Special Structures
Roof Platforms and Catwalks for Steel Buildings
Definition: Roof platforms and catwalks are steel access structures installed on or within a pre-engineered building to support rooftop equipment and give maintenance staff a safe, guarded walking route to fans, units, crane rails, lighting or services without walking on the roof sheeting.
Key facts
- Keeps foot traffic off roof sheets, protecting the cladding and reducing fall risk.
- Equipment platforms must bear on members designed for the unit weight and vibration.
- Walking surfaces are commonly open grating for drainage and slip resistance.
- Guardrails, toe boards and access ladders are required by occupational safety rules.
- Penetrations through the roof for platform supports need dedicated flashings.
Role in the structure
Platforms carry the weight of mechanical units, maintenance traffic and stored tools on their own framing, which transfers load through posts or brackets to the main frames rather than the roof sheets. Catwalks provide a continuous walking surface with handrails, and their supports deliver load to rafters, purlins designed for it, or crane runway girders.
Why do metal buildings need roof platforms?
Roof-mounted air handling units, exhaust fans, solar inverters and tanks are heavy and need regular servicing. Placing them directly on profiled sheeting can damage the roof and does not provide a stable base. A steel platform spreads the load into the structure and gives technicians a level, guarded working area.
When equipment is planned for the roof, its weight, footprint and location should be supplied at the quotation stage so that rafters and purlins at that position are designed for it.
Catwalks inside and outside the building
External catwalks run across the roof to link access hatches, ladders and equipment. They are raised on posts above the sheeting so that water drains freely underneath.
Internal catwalks are often hung from rafters or run alongside crane runways to give access to crane rails, conductor systems, lighting and high-level services. Their supports and the members they hang from must be designed for the additional load.
Supports and roof penetrations
Platform posts usually pass through the roof sheeting to bear on the frames. Each penetration needs a pre-formed flashing or curb that suits the roof profile and allows for thermal movement.
For standing seam roofs, non-penetrating clamps fixed to the seams can carry light walkways, but the clamp capacity and the roof system limits must be confirmed by the roof designer.
Materials & coatings
- Hot-rolled or cold-formed steel framing for platforms and catwalks
- Hot-dip galvanized steel grating or perforated plank walkways
- Tubular or angle guardrails with toe boards, galvanized or painted
- Roof penetration flashings, curbs or seam clamps compatible with the roof system
Design considerations
- Obtain equipment weights, footprints and operating vibration data from the supplier.
- Design platform supports to bear on primary members or purlins designed for the load.
- Provide guardrails, toe boards and self-closing gates to the applicable safety rules.
- Use slip-resistant, free-draining walking surfaces.
- Allow for drift snow and wind on raised platforms and screens.
- Plan safe access by ladder, stair or hatch to every platform.
Fabrication
- Frames and posts are fabricated with bolted connections for site assembly.
- Grating panels are cut to size, banded and galvanized after fabrication.
- Handrail sections are shop-welded where possible to reduce site work.
- Components are marked to match the platform layout drawing.
Erection
- Install support posts and flashings before the roof sheeting is completed around them.
- Erect platform framing and fix grating with approved clips.
- Fit guardrails and toe boards before allowing access.
- Seal all penetrations and check flashings for watertightness.
Inspection & quality
- Check grating clips, bolts and handrail connections are complete and tight.
- Inspect flashings at roof penetrations for leaks after rain.
- Verify guardrail height and gate operation against the safety requirements.
- Include platforms in the periodic building maintenance inspection.
What to include in your RFQ
- Equipment list with weights, footprints and locations on the roof.
- Required walkway routes, widths and access points.
- Walking surface type and finish: grating, plank or plate.
- Guarding, ladder and gate requirements and the applicable safety rules.
- Roof system type, so supports and flashings can be matched.
3D model & IFC of this component
Rotate the model, isolate the component and download its IFC4 file for your BIM coordination model.
IFC entity: IfcSlab (LANDING) + IfcRailing. Illustrative geometry for coordination and learning. Final member sizes come from the project design.
Frequently Asked Questions
Can I walk on a metal roof without a catwalk?
Occasional access may be possible on some profiles if foot traffic is limited to supported areas, but regular access should be on walkways. They protect the sheeting and reduce slip and fall risk.
Do roof platforms cause leaks?
Any penetration is a potential leak point. Purpose-made flashings or curbs, correct sealing and periodic inspection keep penetrations watertight.
Can a platform be added after the building is complete?
Yes, but the members it bears on must be checked by an engineer for the new loads, and the roof will need new penetrations or clamps.
Engineering content is general guidance. Every World Steel building is designed by qualified engineers to the code and loads of the project.
