Why Roof and Veranda Are Priced as Separate Jobs
A standard flat or skillion roof and a curved bullnose veranda use genuinely different products. Standard Custom Orb corrugated roofing is not designed to be curved — attempting to bend it will damage the profile. Bullnose verandas require Custom Blue Orb, which is factory-curved to a specific radius (minimum 300mm, or 400mm in Victoria) before delivery. This is also typically more expensive per lineal metre than flat roofing, due to the specialised forming process, which is why this tool costs each job independently rather than blending them into one figure.
Guttering & Downpipe Sizing
Quad profile guttering is used in roughly 60% of Australian installations and suits most roof styles. Half Round suits heritage and weatherboard homes, while Square Line is more common on contemporary builds. Downpipe spacing in this tool follows the practical trade rule of thumb of one downpipe per 10–12 metres of gutter run. For anything beyond a straightforward single-span roof — multiple valleys, unusually large catchment areas, or cyclonic wind regions — a licensed plumber should confirm sizing against AS/NZS 3500.3, which specifies drainage requirements based on actual roof catchment area and local rainfall intensity, not just gutter length.
Frequently Asked Questions
Only if your veranda roof is flat/straight rather than curved (bullnose). If you want the curved bullnose look, Custom Blue Orb is the correct product — standard Custom Orb isn't manufactured or warranted for curving.
This tool uses a simplified length-based rule of thumb. Real downpipe requirements depend on total roof catchment area and local rainfall intensity under AS/NZS 3500.3, so roofs with steep pitches, multiple valleys, or high-rainfall regions may need more than this estimate suggests. A licensed plumber can confirm exact requirements.
A minimum fall of 1:500 toward the downpipe outlet is the standard recommendation — meaning the gutter drops at least 1mm for every 500mm it runs.
In most Australian states, roof plumbing and guttering work is licensed work. Check your local regulations before starting — DIY installation can also void insurance coverage for any resulting water damage.
Enter the slope length — the actual distance up the roof from eave to ridge (or eave to the next level), the same measurement a contractor takes directly on the roof with a tape. If you only know the horizontal (plan) span and the pitch angle, use the pitch converter above the roof sections to work out the equivalent slope length first.
Standard Custom Orb corrugated roofing needs a minimum 5° pitch to shed water properly without leaking. Below that, Trimdek (rated to 2°) or Klip-Lok (rated to 1°) are the correct products — different profiles with different coverage widths, so this calculator's figures wouldn't apply directly to them.
Sheets can typically be custom-ordered up to 8m long, which covers most residential runs in one piece. If a run genuinely needs two sheets joined end to end, allow a minimum end lap of 150mm for pitches of 5° or more, or 200mm for pitches below 5° — add this to your section's depth measurement to make sure you order enough length.