Structural Requirements for Pergolas and Carports

What This Requirement Covers

This requirement outlines the structural and related construction provisions that apply to pergolas and carports in Australia under the National Construction Code (NCC) / Building Code of Australia (BCA) and associated Australian Standards. It explains when a structure is treated as an appurtenant, unroofed pergola or a roofed carport, what loads and materials must be considered, and the performance and fire-resisting obligations that affect design, construction, and siting. The provisions exist to ensure safety (structural stability, wind and snow loads where applicable), weatherproofing, and appropriate fire separation between detached or attached outbuildings and primary buildings.

These rules apply to designers, builders, certifiers and homeowners involved in constructing or modifying pergolas and carports. They are relevant to Class 1 (single dwelling) and Class 10 (non-habitable structures) residential work, and to larger/attached covered structures where aspects of NCC Volume One or Volume Two may apply depending on classification and connection to the main building.

Key Requirements

1. Definitions and classification
2. Pergola - commonly treated as an unroofed or partially roofed, open structure associated with a Class 1 building; may be treated as an allowable encroachment when unroofed (see ABCB Housing Provisions Standard 2022, Figure 9.2.9c).
3. Carport - a roofed structure for vehicle shelter; when associated with a Class 1 building it is often treated under the ABCB Housing Provisions (see Figures 9.2.8a/9.2.8b and associated text).

Structural design standards and references

1. Structural design must comply with NCC structural provisions: Section B Structure (NCC Volume One) and the relevant parts of NCC Volume Two for housing work. For timber construction use AS 1684 (Design of timber-framed structures) and AS 1720.1 for design of timber structures (NCC references: Section B Structure, and lists of acceptable materials in NCC Volume One). For steel members use AS 4100 (Steel structures) where applicable. Piling must follow AS 2159 when required. (See NCC Volume One, Section B Structure and referenced standards.)

Loadings and member sizing

1. Design for relevant actions per NCC and AS/NZS 1170 series (wind actions, imposed loads): wind loading must be calculated to the site-specific wind classification and region as described in AS/NZS 1170.2.
2. Typical practical minimums (subject to structural design):
3. Post sizes: Common timber posts for small pergolas/carports are typically 90 x 90 mm or 100 x 100 mm treated structural timber; larger spans or loads require structural design in accordance with AS 1684 and AS 1720.1.
4. Beam sizes and spans: Beam and rafter sizing depends on span and imposed loads - design per AS 1684 tables or engineered design; do not assume arbitrary sizes without calculation.
5. Foundations: Footing sizing must resist uplift and overturning from wind - typical pad footings for timber posts are often 300-450 mm diameter x 400-600 mm deep (or designed per engineer) for domestic carports/pergolas; if using bolted base plates to slab confirm anchorage per AS 4100 or AS 1684 and the slab design.

Weatherproofing and roof coverings

1. Roof coverings for carports must meet NCC roof covering provisions where applicable (NCC Volume One, F3D2): acceptable roof materials include metal sheet roofing complying with AS 1562.1, plastic sheet roofing in accordance with AS 1562.3, and sarking complying with AS 4200.1/4200.2.
2. Unroofed pergolas may be treated differently in the Housing Provisions - see Figure 9.2.9c for allowable encroachments and boundary setbacks when unroofed.

Fire-resisting and separation requirements

1. Carports and pergolas adjacent to boundaries and to Class 1 buildings must comply with the ABCB Housing Provisions Standard 2022 fire-resisting rules for appurtenant structures (see Clauses and Figures 9.2.8 and 9.2.9). Key points:
2. Where a carport has a common roof with the Class 1 building and no ceiling, openings between the top of the Class 1 wall and underside of the roof covering must be infilled with non-combustible material or be clad with non-combustible material on the carport side (ABCB Housing Provisions Standard 2022, Figure 9.2.8 and associated text).
3. An unroofed pergola may be permitted to encroach within 900 mm of a boundary in certain situations (ABCB Housing Provisions Standard 2022, Figure 9.2.9c) - check the Housing Provisions for full conditions.

Relevant clauses and standards (examples)

1. NCC Volume One - Section B Structure (refer to specific structural clauses and referenced standards lists).
2. NCC Volume One - F3D2 Roof coverings (see roofing material requirements).
3. ABCB Housing Provisions Standard 2022 - Clauses and Figures 9.2.8, 9.2.9 and associated explanatory information (fire-resisting requirements for carports and allowable encroachments for pergolas).
4. AS 1684 series - Timber framing design and span tables (timber pergolas/carports).
5. AS 4100 - Steel structures (where steel members or connections used).
6. AS/NZS 1170.2 - Wind actions (site wind classification and design loads).
7. AS 2159 - Piling (if piles used).

