.
Lightweight tiles can be applied using conventional tile adhesives without pre-treatment of the Glasroc F FIRECASE.
Refer to WHITE BOOK section 13 – Finishing systems and decorative effects.
Glasroc F FIRECASE joints can be treated using Gyproc Joint Tape bedded in Gyproc Joint Cement. External angles / corners can be reinforced using Gyproc No-Coat Ultraflex 325 bedded in Gyproc Joint Cement.
If a plaster finish is required, joints should be reinforced and Thistle Board Finish, Thistle Durafinish or Thistle Multi-Finish applied. Refer to WHITE BOOK section 13 – Finishing systems and decorative effects, Plaster skimming.
Jointing and finishing is not a requirement of meeting the specified fire resistance. Board joints / abutments must be a flush fit.