Calculate safe OSHA 4-to-1 ladder setback distance, 75.5° setup pitch, working length, roof access 3-foot extension, and extension ladder size selection.
Height along the wall, eave, or gutter where ladder will rest.
Requires side rails to extend 3 ft (0.9 m) past upper eave.
Exactly 48 inches from the base of the vertical wall.
Placing a ladder base too far from the wall decreases pitch angle below 70°. As a climber ascends toward the middle, bending moment and outward shear force drastically exceed ground friction, causing the bottom feet to kick outward instantly on concrete, grass, or gravel.
Setting a ladder too steep (near 80° to 85°) makes the ladder feel unnervingly vertical. A worker reaching upward shifts their center of gravity behind the top contact rails, causing the ladder to pitch backward away from the building eave.
OSHA citations frequently cite ladders terminating flush with roof gutters. Stepping sideways onto a roof without 3 feet of rigid rail extension above the edge forces workers to crawl awkwardly on hands and knees, triggering disastrous edge balance loss.
A "24-foot" extension ladder does not provide 24 feet of continuous usable rail. ANSI standards mandate a 3-foot section overlap between the fly and base sections. Forgetting this overlap results in purchasing an undersized ladder that fails to reach the roofline safely.
Measure vertical distance from ground to upper contact support point (gutter, wall, or eave).
Divide vertical height by 4 to get exact base setback distance (ensuring a 75.5° pitch).
If accessing a roof or deck landing, add 3 feet (36 inches) of ladder length past the eave.
Choose Type IAA (375 lb), IA (300 lb), or I (250 lb) based on climber plus tool load.
Ensure work reach stays below the 4th rung from the top to prevent overhead tip-over.
Calculates exact setback distance fulfilling OSHA standard 1926.1053(b)(5)(i) for maximum base traction.
Automatically includes the mandatory 36-inch upper rail safety extension for safe roof transitions.
Accounts for ANSI section overlaps (3 to 4 ft) to specify the exact extension ladder model to purchase or rent.
Seamlessly toggles between feet/inches and meters/centimeters with real-time dynamic diagram rendering.
| Duty Classification | ANSI Type | Total Working Load | Mandatory Section Overlap | Primary Recommended Application |
|---|---|---|---|---|
| Special Duty Extra Heavy | Type IAA | 375 lbs (170 kg) | 3 ft (up to 36') / 4 ft (36-48') | Heavy commercial utilities, industrial rigging, fire rescue |
| Extra Heavy Duty Industrial | Type IA | 300 lbs (136 kg) | 3 ft (up to 36') / 4 ft (36-48') | Roofers, exterior general contractors, heavy tool belts |
| Heavy Duty Commercial | Type I | 250 lbs (113 kg) | 3 ft (up to 36') / 4 ft (36-48') | General commercial maintenance, painters, gutter cleaners |
| Medium Duty Commercial | Type II | 225 lbs (102 kg) | 3 ft (up to 36') | Light commercial repairs, exterior window washing |
| Light Duty Household | Type III | 200 lbs (91 kg) | 3 ft (up to 36') | DIY home maintenance, holiday lights, attic access |