Residential vs Commercial

1. Residential (Class 1 and Class 10a): Most pergolas and small carports associated with single dwellings are treated under NCC Volume Two (Housing Provisions) and the ABCB Housing Provisions Standard 2022. Requirements focus on:
2. Fire separation and allowable encroachments (e.g., unroofed pergola encroachment within 900 mm in certain cases - ABCB Housing Provisions Standard 2022, Figure 9.2.9c).
3. Simpler structural design paths using AS 1684 span tables for timber framing where applicable.
4. Where carports share a roof or are close to boundaries, non-combustible infill or cladding and fire-resisting walls up to underside of roof cladding may be required (Figures 9.2.8a/9.2.8b and explanatory text).
5. Commercial or attached structures (Class 2 - 9): Covered structures that form part of, or are attached to, Class 2-9 buildings typically fall under NCC Volume One structural and fire provisions, and are treated with greater emphasis on certified structural design, FRLs and performance. Key differences:
6. Structural design must satisfy Volume One B Structure clauses, with FRLs and fire separation requirements where the carport or pergola affects fire compartments or egress.
7. Greater requirement for engineered design (AS 4100 for steel, certified timber designs per AS 1720.1/AS 1684) and more stringent material choices for fire exposure.

Exceptions and Exemptions

1. Small unroofed pergolas may be treated as allowable encroachments close to boundaries under the ABCB Housing Provisions (refer to Figure 9.2.9c and clause text) when they meet the definition of unroofed and other conditions.
2. A carport may be exempted from some requirements if it is open, does not provide direct structural support to the house, and satisfies the Housing Provisions conditions (see ABCB Housing Provisions Standard 2022 Figure 9.2.8 and accompanying clauses).
3. Where work is entirely Class 10a (non-habitable) and detached, NCC Volume Two or the Housing Provisions may provide simplified requirements; however, if the carport/pergola forms part of the primary building or affects fire separation, Volume One provisions will apply.
4. State and territory schedules may modify or add requirements - these can create additional exemptions or tighter rules.

State and Territory Variations

1. The NCC is national but each jurisdiction can alter provisions via state schedules in NCC Volume One. The ABCB Housing Provisions Standard 2022 includes state-specific inserts and examples (see the state inserts in the Housing Provisions):
2. Queensland, New South Wales, Victoria, South Australia, Western Australia, Tasmania, ACT and Northern Territory may include modifications to fire-separation or encroachment dimensions, or additional construction limitations.
3. Example: South Australia includes specific wording and figures for fire-resisting requirements for carports or verandahs with or without ceilings (ABCB Housing Provisions Standard 2022, SA Figures 9.2.8a/9.2.8b and supporting text).
4. Always check the relevant state schedule in NCC Volume One and the state inserts in the Housing Provisions for local amendments before finalising design or construction.

Practical Compliance Tips

1. Check classification early - confirm whether the structure is treated as Class 10a/1 or part of a Class 2-9 building; this determines whether NCC Volume Two (Housing Provisions) or NCC Volume One applies.
2. Use the correct standard for material and load design - timber pergolas use AS 1684 and AS 1720.1, steel elements use AS 4100, and wind loads must follow AS/NZS 1170.2. Quote the clause or table used in design documentation.
3. Don’t assume post or footing sizes - use AS 1684 span/footing tables or an engineer’s design. Typical post sizes (90 x 90 mm or 100 x 100 mm) are only a guide and may be insufficient near boundaries or in high-wind areas.
4. For carports sharing a roof with a dwelling, ensure any openings between the wall and roof underside are infilled or clad with non-combustible material as required by the Housing Provisions (see Figures 9.2.8a/9.2.8b).
5. If locating a pergola near a boundary, verify allowable encroachment limits - unroofed pergolas can have different rules (e.g., 900 mm encroachment reference in ABCB Housing Provisions Figure 9.2.9c). Check the exact clause and figure for full conditions.
6. Document compliance: include the specific NCC clause references and Australian Standard citations on drawings and specifications (for example: “Designed to AS 1684 and AS/NZS 1170.2; fire separation per ABCB Housing Provisions Figure 9.2.8”).
7. Where any doubt exists (complex spans, high wind region, boundary/fire issues), engage a structural engineer or registered certifier and check the relevant state schedule in NCC Volume One and the ABCB Housing Provisions Standard 2022.

References cited inline in the text are from the National Construction Code (NCC 2022 Volume One and Housing Provisions) and referenced Australian Standards including AS 1684, AS 1720.1, AS 4100, AS/NZS 1170.2, AS 1562.1/1562.3, AS 4200.1/4200.2, and AS 2159. For specific clause and figure locations see NCC Volume One (Section B Structure; F3D2) and ABCB Housing Provisions Standard 2022 (Figures and Clauses 9.2.8 and 9.2.9).