Repair Systems — Roofing Defects — Gutter Replacement
Custom box gutter systems — Colorbond and Zincalume
Box gutters are custom-fabricated from Colorbond or Zincalume steel to suit specific building dimensions and drainage requirements, typically on Class 2 multi-unit residential buildings and commercial structures. Unlike profiled gutters, box gutters are site-formed or fabricated off-site by roofing contractors and require careful design for overflow, falls and outlet sizing.
What are box gutter systems?
Box gutters are custom-fabricated from Colorbond or Zincalume steel to suit specific building dimensions and drainage requirements, typically on Class 2 multi-unit residential buildings and commercial structures. Unlike profiled gutters, box gutters are site-formed or fabricated off-site by roofing contractors and require careful design for overflow, falls and outlet sizing.
Product Reference
2 products — Lysaght and Stratco — custom Colorbond and Zincalume box gutter systems
Lysaght CUSTOM BOX Gutter (Colorbond/Zincalume)
Custom-fabricated Colorbond/Zincalume box gutter — site or shop-formed
System Description
Lysaght CUSTOM BOX Gutter is fabricated from BlueScope Colorbond or Zincalume steel sheet to custom width and depth dimensions suited to the specific building and drainage requirements. Box gutters are not profiled (pre-formed) products — they are formed on site by roofing sheet metal workers or fabricated off-site in a sheet metal shop and delivered to site for installation. Lysaght supplies the Colorbond and Zincalume steel sheet from which box gutters are formed — the gutter geometry is determined by the project-specific design, not by a standard profile. Custom box gutters are used on Class 2 multi-unit residential buildings and commercial structures where roof geometry, parapet details, or drainage requirements make external eave gutters unsuitable. Design must include provision for overflow outlets per AS/NZS 3500.3, minimum fall of 1:200, and appropriate seam and lap joint detailing to ensure watertightness. Available in the full range of current Colorbond colours — Zincalume provides additional corrosion resistance for coastal environments. Confirm current Colorbond sheet availability and thickness options with Lysaght or your roofing contractor before specifying.
Technical Properties
- Custom-fabricated from BlueScope Colorbond or Zincalume steel sheet — width and depth determined by project-specific drainage design
- Site-formed or shop-fabricated — roofing sheet metal workers form the gutter from flat sheet to the specified dimensions
- Full range of current Colorbond colours — Zincalume option for coastal and marine environments
Limitations
- Not a profiled off-the-shelf product — box gutter dimensions must be designed by a qualified person and confirmed against AS/NZS 3500.3 before fabrication
- Minimum fall of 1:200 is required — significantly steeper than for profiled eave gutters — confirm whether the existing structure can accommodate this fall in a replacement scenario
- Overflow outlets are mandatory — sizing and location must be designed to prevent ponding water from entering the building in a blocked-outlet scenario
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Stratco Custom Box Gutter
Custom-fabricated Colorbond/Zincalume box gutter — site-formed — Stratco supply
System Description
Stratco supplies Colorbond and Zincalume steel sheet for site-formed custom box gutters, with matching downpipe and outlet fabrication services available through Stratco trade centres. Box gutters fabricated from Stratco-supplied sheet are formed on site by the roofing contractor from stock Colorbond or Zincalume sheet to the project-specific dimensions. Stratco trade centres can supply matching downpipes, outlets, and fabricated components to co-ordinate with the site-formed gutter. Selection of Stratco as the sheet supplier is typically driven by the roofing contractor's existing supply relationship and the availability of matching fittings and downpipe components from the same supplier. All box gutter design must comply with AS/NZS 3500.3 — minimum fall 1:200, overflow outlet provision, and appropriate seam and lap joint detailing. Confirm current sheet availability, thickness options, and Colorbond colour range with your local Stratco trade centre before specifying.
Technical Properties
- Colorbond and Zincalume steel sheet for site-formed custom box gutters — dimensions determined by project-specific drainage design
- Matching downpipe and outlet fabrication services available through Stratco trade centres — co-ordinated material supply
- All current Colorbond colours — practical for colour matching with existing Stratco roofing and fascia products
Limitations
- Not a profiled off-the-shelf product — box gutter dimensions must be designed by a qualified person and confirmed against AS/NZS 3500.3 before fabrication
- Minimum fall of 1:200 is required — confirm whether the existing structure can accommodate this fall in a replacement scenario
- Overflow outlets are mandatory — must be sized and located to prevent building ingress in a blocked-outlet scenario
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of custom box gutter supply options. Both Lysaght and Stratco supply Colorbond/Zincalume sheet for custom box gutter fabrication — selection is typically driven by roofing contractor supplier relationships.
| Brand | Sheet material | Custom sizing | Overflow provisions |
|---|---|---|---|
| Lysaght | BlueScope Colorbond / Zincalume steel sheet | Fully custom — width and depth to design — site or shop-formed | Overflow outlets required per AS/NZS 3500.3 — designed and sized per catchment |
| Stratco | Colorbond / Zincalume steel sheet — full colour range | Fully custom — site-formed — matching downpipe and outlet supply | Overflow outlets required per AS/NZS 3500.3 — designed and sized per catchment |
Brand Equivalence Note
Lysaght ≈ Stratco— both supply Colorbond/Zincalume sheet for custom box gutter fabrication. Selection is typically driven by the roofing contractor's existing supplier relationship and the availability of matching downpipe and outlet components. Box gutter design and fabrication quality is far more critical than supplier selection — confirm seam detailing, fall, and overflow outlet provision with the fabricating contractor before proceeding.
Do not confuse box gutter replacement with:
- Quad (ogee) gutters — profiled external eave gutters — listed on the quad gutter systems page — entirely different product category and application
- Half-round gutters — profiled external eave gutters — listed on the half-round gutter systems page — not appropriate for internal box gutter applications
- Box gutter relining — a separate scope item where a liquid membrane or GRP lining system is applied inside the existing structural box gutter without full replacement — assess lining vs replacement before specifying
- Box gutter waterproofing — where liquid-applied membrane systems are used to waterproof existing box gutters rather than replacing the steel — listed under waterproofing systems
- Overflow scupper replacement — overflow outlets and scuppers are a separate component that must be co-ordinated with any box gutter replacement scope
Disclaimer
This page provides general technical information only. Final product selection and box gutter design must be confirmed against the current manufacturer technical data sheet, project-specific drainage calculations, AS/NZS 3500.3 requirements for minimum fall, overflow outlet sizing and location, structural conditions, NCC requirements, and contractor supply relationships. Box gutter design and detailing is a specialist scope item — do not rely on this reference as a substitute for professional engineering or building consultant advice.