Infographic
Commercial roofing supply is rarely a single pallet of roof sheets. On a warehouse, school hall or industrial unit around Melbourne, the "roof package" spans insulation blankets, sarking, safety mesh, fasteners, roof sheets, ridge and barge flashings, sealants, roof vents and often a full rainwater system. Ordering these as disconnected one-offs is how projects end up with crews standing down while someone chases a missed flashing run or the wrong screw length.
PREZO structures pack lots the way roofers actually install — so your bill of quantities maps to deliveries that match the program.
Start with the roof build-up, not the sheet list
Before quantities, confirm the assembly from inside to outside:
- Ceiling or open structure (affects insulation location)
- Under-purlin services and mesh requirements
- Foil-faced blanket or batt-only insulation
- Reflective sarking or combined product
- Roof sheet profile, gauge and coating (COLORBOND® vs ZINCALUME®)
- Flashings, cappings, gutters and downpipes
Each layer has different units — rolls, linear metres, sheets and boxes of fasteners. A pack lot quote should show all of them against the same roof area so you can sanity-check coverage.
Pack lot 1 — Insulation and membrane
For a typical metal deck commercial roof:
- Roofing blanket — roll width usually 1200mm; calculate from purlin layout and end laps. Allow for 5–10% waste on complex roofs.
- Sarking — if separate from blanket, roll length and lap overlap per manufacturer (commonly 150mm minimum).
- Foil tapes — one roll rarely covers a large commercial job; specify double-sided and single-sided tapes for laps and penetrations.
- Safety mesh — if required under blanket; confirm span ratings.
Reference the energy report or specification for target R-value. PREZO ThermaRoof and CSR Bradford lines each have thickness-to-R-value tables — match the modelled product, not an approximate thickness.
Pack lot 2 — Roof sheets and flashings
Roof sheet quantity is driven by cover width, not sheet width. Trimdek®, Klip-Lok® and custom orb each have different effective covers. Add:
- Ridge capping and ridge vent lengths
- Barge and gable flashings
- Apron and step flashings at walls
- Valley and box gutter items if applicable
- Z-nuts, closures and foam fillers for profile ends
Flashings are where pack lots often fail. Measure perimeter, penetrations and plant platforms on plan — then add a sensible bend wastage. Colour match all formed items to the sheet batch to avoid visible variation.
Pack lot 3 — Fasteners and accessories
Fastener selection depends on sheet profile, purlin material, thickness and pull-out requirements. A commercial pack lot should separate:
- Roof sheet screws (with correct drill point and washer)
- Stitch screws for flashings
- Rivets and brackets where specified
- Sealants compatible with COLORBOND® (avoid incompatible silicones)
See our guide on COLORBOND fastener selection for profile-specific notes. Wrong screws strip out or void warranties — they are not interchangeable commodities.
Pack lot 4 — Ventilation and rainwater
Warehouse programs often treat these late, but they belong in the initial pack lot:
- Ventilation — ridge vents, turbine vents or mechanical penetrations; size for condensation control, not just code minimums.
- Rainwater — gutter capacity, downpipe sizing, brackets and sumps. Commercial facades may need larger box gutters — calculate from catchment and rainfall intensity for the site.
PREZO supplies roofing insulation, sarking and roof ventilation on one account — use that to lock quantities and specifications together.
Waste factors and site realities
Experienced estimators apply:
- 3–5% sheet waste on simple rectangles
- 8–12% on roofs with multiple penetrations, cranked sheets and odd bays
- Roll product waste higher when bays do not divide evenly into roll length
Confirm whether the quote is supply only or includes delivery placement. Large sites may need hi-ab placement points identified before the truck books.
Staged delivery aligned to program
On multi-stage projects, split pack lots by building or by install sequence:
1. Mesh, blankets, sarking — delivered before internal crane or roof install 2. Sheets and flashings — timed to weather windows 3. Gutters and downpipes — often after scaffold strike or facade completion
PREZO runs staged delivery for large Victorian programs — see staged delivery for roofing programs for how we structure drops against your crane schedule.
What to send for an accurate quote
The fastest commercial quotes come with:
- Roof plans with areas, pitches and profiles noted
- Energy report or insulation specification
- BAL level if applicable
- Colour selections and sheet gauge
- Preferred delivery dates and site access notes
A complete pack lot is not about ordering more — it is about ordering once, correctly, with the roof crew able to fix the whole assembly without emergency runs to the trade counter. That is how PREZO approaches commercial supply in Melbourne.
