Roof Access Systems: What AS 1657 Actually Requires for Ladders, Hatches, and Walkways

Safe roof access is not an afterthought. Before any anchor point, static line, or edge protection system can be used effectively, workers need a compliant means of getting onto and moving across the roof. Yet access systems are frequently the weakest link in a building's height safety programme, either because they were never designed to a standard or because the original installation no longer meets current requirements.

This post covers what AS 1657 requires for fixed ladders, platforms, walkways, and stairways, when a simple access hatch is legally sufficient, and what different access configurations cost to install on a commercial or industrial building.

What AS 1657 Covers

AS 1657 (Fixed platforms, walkways, stairways and ladders: Design, construction and installation) is the primary Australian standard governing permanent means of access to elevated areas, including rooftops. It applies to any fixed access structure installed on a building, whether that is a vertical ladder bolted to a parapet wall, a ship's stair rising through a plant room, or a walkway spanning a membrane roof.

The standard sets out dimensional requirements, load ratings, handrail specifications, slip resistance, and the conditions under which each access type is appropriate. It does not cover portable ladders, which fall under AS/NZS 1892, or personal fall protection equipment, which is governed by AS/NZS 1891.1-4:2025.

For building designers and facilities managers, the practical implication is this: if a worker needs to access a roof on a regular basis, a compliant fixed access system is required. "Regular basis" in WHS terms generally means more than incidentally, and regulators have taken a broad view of that definition.

Fixed Ladders: When They Are Acceptable and What They Must Include

A fixed vertical ladder is the lowest-cost access solution and is appropriate in specific circumstances. AS 1657 permits vertical ladders where the access frequency is low, where space constraints make a stairway impractical, and where the vertical rise does not exceed certain thresholds without rest platforms or fall arrest provisions.

Key dimensional requirements under AS 1657 include:

• Rung spacing: : 225 mm to 300 mm centre-to-centre
• Rung width: : minimum 300 mm clear width between stringers
• Clearance behind rungs: : minimum 150 mm from the centreline of the rung to any obstruction
• Clearance in front of rungs: : minimum 750 mm from the rung face to any obstruction on the climbing side
• Inclination: : vertical ladders must be between 75 and 90 degrees

For ladders exceeding 6 metres in height, AS 1657 requires either a ladder cage (a series of hoops forming a safety cage around the climber) or a ladder safety device, which is a fixed rail or track that accepts a fall arrest device attached to the worker's harness. Ladder cages were the traditional solution, but they are now understood to provide limited actual fall protection and are increasingly being replaced with fixed rail systems on new installations.

At the top of the ladder, the standard requires a secure landing or platform, with handrails or a grab rail at the transition point. A common non-compliance on older buildings is a ladder that terminates at a parapet with no grab rail, leaving the worker to make an unsupported transfer from the ladder to the roof surface.

Access Hatches: When They Are Sufficient

An access hatch, combined with a fixed ladder below it, is a compliant and cost-effective solution for rooftops accessed infrequently and by a small number of workers at a time. "Infrequently" in practice means maintenance visits several times per year rather than daily or weekly access.

For the hatch itself, AS 1657 requires that the opening be large enough to allow a worker wearing a harness and carrying tools to pass through without difficulty. The minimum clear opening dimension is 600 mm x 600 mm, though 750 mm x 750 mm is the practical standard for workers in PPE. Hatches must be openable from both sides, must not require the worker to reach across or over the opening to operate the latch, and must stay open without being held.

The ladder-to-hatch transition is where many installations fail. The top rung of the ladder must be level with or above the finished floor or roof surface at the hatch, and there must be a secure handhold at the point of egress. A grab rail mounted to the hatch frame or the adjacent structure satisfies this requirement.

If the roof is accessed by multiple trades simultaneously, or if the access route involves carrying equipment that makes ladder climbing hazardous, a hatch and ladder combination is generally not sufficient. At that point, a stairway or ship's ladder becomes the appropriate solution.

Stairways and Ship's Ladders: The Step Up from Vertical Ladders

AS 1657 distinguishes between stairways (inclination between 20 and 45 degrees) and alternating tread devices and ship's ladders (inclination between 45 and 75 degrees). Ship's ladders are a practical middle ground for plant rooms and roof access structures where a full stairway cannot be accommodated but a vertical ladder is unsuitable due to access frequency or load-carrying requirements.

