That's a great question, and a very relevant one for high-end custom homes with ceilings that tall. Here's the breakdown of what you can and can't do with a trestle ladder and its extension, focusing on safety and best practices

Trestle Ladders: Core Functionality
Base Ladder (Trestle Legs)

These are designed to be climbed. They have rungs and are stable when properly set up.

Purpose

Primarily intended as a support for walkboards (planks).

Extension Section: Can you climb it? General Rule: NO, DO NOT CLIMB THE EXTENSION SECTION UNLESS SPECIFICALLY DESIGNED AND RATED FOR CLIMBING. Most trestle ladder extensions are not designed to be climbed directly. Their primary purpose is to provide adjustable height support for the walkboard. Why Not Climb? Lack of Proper Rungs/Steps

The extension might have widely spaced rungs or a system designed only to hold the plank at specific intervals. These are not suitable for safe climbing.

Instability

The extension, on its own, is generally not stable enough to support the weight of a person climbing, especially when extended to a higher position.

Safety Rating

The extension portion of a standard trestle ladder is generally not rated for the weight and stress of climbing. Using it to climb would be misuse of the equipment.

When Might You Climb (With Extreme Caution & Specific Conditions)?

I want to emphasize that this is generally unsafe and not recommended. However, in certain extremely rare situations, and only if the manufacturer explicitly states it's permissible and the ladder is specifically designed for it, you might be able to climb the extension section under very controlled circumstances. This would require: Manufacturer's Approval

The ladder's documentation must state that the extension can be climbed safely and what specific conditions apply.

Specialized Ladder Design

The extension must have proper rungs or steps that meet safety standards for climbing.

Extra Stabilization

Extreme care to assure the entire unit is stable, even beyond normal setup.

Spotter

Absolutely require a spotter at all times.

Limited Weight

Strictly adhere to the weight limit of the entire setup, knowing that stress is higher when climbing.

Perfect Surface

The ground must be completely level and solid.

Proper Angle

The ladder needs to be at the correct angle for climbing if the manufacturer allows climbing the extension.

Best Practices & Safer Alternatives


Use a Separate Ladder

The safest approach is to use a dedicated extension ladder or a step ladder to reach the desired height for tasks outside the area covered by the walkboard.2.

Scaffolding

For very high ceilings, consider renting or purchasing scaffolding. Scaffolding provides a much larger, more stable work platform and is designed for working at height.3.

Aerial Lifts (Scissor Lifts/Boom Lifts)

If the job warrants it, and you have the space, consider renting an aerial lift. This is the safest and most efficient way to work at extreme heights. You'll need training and certification to operate these safely.4.

Trestle Ladder Setup



Stable Base

Always set up the trestle ladder on a level, solid surface.

Proper Spacing

Ensure the trestle legs are properly spread apart according to the manufacturer's instructions.

Walkboard Security

Secure the walkboard to the trestle ladders to prevent it from slipping.

Weight Limits

Never exceed the weight limit of the trestle ladders or the walkboard.5.

Invest in Quality Equipment

Buy high-quality ladders and walkboards that meet or exceed safety standards. Look for certifications like ANSI or OSHA.6.

Training

Make sure you and your crew are properly trained in ladder safety and working at heights.

Recommendation

For the heights you're working with (22'+ ceilings), I strongly recommend focusing on safe alternatives like scaffolding or aerial lifts. Trying to push the limits of a trestle ladder, especially climbing the extension, is a recipe for an accident. While more expensive up front, scaffolding or lifts are a safer long term investment as well as a competitive advantage for being the safety conscious contractor.

Always consult the ladder's manufacturer's documentation and local safety regulations before using any ladder.In summary: Treat the trestle ladder extension primarily as a support for the walkboard, not as a climbing device unless the manufacturer explicitly allows it and you take extreme precautions. Flag for review