/ Field knowledge · IMC 306.5
A portable ladder is not 306.5 access.
If reaching the unit means climbing higher than 16 feet above grade, IMC 306.5 wants a fixed interior or exterior access. No portable ladders. The route cannot require going over obstructions taller than 30 inches or walking on roofs steeper than 4:12. Group R-3 is exempt. Show the ladder, landings, and a receptacle on the permit set — not only in the specifications.
Educational 2024 International Mechanical Code (IMC) 306.5–306.5.2 from Daily Code Talk, with IBC guards/platforms and NFPA 70. Confirm the adopted edition. Distinct from service space (306.1–306.4). This is not a ladder design.
- Fixed ladder (from the supplied 306.5 content): rails 42 in above roof/hatch/landing; rungs 10–14 in on center; top rung not more than 24 in below the roof/hatch/parapet; toe space 7–12 in; rail spacing at least 16 in; rungs at least 3/4 in diameter, 300 lb. Climbs more than 30 ft: offset sections and landings (at least 18 in and at least ladder width, 100 psf, with guards). Climbing clearance 30 in from rung centerline; 15 in clear each side; bottom landing 30×30; top landing 30 in deep.
- Catwalks: at least 24 in wide with rails meeting service-platform criteria.
- 306.5.1 sloped roofs: 3:12 or steeper with edges more than 30 in above grade — level platform on each serviced side (at least 30 in any direction) with 42 in guards (21-in sphere; IBC loading). Do not require walking on roofs steeper than 4:12.
- 306.5.2: receptacle at or near the equipment per NFPA 70.
On the set: access path, ladder, 30×30 bottom landing, 30-in-deep top landing, catwalk widths, sloped-roof platforms, nearest service receptacle. Attachment points on or referenced from structural. Equipment tags reference the access detail number.
Portable ladder to a 20-foot RTU, no receptacle
Inspection hold and a fall-risk liability. Coordinate ladder type, landings, parapets, and power early — not at TCO.
Source: Daily Code Talk — IMC 306.5 · tool: Roof-access screen · 306.1: service space.
What to send
How high the unit sits above grade, roof slope if known, and whether a fixed ladder / stair and a service receptacle are shown.
If the only way up is a portable ladder
Send the roof height and the unit location. Masterbuild will say whether 306.5 still has no fixed access — or 306.5.2 still has no receptacle.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Confirm the adopted edition. The 16-foot trigger, ladder dimensions, 4:12 slope, and NFPA 70 receptacle are 2024 IMC 306.5 education from Daily Code Talk — not a ladder or structural design. This page is not legal advice.