Fire and Acoustic Rating
Fire Rating
· There are two systems for fire rating Posi-STRUT floor truss systems: The GBPS system. The Gib board is fixed to a 600mm grid of ceiling strapping and nogging.
· The GBUC or Winstone Universal Ceilings system. More layers of Gib Board can be fixed directly to the underside of the Posi-STRUT trusses. Refer to the 'Gib Board Fire Rated Systems' manual published by Winstones Wallboards Ltd.
Intertenancy floors usually require both fire and sound rating. The GBDFA and GBSCA systems are suitable for use with Posi-STRUT trusses. Refer to the 'Gib Intertenancy Sound Control Systems' manual published by Winstones Wallboards Ltd.
These systems are substantiated by tests performed by and opinions provided by the Building Research Association of New Zealand, Winstone Wallboards Ltd and Marshall Day Associates.
The GBPS30, GBPS60, GBPS90 Systems
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Specification Fire rating Lining Requirements GBPS30 30/30/30 (30mins) 1 layer 12.5mm Gib Fyreline GBPS60 60/60/60 (60mins) 1 layer 16mm Gib Fyreline GBPS90 90/90/90 (90mins) 2 layers 16mm Gib Fyreline
Floor Framing
The fire rated system is for Posi-STRUT floor trusses using Posi-STRUT PS20, PS25, PS30 or PS40 webs with 90x35, 90x45, 75x50 or 100x50 timber chords. Trusses should not be spaced at greater than 600mm centres. 75x40 ceiling strapping at maximum 600mm centres should be fixed to the bottom chords, perpendicular to the orientation of the trusses. 75x40 nogs parallel to the trusses should be fixed to the bottom chord of the trusses.
For the GBPS30 specification the ceiling strapping can be omitted, with the Gib Fyreline fixed directly to the underside of the trusses and to 75x40 nogs at 600mm crs.
Flooring
The flooring shall be 20mm thick particle board. The flooring shall be nailed to the Posi-STRUT trusses with 60mm x 2.8mm galvanised jolt head nails at 150mm centres to all sheet edges and 300mm centres to intermediate trusses.
Ceiling Lining
Ceiling lining as shown in above table. Gib Fyreline shall be fixed at right angles to the floor trusses. For GBPS90 the joints of the second layer are to be offset 600mm from the first layer. All joints must occur on joists, solid strutting or nogs.
Fixing
Ceiling sheets shall be fixed with:
- either 50mm x 2.5mm galvanised Gib Clouts at 150mm centres around the perimeter of each sheet and double fixed at 200mm centres across each batten or nog. Double fixings approximately 50mm apart.
- or 50mm x 7g bugle head gypsum drywall screws at 150mm centres around the perimeter of each sheet and fixed at 200mm centres across each batten or nog.
For the GBPS90 system, the second layer of Gib Fyreline should be fixed with:
- either 75mm x 3.15mm galvanised Gib Clouts at 150mm centres around the perimeter of each sheet and double fixed at 200mm centres across each batten or nog. Double fixings approximately 50mm apart.
- or 75mm x 8g bugle head gypsum drywall screws at 150mm centres around the perimeter of each sheet and fixed at 200mm centres across each batten or nog.
Corners
The internal angle between ceilings and walls shall be protected by Gib Cove fixed with Gib Cove adhesive, or with corners filled and taped in accordance with Winstone Wallboards Ltd? 'Gib Board Stopping and Finishing Systems - 1992'
Jointing
All joints must occur on joists, solid strutting or nogs. To achieve the FRR and strong flush joints for painted surfaces, the jointing and finishing of joints and fastener heads must be carried out in accordance with Winstone Wallboards Ltd? 'Gib Board Stopping and Finishing Systems - 1992'
The GBUC30, GBUC60, GBUC90 Systems
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Specification Fire Rating Lining Requirements GBUC30 30/30/30 (30mins) 1 layer 16mm Gib Fyreline GBUC60 60/60/60 (60mins) 1 layer 16mm and 1 layer 12.5mm Gib Fyreline GBUC90 90/90/90 (90mins) 2 layers 19mm Gib Fyreline
Floor Framing
The fire rated system is for Posi-STRUT floor trusses using Posi-STRUT PS20, PS25, PS30 or PS40 webs with 90x35, 90x45, 75x50 or 100x50 timber chords. Trusses should not be spaced at greater than 600mm centres. Ceiling strapping and nogs are not required.
Flooring
Any flooring material that meets structural criteria for strength and serviceability may be used.
Ceiling Lining
Ceiling lining as shown in above table. The first layer of Gib Fyreline shall be fixed at right angles to the floor trusses. Where a second layer is required the joints of the second layer are to be offset 600mm from the first layer. All sheet end joints must occur over solid framing.
Fixing
First layer of Gib Fyreline - 40mm x 6g bugle head gypsum drywall screws or 50 x 2.5mm galvanised Gib Clouts.
Second layer Gib Fyreline - 50mm x 6g bugle head gypsum drywall screws or 60 x 2.7mm galvanised Gib Clouts.
Fixing centres: At 200mm centres along each intermediate truss, and at 200mm centres to framing members at sheet end joints.
Corners
The internal angle between ceilings and walls shall be protected by Gib Cove fixed with Gib Cove adhesive, or with corners filled and taped in accordance with Winstone Wallboards Ltd? 'Gib Board Stopping and Finishing Systems - 1992'
Jointing
All fastener heads in the second layer to be stopped and all sheet joints in the second layer to be tape reinforced and stopped in accordance with Winstone Wallboards Ltd? 'Gib Board Stopping and Finishing Systems - 1992'
Posi-STRUT Truss Selection
Using a fire rated ceiling system places a higher load on the Posi-STRUT floor trusses because the Fyreline is heavier. Use the following table to select which selection chart to use in the Posi-STRUT manual.
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Design Floor Live Load to Use in Selection Charts
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Floor Loading kPa Fire System 1.5 2.5 3.0 GBPS30 1.5 2.5 3.0 GBPS60 2.5 2.5 3.0 GBPS90 2.5 2.5 SD GBUC30 1.5 2.5 3.0 GBUC60 2.5 3.0 SD GBUC90 2.5 3.0 SD
SD denotes special design, contact the MiTek Design Office
Acoustic Rating
Based on testing performed by Winstones Wallboards Ltd and an opinion provided by Marshall Day Associates (96114RA), the specification for intertenancy floors is as follows:
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Specification STC IICBare Floor IIC Carpet FRR (Fire rating) Lining Requirement to underside of the support frame (Gib Fyreline) GBDFA30 56 44 71 30/30/30 2 layers 12.5mm GBDFA60 55 46 72 60/60/60 2 layers 12.5mm GBSCA30 57 46 72 30/30/30 2 layers 12.5mm GBSCA60 55 43 72 60/60/60 1 layer 12.5mm & 1 layer 16mm GBSCA60a 58 46 72 60/60/60 1 layer 12.5mm & 1 layer 16mm
Notes: STC = Sound Transmission Class
IIC = Impact Isolation Class
The GBDFA system uses a 'direct fix clip', screwed onto the Posi-STRUT at 1200 max crs. This supports steel furring channels. We recommend that the direct fix clips are staggered in order to spread the weight of the ceiling across all trusses.
The GBSCA system uses a suspended ceiling system.
Further details of the fire and acoustic systems can be found in the 'Gib Board Fire Rated Systems' manual and the 'Gib Intertenancy Sound Control Systems' manual.