For stairways, the standard specifies:

• Tread depth: : minimum 215 mm going (horizontal measurement)
• Riser height: : 150 mm to 225 mm
• Width: : minimum 550 mm clear width for industrial stairways, 1,000 mm for public access
• Handrails: : required on both sides where the stair width exceeds 1,000 mm; on at least one side for narrower stairs
• Slip resistance: : treads must meet a minimum slip resistance rating appropriate to the exposure conditions

For rooftop access structures, a ship's ladder with handrails on both sides is often the most practical solution where a full stairway cannot be installed due to structural or spatial constraints. The key advantage over a vertical ladder is that workers can descend facing forward and can carry equipment more safely.

Walkways: When a Permanent Path Is Required

A walkway system becomes necessary when the roof surface itself is not a safe walking surface, when workers need to traverse the roof to reach plant, anchors, or other equipment, or when the access route crosses fragile materials such as fibreglass sheeting, corrugated metal with unsupported spans, or membrane roofing over insulation.

AS 1657 sets minimum walkway widths at 600 mm clear, with 900 mm preferred where workers carry equipment. Handrails are required where the walkway is elevated more than 300 mm above the adjacent surface or where a fall from the walkway edge would result in injury.

On industrial buildings with corrugated metal roofing, a fixed walkway along the ridge or across the roof plane is often the only compliant means of access to rooftop plant. Without it, every maintenance visit involves workers walking on a fragile surface, which is both a WHS breach and a significant liability.

Walkway systems on commercial flat roofs are less common but are required where membrane or ballasted roofing would be damaged by foot traffic, or where the access path crosses a rooftop with multiple levels and changes in height.

Cost Considerations for Different Access Configurations

Access system costs vary considerably depending on the configuration, the height of the structure, and the materials specified. The following figures are indicative for Sydney commercial and industrial buildings as of mid-2026.

Fixed vertical ladder with cage or rail system: $2,500 to $6,000 installed, depending on height and whether a fixed rail or cage is specified. Fixed rail systems cost more upfront but are the preferred solution for new installations.

Access hatch (aluminium, single-skin): $800 to $2,500 supply and install, depending on size and whether a curb is required. Insulated or double-skin hatches for climate-controlled buildings cost more.

Ship's ladder with handrails: $4,000 to $9,000 installed, depending on height and structural connection requirements.

Full stairway to roof level: $12,000 to $35,000 or more, depending on height, materials, and whether the structure requires engineering certification.

Rooftop walkway system (per linear metre): $350 to $700 per metre installed for a steel grating walkway with handrails on corrugated metal roofing. Aluminium systems cost more but require less maintenance.

These costs should be considered alongside the cost of the fall protection system itself. An anchor point or static line system installed on a roof without compliant access is a system that cannot be safely used, which means the investment in fall protection is effectively stranded until the access issue is resolved.

The Design Sequence That Avoids Expensive Retrofits

The most common and costly mistake in rooftop height safety is designing the fall protection system without first resolving the access system. Building designers who specify anchor points on a new building without also specifying a compliant access route are leaving the compliance gap for the facilities manager to resolve later, usually at a higher cost.

The correct sequence is:

• Identify all rooftop areas requiring maintenance access
• Determine access frequency and number of simultaneous users
• Select the appropriate access type (hatch and ladder, ship's ladder, stairway) based on AS 1657 criteria
• Design the fall protection system for the roof areas accessed
• Ensure the access system and fall protection system are compatible (for example, that a worker exiting a hatch can immediately connect to an anchor or static line)

For existing buildings, a height safety audit should assess both the access system and the fall protection system together. Auditing anchors without auditing access produces an incomplete picture of the building's compliance status.

Practical Compliance for Facilities Managers

If you manage a building where roof access exists but has never been formally assessed against AS 1657, the starting point is a documented inspection of the existing access system. Check rung spacing, clearances, handrail heights, and the condition of any fixed ladder or walkway components. Note any deficiencies and assess whether they can be remediated or whether a replacement system is required.

For buildings where rooftop plant is being added or replaced, the access system should be reviewed as part of the project scope. Adding an air conditioning unit to a roof that is accessed by a non-compliant ladder is an opportunity to bring the access system up to standard at the same time, rather than treating it as a separate project.

Height Safety Sydney carries out access system assessments as part of its height safety audits, covering both the access route and the fall protection system. If you are unsure whether your current roof access arrangement meets AS 1657 requirements, visit [https://sydney.height-safety.au](https://sydney.height-safety.au) to arrange an assessment.