Roofing material is to be determined based on the Whole of Life approach to ensure that an appropriate, robust and durable material, suitable for the application is used.
Materials Acceptable to University
New roofs should be Colorbond coated to match or be supplementary to existing or adjacent roofs.
Base material is to be selected to suite the local environmental conditions with all base material being at least Zincalume sheet, use Colorbond XSE where additional corrosion resistance is required.
Provide blanket insulation under all metal roofs to exceed regulatory thermal requirements as well as reduce sound transmission.
Membrane type roofing is not recommended due to their maintenance requirements and is only to be used where specifically approved. Types of membrane roofing, finishes and details will require to be submitted to the MQP.
Roof design and Access for maintenance
Within the design provide access for the maintenance of roof surfaces, gutters and down pipes.
Where roof gutters are within 4m of an adjacent ground level that is suitable for positioning a ladder then roof access may not be required, subject to facilities maintenance agreement.
Subject to site specific WHS considerations, portable ladders may be suitable for use on 1 storey buildings.
The methods of maintenance are to be identified and agreed to by MQP prior to documentation, to ensure the provision and proper co-ordination of maintenance requirements.
Safety measures for servicing of roof-top plant and equipment, including ladders, ladder fixing points, walkways and handrails around roof zones, must be indicated at design phase. The design is to meet the Workcover WHS safe access requirements.
Negative pressure (or suction) can have a significant impact on roofs causing the roof to be lifted off the structure during high /extreme wind events. The risk increases as the roof slope decreases, with low pitch roofs incurring very severe negative pressure problems.
Eaves projections are particularly vulnerable with both the suction effect on the upper surface and positive pressure below.
To reduce the effects of negative pressure it is important for Roof fixing to be included as per Manufacturer's recommendations for the appropriate Site Wind category.
Flashing and Accessories
- Roof flashings are to be constructed from material to match the roofing and adjacent material.
- All copings, ridging pieces and similar are to be securely fixed and adequately supported to hold their shape.
- Detail complex penetrations of the roofing by pipes or ducts where unavoidable.
- Upstand of apron flashings to be 150mm minimum.
- Overflashings to lap a min. of 75mm.
- Slope flashings away from the upstand. Project side flashings over two ribs and lap flashing joints in the direction away from the prevailing wind.
- Provide for expansion and contraction at all flashings.
- Roof guttering are to be outside the line of the external walls so that any overflow will remain outside the envelope of the external walls. Concealed gutters behind parapet walls, or box gutters between roof slopes should be avoided.
- All roofing must be of continuous sheets wherever possible, complying with the minimum pitch requirements noted in roofing and to Australian standards.
- This need not be a design restriction, as many opportunities are apparent in the visual expression of roof drainage and climatic control systems, pertinent to our environment.
- Roof gutters are to be designed to satisfy rainwater flow recommendations in relevant Australian standards and the NCC.
- Eaves gutters are to be of half round powder coated aluminium or Colorbond coated zincalume steel of approved profile.
- Each gutter is to be constructed to overflow outside the building in the event of a blockage in either the downpipe(s) or the gutter itself.
- Gutters are to be laid with a minimum fall of 1% to outlets.
- Gutter linings are to be constructed of 0.55mm 304 grade stainless steel.
- Where Box gutters are permitted, they are to be designed and constructed to ensure that there are no "blind" box gutters which have no outlets except downpipes.
- Gutters and downpipes are to be constructed to ensure ease of cleaning and freedom from blockage by leaves, hail, etc. The minimum dimensions of any box gutter are to be 450 x 150mm.
Headers and Downpipe Entries
To facilitate cleaning of downpipes, include metal headers at gutter level and open grated drainage sump upturns at ground level with downpipes stopped 200mm above drain opening.
Ensure that grate to drainage sump can not be removed by unauthorised persons.