Meet your legal obligations post 2019 NCC updates
Wondering about requirements for weatherproofing or the effects of penetrations?
Clarifying environmental impacts on roofing performance with your clients?
Philip Beveridge, experienced roofing consultant, presented the QBCC Tradie Talks this month. The recording and slides are now available:
Check out this summary of information (our take on the webinar's key points!) to save you time and money.
Professional and compliant roof design and installation avoids
Metal roofing defects are very common and are reported commonly to QBCC. Usually issues relate to
· Roofing selection/ material selections
· Poorly installed flashings etc
Repair costs can be high especially when it involves damage to surrounding building elements.
Environmental effects of roofing and walling is key– the successful selection of materials depends on environment and location of each project.
Design the roof right (success from the get go)
- Consider water / rainfall intensity (305 is a key measurement – recent decrease) so the overall roof run can be checked, and roof profile can be correctly designed to ensure capability.
- In the design stage it is especially important to consider the thermal efficiency and specify the colour early on - the Icanz book (free handbook) satisfies BCA Section J requirements.
NB: awning trusses in roof systems often require input from an engineer - more info from Timber Queensland here.
Builders – installation tips
1. Check penetrations and the effects these have on the roof profile.
2. Avoid penetration installation that obstructs water flow in a pan. If penetration does block a pan, tray flashings may be considered, though there are limitations. Using aluminium washers under the screw can be a work around.
3. Be across thermal movement / R values - worthwhile to double check manufacturers information and installation instructions.
4. Avoid failures- dirt build up means moisture can be retained so rust out will occur faster.
- Can collapse quickly with corrosion – check that air conditioning / condensation lines are correctly directed.
- Install to allow expansion eg leave a small gap
- Valley gutters- carefully consider at design stage as to whether and how appropriate gutters should be installed (roof pitch 12.5 %)
- Acceptable overflow measures – when box gutter is installed it must be fully sealed.
When lapping / joining, apply sealant throughout the line of intended fasteners then wipe off excess. Recommended resources - HB39 installation code of metal roofing and wall cladding table 8.1.4
· Sealed aluminium rivets are preferred (see figure 2.9 - sealant joints)
· Ribs – as a rule of thumb, min flashings cover two ribs as absolute minimum
· Flashings – “if you can draw it, they can fold it!”– make sure the shape suits the position to minimise gaps and holes.
– more common than timber –
Installation options- hazards and solutions
- Consider the location of additional battens eg roof traffic/ solar installations - consider someone cleaning out gutters and where they might walk
- Apply knowledge of bushfire considerations and current standards
- If roof profiles are upgraded, batten upgrade must be designed to suit
- Fastener types - roofing screw selection chart – use quality screws and consider the thickness/ material screw is entering.
Designers- looking for further clarification around roof design? Further details in BA&A’s previous post.
Builders- looking for QBCC’s revised standards and tolerances guide? See roofing related resources p 31