For most homeowners, a 24-foot extension ladder handles the majority of tasks around a one or two-story house. But the right size depends on what you’re actually trying to reach, because extension ladders lose several feet of usable length once you set them up safely. A 24-foot ladder, for example, only reaches about 23 feet up a wall and lets you work at a maximum height of roughly 17 feet.
Why a Ladder Is Shorter Than Its Label
Extension ladders have two sections that overlap when extended. For ladders up to 36 feet, the sections must overlap by at least 3 feet. For ladders between 36 and 48 feet, the overlap increases to 4 feet. That overlap eats into your total length immediately.
Then there’s the angle. A safely placed ladder leans against a wall rather than standing straight up, which reduces how high it actually reaches. The standard rule is to place the base 1 foot away from the wall for every 4 feet the ladder rises. So a ladder touching a wall 20 feet up should have its base 5 feet out from the wall. That lean is necessary for stability, but it means the top of the ladder sits lower than its full extended length.
If you’re climbing onto a roof, you also need the ladder to extend at least 3 feet above the roofline so you have something to hold onto while stepping on and off. That’s a federal safety standard, and it means even more of the ladder’s length goes toward the transition rather than reaching height.
Ladder Length vs. Actual Reach
Here’s how nominal ladder sizes translate into real-world performance once overlap and angle are factored in:
- 16-foot ladder: reaches 15 feet up a wall, touches at a max height of 9 feet
- 20-foot ladder: reaches 19 feet, touches at 9 to 13 feet
- 24-foot ladder: reaches 23 feet, touches at 13 to 17 feet
- 28-foot ladder: reaches 27 feet, touches at 17 to 21 feet
- 32-foot ladder: reaches 31 feet, touches at 21 to 25 feet
- 36-foot ladder: reaches 34 feet, touches at 25 to 28 feet
- 40-foot ladder: reaches 37 feet, touches at 28 to 31 feet
The “highest point the ladder will touch” is the range that matters most, since it tells you where the ladder actually contacts the building. Your working height will be a few feet below that contact point, because you should never stand on the top three rungs.
Matching Ladder Size to Your House
A single-story home typically has a roofline between 9 and 13 feet. If you only need to clean gutters, paint siding, or access the roof on a one-story house, a 20-foot extension ladder usually works. It gives you enough length to extend 3 feet past the roofline while still leaning at a safe angle.
Two-story homes are where most people land on a 24-foot or 28-foot ladder. A standard two-story house has a roofline around 17 to 20 feet. A 24-foot ladder can reach roofs on the shorter end of that range, while a 28-foot ladder covers taller two-story buildings and still reaches second-floor windows comfortably. Firefighter training guidelines recommend a 24-foot ladder for second-floor access and a 28-foot ladder for reaching the roof of most two-story buildings.
Three-story homes or buildings with unusually high ceilings may require a 32 or 36-foot ladder. These are heavy, harder to maneuver solo, and more expensive. A 35-foot ladder is what fire services use to reach third-floor windows.
How to Calculate Your Exact Need
Measure the height of what you need to reach, then add length for the setup losses. A simple approach:
Start with the height of the surface you want the ladder to contact. If you’re going onto the roof, add 3 feet for the required extension above the roofline. Then add another 3 feet to account for the section overlap. Finally, round up to the next available ladder size, since extension ladders come in 4-foot increments (16, 20, 24, 28, 32, 36, 40).
For example, if your gutter sits at 18 feet: 18 + 3 (above the roofline) + 3 (overlap) = 24 feet minimum. A 24-foot ladder would work, though a 28-foot would give you a more comfortable margin. When in doubt, go one size up. A ladder that’s slightly too long can be partially retracted, but one that’s too short is useless and tempts you into unsafe positions.
Choosing the Right Duty Rating
Extension ladders are rated by how much total weight they can support, and that total includes you, your clothing, and everything you’re carrying. Five duty ratings exist:
- Type III (Light Duty): 200 pounds
- Type II (Medium Duty): 225 pounds
- Type I (Heavy Duty): 250 pounds
- Type IA (Extra Heavy Duty): 300 pounds
- Type IAA (Special Duty): 375 pounds
If you weigh 200 pounds and carry a tool belt, bucket, or power washer nozzle, you’re already over 200 pounds total. A Type II or Type I ladder gives you a realistic safety margin. Type III ladders are the cheapest option, but the weight limit is tight for most adults once tools are factored in.
Fiberglass vs. Aluminum
Aluminum ladders are lighter, which matters a lot when you’re carrying a 28-foot ladder around the yard. They also cost less. For basic homeowner tasks with no electrical hazards nearby, aluminum is practical.
Fiberglass ladders are heavier but don’t conduct electricity. If your work puts you anywhere near power lines, electrical panels, or overhead wiring, fiberglass is the only safe choice. Contact between a metal ladder and a live wire can complete a circuit through your body, causing a fall, cardiac arrest, or both. The weight penalty is worth it if there’s any chance of electrical contact.
Both materials hold up well outdoors, though fiberglass can degrade over years of UV exposure if stored in direct sunlight. Aluminum won’t rust but can corrode in coastal environments. For most homeowners storing a ladder in a garage, either material lasts decades.
Common Mistakes That Lead to Wrong Sizing
The most frequent error is buying a ladder based on its labeled length and assuming that’s how high you can reach. A 24-foot ladder does not let you work at 24 feet. After overlap, angle, and the rule against standing on the top rungs, your actual working height is closer to 17 feet at best.
Another common mistake is buying too short to save money or storage space. A ladder that barely reaches your roofline forces you to set it nearly vertical, which dramatically increases the risk of it tipping backward. Proper angle requires length to spare.
Storage is worth considering before you buy. A 28-foot extension ladder collapses to roughly 14 feet, and a 24-foot ladder to about 12 feet. Make sure you have wall space in a garage or shed. Longer ladders are also significantly heavier: a 28-foot aluminum ladder typically weighs 45 to 55 pounds, while a 28-foot fiberglass ladder can hit 65 to 75 pounds.