Specifications

STANDARD SPECIFICATION - BUILDINGS
DPI REFERENCE TEXT - APRIL 2009
PAGE 17
ROOFING
7. ROOFING
7.1 GENERAL
Cross reference
Refer to the InsulationandSarking section for roof
sarking requirements.
7.2 MATERIALS AND COMPONENTS
Roof material
Formed from G550 steel (or G300 for curving) with
an AZ 150 Finish complying with AS 1397.
Protection: Protect the roof sheets from damage
during handling and storage and prevent damage
by moisture in stacked sheets.
Prepainted Steel
Prepainted steel sheet, factory nished with a
polyester nish to AS/NZS 2728.
Flashing material
Use material with the same nish and from the same
manufacturer as the roong sheets.
Thickness: 0.55mm BMT steel sheet.
Fasteners
Self-drilling screws: To AS 3566.1, complete with
washers and EDPM black, non conductive seals.
Corrosion resistance: To AS 3566.2.
• Tropical areas: Class 4
• Inland areas: Class 3
Exposed fasteners: Provide fasteners which are
prenished with an oven baked polymer coating to
match the roong material.
Fixings: Use only approved metal xings.
Roof lights
Type: As scheduled or shown on the drawings
and tted in accordance with the Northern Territory
Deemed to Comply standards.
7.3 INSPECTION
Notice - Witness Point
Witness Point: Give sufcient notice so that
inspection may be made of the substructure before
xing the roof sheeting.
7.4 ROOF STRUCTURE
Alignment
Check and adjust the alignment of the roof structure
before xing any sheets.
Battens: 2 mm maximum mismatch at abutting
ends.
Roof Plane: 5 mm per metre maximum deviation
across the battens from a plane parallel to the
specied roof slope.
7.5 METAL FASCIA & BARGE
Stratco 0.55 mm BMT prepainted steel 210 mm or
185 mm deep to suit the particular application.
Fixing: Fix to rafter ends with proprietary xing clips
in accordance with manufacturer’s instructions.
Provide corner trims, end trims and cappings as
required.
7.6 METAL ROOFING
Design and installation
Standard: To AS 1562.1.
Fixing: Fix the sheeting in accordance with the
Northern Territory Deemed to Comply standards.
Visible accessories
Provide material with the same nish as roong
sheets.
Eaves
Treat ends of sheets as follows:
Generally: Close off ribs at tops and bottoms of
sheets by mechanical means or with purpose-made
end caps.
Turn ends of pans up at tops and down into gutters
at bottoms by mechanical means.
Project sheets 50 mm into gutters.
Fit purpose-made ridge and eaves llers of closed
cell polythylene similar to Unisil.
Swarf
Remove swarf and other debris as soon as it is
deposited.
7.7 ROOF PLUMBING
Selection and installation of rainwater goods
Standard: To AS/NZS 3500.3.
Sealing: Seal fasteners and mechanically fastened
joints with silicone sealant.
Fixings: Use only approved metal xings.
Flashings and cappings
General: Flash projections above or through the
roof with two part ashings consisting of an apron
ashing and an over-ashing, with at least 100 mm
vertical overlap. Provide for independent movement
between the roof and the projection. Continue over
ashing to the roof ridge.
Wall abutments: Where a roof abuts a wall, provide
overashings as follows:
• Masonry or concrete: built into a 25 mm deep
raking sawcut.
• Planked cladding: Stepped.
Pipe Penetrations: Seal with a neoprene coupling
clamped to the pipe and xed to the prole of the
roof sheeting.
Proprietary Item: Dektite ashings by Deks-Thyer
Pty Ltd.
Colour: To match the roof sheeting.
In Concrete or Masonry: Turn 25 mm into joints or
grooves, wedge at 200 mm centres with compatible
material and point up.
Gutters
Generally: Prefabricate gutters to the required
shape where possible. Form stop ends, bends and
returns. Turn down into outlets. Provide overows
to prevent back-ooding.
Specifications March 2009.indd 17 11/03/2009 11:47:10 AM