Repair Systems — 03 — Facade & External Envelope
Duplex coated steel flat bar lintel
Technical product reference for duplex coated steel flat bar lintels for masonry facade remediation on Australian Class 2 strata buildings. Covers HDG plus PU paint flat bar lintels for shallow rebate inland masonry openings. Structural engineer confirmation of span and deflection capacity is mandatory before specifying.
What is a duplex coated steel flat bar lintel?
A duplex coated steel flat bar lintel is a hot-dip galvanised (HDG) flat bar steel section with a paint overcoat (typically polyurethane or epoxy) applied over the zinc coating. The duplex system provides 40–50 year service life in inland C2/C3 environments. Flat bar lintels are used specifically for shallow rebate masonry openings where the structural depth within the reveal cannot accommodate an equal angle section, and are typically restricted to spans under 2 m due to the lower section modulus of the flat bar profile.
Product Reference
2 supplier systems — duplex coated steel flat bar lintels — scroll to view all
InfraBuild — Duplex coated steel flat bar lintel — HDG + PU paint — shallow rebate
Duplex coated steel flat bar lintel — HDG + PU paint — shallow rebate — inland
System Description
InfraBuild supplies hot-dip galvanised flat bar sections finished with a polyurethane (PU) paint overcoat to form a duplex coating system for shallow rebate masonry lintel applications. Flat bar lintels are used where the available structural depth within the masonry opening cannot accommodate an equal angle section — typically in shallow rebate openings or window reveals where the angle leg would project below the soffit line. Flat bar has a significantly lower section modulus than equal angle of the same nominal height — the structural engineer must confirm the span is within the bending and deflection limits per AS 4100 before specifying. Spans are typically restricted to under 2 m. The AS/NZS 4680 compliant HDG plus PU paint duplex system provides 40–50 year inland service life. Not suitable for coastal or C4/C5 environments.
Technical Properties
- Minimum profile depth — fits within shallow rebate masonry openings where an equal angle section cannot be accommodated
- HDG + PU paint duplex system — zinc coating to AS/NZS 4680 plus polyurethane paint overcoat for extended inland service life
- 40–50 year estimated inland service life in C2/C3 environments when the PU overcoat is maintained
Limitations
- Restricted to short spans — flat bar has significantly lower section modulus than equal angle of the same height; engineer must confirm span is within bending and deflection limits
- Structural engineer must design and certify the lintel section, span and bearing before installation — do not assume a standard flat bar size is adequate
- Not suitable for coastal, marine or C4/C5 corrosivity environments — specify grade 316L stainless steel flat bar for coastal applications
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
State-based masonry lintel fabricators — cut-to-length duplex flat bar lintels
Duplex coated flat bar lintel — cut to length — local fabrication — engineer's drawings
System Description
State-based masonry lintel fabricators supply cut-to-length duplex coated flat bar lintels fabricated to the structural engineer's drawings for shallow rebate masonry opening applications. This option is used when the required flat bar dimensions are not available as standard merchant stock, or when the project specification requires a precise duplex coating system applied to confirmed dimensions. The fabricator hot-dip galvanises the cut flat bar sections and applies a paint overcoat per the specification. Request a fabrication and coating certificate confirming AS/NZS 4680 compliance before accepting delivery. Confirm the fabricator can accommodate the required flat bar dimensions and duplex coating specification. Not suitable for coastal environments — specify stainless for all coastal flat bar lintel applications.
Technical Properties
- Cut to exact dimensions — avoids waste and ensures consistent bearing length at both ends per the engineer's specification
- Fabricated to engineer's drawings — flat bar dimensions, length and bearing requirements per the structural design
- HDG + paint duplex system applied by fabricator — confirm coating specification (PU or epoxy paint) in the purchase order
Limitations
- Structural engineer's drawings must be provided before ordering — do not order cut-to-length flat bars without a confirmed structural design
- Request fabrication and coating certificate confirming AS/NZS 4680 compliance before accepting delivery
- Not suitable for coastal or marine environments — site corrosivity must be confirmed as C2/C3 inland before specifying duplex flat bar
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of duplex coated steel flat bar lintel systems. Confirm all selections against the structural engineer's design before ordering.
| Supplier | Product | Coating | Sections | Service life | Distribution | Key feature | Primary use |
|---|---|---|---|---|---|---|---|
| InfraBuild | Duplex flat bar lintel | HDG + PU paint | Standard flat bar stock | 40–50 yr inland C2/C3 | National — steel merchant | AS/NZS 4680 certified HDG | Shallow rebate — short spans <2 m |
| State fabricators | Cut-to-length duplex flat bar | HDG + paint — per spec | Engineer-specified | 40–50 yr inland C2/C3 | State-based — local fabrication | Exact dimensions — no waste | Non-standard shallow rebate openings |
Do not confuse duplex flat bar lintel with:
- Duplex angle lintel — equal angle has significantly higher section modulus than flat bar of the same nominal height; angle lintel should be preferred where the opening geometry permits and spans exceed 2 m
- Duplex channel lintel — PFC channel has much higher section modulus than flat bar; for wide openings or heavily loaded masonry where flat bar and angle capacity is insufficient
- Stainless steel flat bar lintel — grade 316L stainless for coastal and marine environments; required wherever the site is within 1 km of the coast or classified C4/C5
Disclaimer
This page provides general technical information only. Duplex coated flat bar lintel design, section size, span capacity and bearing length must be confirmed by a structural engineer per AS 4100 and AS 3700 before specifying. Flat bar deflection must be checked against L/500 under full masonry load.