How it's calculated
Every estimate is these lines, in this order, on the measured roof. The worked example is a 14 × 9 m hip at 21° so the numbers are concrete. Quantity is how much; basis is the rule that produced it; rate is your price; the status says whether the rule rests on measurement, published data, or an allowance still to be calibrated.
| Line | Quantity | How the quantity is worked out | Rate | Rate source | Cost |
|---|---|---|---|---|---|
| CUSTOM ORB 0.42 sheet assumed | 214.8 lm | 62 sheets by ceil(eave width / 0.762 m effective cover) on rectangular planes at ordered length; raked planes by true area / cover × pairing allowance; plus 10.0% waste (hip). uses: waste_hip, sheet_gutter_allowance_m, sheet_length_rounding_m, pairing_tri, pairing_trap | $15.36 | placeholder Trade estimate: retail $19 to $25/lm (KCS, Metal Roofing Online, 2026); trade typically 15 to 25% under retail | $3299 |
| Timber batten 90×45 assumed | 176.4 lm | 24 rows across all planes: two end spans at 900 mm and internal spans at 1200 mm, times the average plane width (a triangle's top batten is a point), plus 5% for valleys, plane changes and penetrations. uses: batten_extra | $4.20 | placeholder Web figure, Sep 2026 | $741 |
| Anticon blanket (1200 roll, 1050 effective cover) assumed | 162.0 m2 | True area × 1.2/1.05 for the 150 mm foil tab lost on every lap, plus 5%. uses: anticon_effective_cover_m, anticon_roll_width_m, anticon_extra | $9.00 | placeholder Bradford Anticon 60, 18 m² rolls, retail about $8 to $10/m² (2026 listings) | $1458 |
| Roof safety mesh AS/NZS 4389 assumed | 148.5 m2 | True area plus 10% for 150 mm side laps and end ties. uses: mesh_extra | $4.50 | placeholder Web figure, Sep 2026 | $668 |
| Ridge capping assumed | 5.3 lm | Ridge 5.00 m (horizontal, no multiplier) × 1.05 for 100 to 150 mm laps. uses: capping_lap_allowance | $20.27 | placeholder Metal Roofing Online, Sep 2026 | $106 |
| Hip capping assumed | 27.7 lm | Hip 26.38 m true length using the hip factor √(1 + tan²θ/2), not the plane factor, × 1.05 for laps. uses: capping_lap_allowance | $20.27 | placeholder Metal Roofing Online, Sep 2026 | $561 |
| Penetration flashing / back tray measured | 2.0 ea | One per penetration. Each needs a soaker on the uphill side. | $85.00 | placeholder Web figure, Sep 2026 | $170 |
| Foam infill / rib closure measured | 5.0 lm | Ridge plus barge length. | $3.40 | placeholder Web figure, Sep 2026 | $17 |
| Cyclone assembly (screw + load-spreading washer) assumed | 930.0 ea | Equivalent full-length sheets × (5 per sheet on each of two end supports + 3 on each internal support), plus 15% waste. Cyclonic spans are published WITH cyclone washers. uses: screw_waste | $0.38 | placeholder Class 4 screw plus load-spreading cyclone washer, trade estimate | $353 |
| Batten to rafter screw assumed | 392.0 ea | 2 per crossing at 900 mm rafter centres. uses: rafter_spacing_m, batten_screws_per_crossing | $0.22 | placeholder Bunnings Buildex 12g x 50 class 4, $225 per 1000 (2026); class 3 $145 | $86 |
| Sealant, neutral cure 300 ml assumed | 4.0 ea | One tube per 40 m². Allowance, not a sourced rate. uses: sealant_m2_per_tube_simple | $12.50 | placeholder Web figure, Sep 2026 | $50 |
| Quad gutter 150 (QLD size) measured | 46.0 lm | Eave length, horizontal. | $8.09 | placeholder Metal Roofing Online, Sep 2026 | $372 |
| Downpipe assumed | 5.0 ea | Allowance, not a drainage design: worse of one per 12 m of gutter (4) and plan area / 30 m² catchment (5). Sizing to NCC Part 7.4 / AS 3500.3 for Bundaberg rainfall is the estimator's. uses: gutter_max_m_per_downpipe, dp_catchment_m2_default | $20.82 | placeholder Metal Roofing Online, Sep 2026 | $104 |
| Lay, flash and batten out measured | 135.0 m2 | True area. This is the line the published supply-and-install $/m² rates actually cover. | $34.00 | placeholder AMJ Metal Roofing Brisbane, QLD labour split $40 to $45/m2 supply-and-install, lay share | $4589 |
| Strip the existing roof measured | 126.0 m2 | Plan area. | $18.00 | placeholder Heavy Metal Roofing Rockhampton line item breakdown | $2268 |
| Skip and tip fees assumed | 1.0 ea | uses: skip_count_metal | $520.00 | placeholder Web figure, Sep 2026 | $520 |
| Install gutters and downpipes measured | 46.0 lm | Eave length. | $22.00 | placeholder Web figure, Sep 2026 | $1012 |
| Guardrail edge protection, single storey measured | 46.0 lm | Perimeter guardrail hire for the duration, per lm of eave and barge. Single storey. Allowance; the fall-protection method is assessed on site. | $30.00 | placeholder Guardrail edge protection hire, single storey, about $25 to $40 per lm of perimeter for a one-week job (trade estimate) | $1380 |
Materials
$7987
Labour and site
$9769
Overhead 12%
$2131
Margin 20%
$4971
QBCC insurance
$351
Ex GST
$25209
GST
$2521
Inc GST
$27729
Before the lines: how the roof itself is measured
- Plan area from the building outline (Microsoft satellite-derived footprints), cross-checked against the laser survey's ground area. measured
- Pitch from the Queensland 2016 laser survey: planes fitted to the roof points, main pitch from the dominant planes, low-pitch sections priced separately. Falls back to the street photo, then to a 12 to 28° prior that widens the range. measured
- True area = plan area ÷ cos(pitch). Hips and valleys use √(1 + tan²θ/2), not the plane factor. published geometry
- Form (hip, gable, complex) from the laser plane directions and the aerial read; ridge, hip, eave and barge lengths from the outline rectangle and the form. read from imagery
- Material and storeys from the street photo and aerial read; the customer can confirm. read from imagery
- Wind class by AS 4055 from coast distance and building density, flat ground assumed. Drives batten spacing and fixing density. computed; override per suburb
- Coastal grade: 100 to 200 m from breaking surf, COLORBOND Ultra with compatible coated fasteners as a provisional allowance (BlueScope TB-16; the supplier confirms the fastener specification below 200 m). Inside 100 m the draft stops for a specification. provisional