Roof Ladders and Roof Stairs: How to choose the right device

With so many different options and applications for roof ladders and roof stairs, it can be difficult to determine what is the best device for each roof application.  Some of the options to access roofs are stairways, roof ladders, fixed ladders or permanent ladders, folding ladders, retractable ladders, ships ladders, and alternating tread stairs. Understanding  roof access code requirements, usability, and safety of each type of device will help you choose the right device. 

Occupied Roofs vs Unoccupied Roofs 

The first step is understanding the different types of roofs. IBC differentiates between occupied and unoccupied roofs. 

Occupied roofs are accessible to building occupants and must be provided by a means of egress. For occupied roofs, think of rooftop lounge areas, swimming pools or other roof assembly areas accessible to the general public. The occupied roof is considered a story within the building like any other enclosed story and the same means of egress requirements apply. 

Unoccupied roofs are accessible only to maintenance or other construction workers. The workers might need to access the roof to service the roof itself or other mechanical equipment located on the roof. 

Roof Stair and Roof Ladder Codes by Application

The next step is understanding the different roof applications. Common applications for roof access includes:

  • Egress from or to occupied roofs
  • Access to unoccupied roofs
  • Exterior access to rooftop equipment or roof elevation changes

Egress to occupied roofs must be through a stairway which meets all the requirements of IBC stairway design.  Additionally, the stairway to a roof must be through a penthouse complying with IBC section 1510.2. With these requirements, stairway access to occupied roofs will typically be an extension of the exit stairways up to the roof.

For unoccupied roofs, under the exception to IBC 1011.12, access to the roof from the top story is permitted to be by an alternating tread device, a ships ladder, or a permanent ladder.  Also, the exception to IBC 1011.12.2 allows access to unoccupied roofs to be a roof hatch or trap door.  So for unoccupied roofs, a ladder or alternating tread stair extending through a roof hatch is the most common method of accessing the roof. 

roof hatch stair

For exterior access to roof equipment or changes in roof elevation, only maintenance or other construction workers will be allowed access to these areas. Access devices for these applications will fall under the International Mechanical Code rules for equipment on roofs or the OSHA design guidelines for stairs and ladders. OSHA has many requirements for ladder and stair design but only two general requirements for how stairs and ladders should be applied in different situations. These are as follows:

  • 1910.23(b)(8) Ladders are used only for the purposes for which they were designed;
  • 1910.25(b)(8) Spiral, ship, or alternating tread-type stairs are used only when the employer can demonstrate that it is not feasible to provide standard stairs.

OSHA leaves it up to the employer to ensure that the use of a stair or ladder device is safe and appropriate in each application, so it is critically important for employers to understand the safety, feasibility, and usability of stairs and ladders in different applications. 

Roof Ladder Safety

For decades, fixed caged ladders and permanent ladders have been the standard device used for exterior roof access and mechanical access. But are these devices safe and user-friendly for workers? A study by the CDC estimates that approximately 20% of fall injuries involve falls from ladders and recommends several steps to preventing these falls including providing alternative, safer equipment for extended work at elevation. OSHA also recognizes the danger of caged ladders and in the 2017 Update to Walking-working Surface standards, introduced the requirement for ladder safety systems to be used with all ladders that extend more than 24 feet above a lower level. Cages are no longer allowed as a ladder safety system.

For additional safety measures OSHA also requires that 

1910.23(b)(11) Each employee faces the ladder when climbing up or down it;
1910.23(b)(12) Each employee uses at least one hand to grasp the ladder when climbing up and down it; and
1910.23(b)(13) No employee carries any object or load that could cause the employee to lose balance and fall while climbing up or down the ladder.


With these requirements, maintenance workers are forced to rope tools or other service equipment up and down rather than being able to carry them, making ladders very burdensome for workers. 

How to Choose the Right Stair or Ladder

So is there a better alternative? The answer is yes. In  almost all cases stairway systems are safer, more comfortable, and more efficient to use for workers than ladders. But the type of stairway that can be used depends on the specific roof access application. Common roof access applications include:

  • Roof hatch access
  • Accessing a roof from the ground
  • Accessing different elevations of a roof system
  • Accessing equipment on rooftops
  • Crossover stairs over a roof parapet

Roof Hatch Access

The exception to IBC 1011.12 permits access to the roof from the top story to be by an alternating tread device, a ships ladder, or a permanent ladder. Of these options, the alternating tread stair has been demonstrated to be the safest, most comfortable device. Using the alternating tread stair with roof hatches is very common for this application. 

Accessing a roof from the ground

For accessing a roof from the ground, the safest, most user-friendly alternative of a ladder system is a self-supporting standard stair system.  Standard stairs are designed with adequate tread depth for safer, more comfortable use than ladders and steep stair devices and can be self-supporting, bolted, and factory finished for easy installation. Workers can carry tools up and down and do not need to be harnessed into a ladder safety system. 

stair tower system

The downside of a standard stair system is that they can be costly and require a large amount of floor space. A self-supporting, alternating tread stair system is a cheaper, smaller layout and user-friendly alternative to a standard stair system. Alternating tread stairs provide more usable tread depth than ships ladders and can be descended face forward. Workers can carry items up and down without harnessing into a ladder safety system.  These systems can also be attached to and supported by the building structure.

Alternating tread stair roof tower system

Accessing different elevations of a roof system

For accessing roof systems from one elevation to another, since the stair system will be located on  the roof structure, you may need a lightweight and space-saving alternative. Aluminum alternating tread stairs are lightweight and shown to be the safest, most comfortable steep angled stair for these applications. These stairs can also be integrated with aluminum or galvanized steel platforms for accessing rooftop equipment. 

aluminum alternating tread stairs roof access


Roof Equipment Access

Standard prefabricated metal stairs are great options for equipment access on rooftops. Standard stairs designed to meet IBC or OSHA requirements allow for the easiest and most comfortable ascent and descent for maintenance workers. Alternating tread stairs with integrated equipment platforms are the best alternative for HVAC and air handling equipment access requiring a steep angled stair. testimonial_silentaire03

Crossover stairs over a roof parapet

Finally for crossover stairs for roof parapets, standard roof crossover stairs are the best option. If there is not room for a standard crossover stair, alternating tread stair crossover systems are the second best option. 

roof parapet crossover stair

Choosing the right stair for roof access is critically important for employers to provide roof workers with safe and efficient means of accessing rooftop locations. By following these guidelines you can be sure that the device you choose is the safest and most user-friendly for each type of roof access application.