What Size Ladder to Use for Getting on a Roof

The right ladder size is critical for safety and efficiency when accessing a roof. This guide explains how to choose ladder length based on roof height, pitch, and task, plus placement, ratings, and common scenarios to help Americans make an informed purchase.

Roof Height (Wall)	Typical Ladder Length Needed	Extension Above Roof
1–8 Feet (Shed/Low)	8–12 Foot Step Ladder	2–3 Feet
9–16 Feet (One-Story)	16–20 Foot Extension Ladder	3 Feet
17–24 Feet (One-and-a-Half/Two-Story)	24–28 Foot Extension Ladder	3 Feet
25–36+ Feet (Two-Story Tall)	28–36+ Foot Extension Ladder	3 Feet

How Ladder Length Is Measured And Why It Matters

Ladders are measured by their overall length when closed (step ladders by height and extension ladders by maximum extended length). Using a ladder that is too short forces risky standing positions and increases fall risk. Proper sizing ensures stability and allows the ladder to extend above the roofline for safe transition on and off the roof.

Calculating Ladder Length For Roof Access

Begin by measuring the vertical height from the ground to the roof edge (the wall height). Then account for the recommended extension above the roofline: extension ladders should extend at least three feet above the roof edge to provide a secure handhold when stepping onto the roof.

Practical Formula

Choose Ladder Length = Wall Height + 3 Feet (minimum) + allowance for angle and ground distance. Because extension ladders lean, add extra length to account for the 75.5-degree working angle; this increases the ladder’s required overall length compared to the vertical height.

Roof Pitch And Its Effect On Ladder Choice

Roof pitch (rise over run) affects how far the ladder base must sit from the wall. Steeper roofs push the base further out, requiring slightly longer ladders. For steep pitches, add 1–2 feet to the ladder length calculation to maintain proper setup angle and clearance.

Examples By Pitch

• Low Pitch (≤4/12): Standard ladder length calculation applies.
• Medium Pitch (5/12–8/12): Add 1 foot for clearance and angle.
• Steep Pitch (9/12+): Add 1–2 feet and consider ladder stabilizers to keep contact points secure.

Recommended Ladder Types For Roof Work

Different tasks require different ladder types. Extension ladders are the primary choice for roof access due to adjustable length and ability to reach high eaves. Step ladders, platform ladders, and articulating multiposition ladders may serve for low roofs or working on gutters and soffits.

• Extension Ladders: Best for most roof heights; available from 16 to 40 feet.
• Step Ladders: Useful for low roofs and single-story tasks; do not stand on the top rung.
• Multi-Position/Articulating Ladders: Versatile for uneven terrain and attic-to-roof transitions.

Proper Ladder Angle, Placement, And Support

For extension ladders, the recommended setup is a 4:1 ratio—place the base one foot out for every four feet of ladder height to the support point. At this angle the ladder is stable and minimizes slip risk. Use level ground, a ladder leveler on slopes, or secure-foot accessories where necessary.

Top Support And Overlap

Ensure sufficient overlap for extension ladders: for each foot of ladder length above 36 feet, follow manufacturer recommendations for minimum fly overlap to maintain strength and stability.

Required Ladder Extension Above Roof And Why It’s Needed

Ladders must extend above the roofline to allow a secure hand transition. OSHA and safety experts recommend a minimum of 3 feet of ladder above the roof edge. Less extension forces awkward transitions and increases fall risk when climbing on or off the ladder.

Weight Capacity And Duty Ratings

Ladders are rated by duty type indicating maximum load, including the user and tools. Common ratings include Type IAA (375 lb), Type IA (300 lb), Type I (250 lb), Type II (225 lb), and Type III (200 lb). Select a ladder with a duty rating that exceeds the combined weight of user and gear to ensure safety and durability.

Choosing Ladder Material: Aluminum, Fiberglass, Or Wood

Material affects weight, conductivity, and durability. Aluminum ladders are lightweight and rust-resistant but conduct electricity, so they are not safe near live wires. Fiberglass is heavier but non-conductive and preferred for electrical work. Wood is less common but still used for specific scenarios.

Accessories And Safety Enhancements

Accessories improve ladder performance and safety. Top stabilizers, ladder levelers, non-slip feet, and ladder standoffs for gutter work reduce risk and extend reach.Consider a tie-off strap or ladder anchor to secure the ladder to the roof or fascia for high-wind conditions.

• Stabilizers/Standoffs: Keep ladder head clear of gutters and improve side-to-side stability.
• Ladder Levelers: Allow safe placement on uneven ground.
• Non-Slip Feet and Safety Shoes: Improve ground grip.

Typical Ladder Recommendations By Building Type

Building	Wall Height	Recommended Ladder
Shed/Small Garage	1–8 ft	8–12 ft Step Ladder or 12–16 ft Extension Ladder
One-Story House	9–12 ft	16–20 ft Extension Ladder (extend 3 ft)
One-And-A-Half Story	13–17 ft	20–24 ft Extension Ladder
Two-Story House	18–24 ft	24–32 ft Extension Ladder

Common Mistakes And How To Avoid Them

Many accidents occur from incorrect ladder length, poor angle, unsecured base, and using metal ladders near power lines. Avoid standing above the third rung from the top, overreaching, and using ladders on unstable surfaces.Always inspect the ladder before use for damage and loose components.

Inspection, Maintenance, And Storage

Regular inspection prevents failures. Look for bent rails, cracked rungs, loose bolts, and worn feet. Clean ladders after use, store them horizontally on racks, and replace damaged components immediately.Follow manufacturer maintenance guidance for hinges and pulleys on extension models.

Buying Tips And Where To Shop

Test ladder feel, check weight ratings and warranty, and buy from reputable brands with clear specifications. Local home centers, specialized ladder manufacturers, and online retailers offer good selections—compare features like rung spacing, material, and included accessories.Consider renting an extra-long ladder for occasional high-work rather than buying a rarely used oversized ladder.

When To Hire A Professional Instead Of Using A Ladder

Certain tasks are safer for professionals, including work at extreme heights, on very steep roofs, or when electrical hazards are present. If the job requires heavy equipment, complicated framing, or the homeowner feels unsure, hire a licensed roofer or contractor.Insurance and specialized gear reduce risk for complex projects.

Quick Safety Checklist Before Climbing

• Confirm ladder length and duty rating exceed task requirements.
• Inspect ladder for damage, clean rungs and feet.
• Position base at the 4:1 angle and ensure the top extends 3 feet past the roofline.
• Secure ladder at the top or use stabilizers and a spotter when possible.
• Wear non-slip footwear and remove tools from pockets; use a tool belt or hoist to raise equipment.

Summary Of Key Points

Select a ladder length that exceeds the vertical wall height by at least three feet, adjust for roof pitch, and choose the proper duty rating and material for the job.Proper placement, accessories, and inspection dramatically reduce fall risk and improve task efficiency. For tall or complex jobs, consider renting larger equipment or hiring a professional.