Angles shown are roof-plan angles. The suspended ropes remain vertical. Animation illustrates motion only; it does not calculate forces or fall clearance.
For a fixed lateral offset, increasing setback reduces the plan angle. The table retains the handoff’s selected 12 ft horizontal anchor-spread cap; it is not a universal code limit.
| Setback | Max offset / anchor at 15°* | Pair spread at 25°* | Pair spread at 30°* |
|---|
*Capped at 6 ft per anchor and 12 ft per pair. A symmetric 12 ft spread reaches 15° per side at 22.39 ft setback. There is no 44.8 ft maximum setback implied by these equations.
IWCA safe practices discusses a suspension line within 15° of perpendicular to the roof edge, and separately a suspended worker’s plumb line within 15° from the edge contact point. This lab varies the first, a plan angle.
IWCA safe practices · §§9.3.4, 9.4.2 ↗Each employee using RDS must have a separate, independent personal fall arrest system. Suspension and fall-arrest connections are shown as separate paths in this model.
OSHA 1910.27(b)(2)(vi) ↗Before use, the owner provides written information that each RDS anchorage is identified, tested, certified and maintained to support at least 5,000 lb in any direction for each attached employee. This viewer does not evaluate anchorage strength.
OSHA 1910.27(b)(1) ↗OSHA restricts RDS use above 300 ft unless the specified demonstration supports its use. Stabilization is required at the specific work location for descents greater than 130 ft.
OSHA 1910.27(b)(2)(i), (vii) ↗The 6–50 ft setback range, 12 ft horizontal anchor spread, and 25–30° pair-angle guidance came from the handoff. Their applicability requires review. They are not presented here as independently verified ANSI or OSHA mandates.
Each reference plan angle uses the anchor's horizontal offset from the moving drop center and its inner-face setback. The outer-edge centerline angle also includes parapet thickness. Both protected edge paths move with the worker and stay slightly separated for legibility. The 12 ft spread check measures the horizontal distance between the anchors.
OSHA specifies 42 in ±3 in for top rails or equivalent guardrail members, with conditions for systems higher than 45 in. Green in this model means the parapet is in the reference height band only.
OSHA 1910.29(b)(1) ↗Guardrails must meet the applicable strength and construction requirements, including the 200 lb outward or downward force requirement at the top edge. The model does not check wall strength, openings, or the entire fall-protection system.
OSHA 1910.29(b)(2)–(4) ↗Both ropes pass over distinct protected edge paths. Actual rope protectors, redirects, parapet capacity, access and connections must be selected for the building and equipment.
OSHA 1910.27(b)(2)(v) ↗The red roof band illustrates proximity to the edge. OSHA’s low-slope-roof provisions address employee work and fall protection; they do not establish a blanket ban on anchors within this band.
OSHA provides different requirements depending on distance, work frequency and duration. There is no universally safe green roof band, and this lab does not determine the employee’s protected work zone.
OSHA 1910.28(b)(13) ↗This lesson models a straight parapet. Corners, redirects and changes in facade direction need a separate layout review.