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Alternating Tread Stairs

This stair solves:

  • Alternating Tread Stairs (alternating tread ladders) for rooftop access, mezzanine access, or crossover obstacles
  • Four types of Alternating Tread Stairs (alternating tread ladders): walk-thru, to roof hatch access, to a platform, or crossover with a platform in the middle
  • Uses less floor space (footprint), if not feasible to use standard stair
  • Easier climb than a vertical ladder
  • Users can face the direction of travel for ascent or descent

Reduce Costs and Increase Quality

Reduce maintenance costs by using an aluminum stair which is naturally corrosion resistant with minimal ongoing maintenance or upkeep compared to steel stairs that corrode over time.  Reduce installation costs by using an aluminum stair which is a third the weight of steel, so it is easier to install, requiring less equipment.  Aluminum is high strength and is used in planes, cars, trucks, buses, trains, and buildings.  

Reduce Risks

With over 75 years of experience providing access solutions, we know the codes and are experts in this area.  Units are built to meet or exceed OSHA 1910 Subpart D design criteria.  Without the correct stair, there could be injury, liability, and loss of money, which puts companies' reputations and lives at stake.  

Aesthetically Pleasing and Sustainable Material

The standard aluminum mill finish will not rust or stain the surrounding structure.  Powder Coating is available to match the surroundings or stand out for safety. Clear Anodizing is available to increase corrosion, abrasion, and wear resistance.  In addition, aluminum is 100 percent recyclable and retains its properties indefinitely.  

Key Details of Stair

  • Fully Welded construction used throughout
  • 10" x 1/4" aluminum flat bar center stringer
  • 3" x 2" x 1/8" aluminum tubing side stringers
  • Treads are bar grating both welded and bolted to the center stringer, welded to side stringers
  • 1000-pound load capacity
  • Handrails on both sides, 1-1/4" Sch 40 Aluminum Pipe
  • 68 or 56-degree pitch
  • Tread widths of 11-7/8" for walk-thru stairs and 9-7/8" for hatch access stairs
  • Tread depths of 9-13/16" for 68-degree stairs and 11" deep for 56-degree stairs
  • Ladder Safety Post available for roof hatch exit
  • 5 Year Warranty
  • SECTION 05 51 33.23




    A. Aluminum Alternating Tread Stairs.


    A. Section 05 12 00 - Structural Steel Framing: Roof structure and opening support.

    B. Section 05 55 00 - Metal Stair Treads and Nosings: Miscellaneous metal supports.

    C. Section 06 10 00 - Rough Carpentry: Roof framing and opening support.

    D. Section 07 42 00 - Wall Panels: Roof curb flashing.


    A. OSHA 1910.25: Stairways.


    A. Submit under provisions of Section 01 30 00.

    B. Manufacturer's data sheets on each product to be used, including:

    1. Preparation instructions and recommendations.

    2. Storage and handling requirements and recommendations.

    C. Shop Drawings for Stairs:

    1. Plan and section of stair installation.


    A. Store products in manufacturer's unopened packaging until ready for installation.

    B. Store stair until installation inside under cover. If stored outside, under a tarp or suitable cover.

    1.6 WARRANTY

    A. Limited Warranty: Five years against defective material and workmanship, covering parts only, no labor or freight. Defective parts, if deemed so by the manufacturer, will be replaced at no charge, freight excluded, upon inspection at manufacturer's plant which warrants same.



    A. Acceptable Manufacturer: Precision Ladders, LLC, which is located at: P. O. Box 2279; Morristown, TN 37816-2279; Toll Free Tel: 800-225-7814; Tel: 423-586-2265; Fax: 423-586-2091; Web:

    B. Requests for substitutions will be considered in accordance with provisions of Section 01 60 00.


    A. Aluminum Alternating Tread Stair and Components: Stair, mounting brackets and handrails on both sides.

    1. Model: Model AT -*** (***= vertical height in inches) Aluminum Alternating Tread Stair as manufactured by Precision Ladders, LLC.

    2. Capacity: Unit shall support a 1,000 lb (227 kg) total load without failure.

    3. Degree of Incline: 56 or 68 degrees.

    4. Performance Standard: Units designed and manufactured to meet or exceed OSHA 1910.25.

    B. Components:

    1. Stair Side Stringers: 3 inch by 2 inch by 1/8 inch (76 mm by 51 mm by 3 mm) extruded 6005-T5 aluminum tubing. Pitch: 56 or 68 degrees.

    2. Stair Center Stringer: 10 inch by 1/4 inch (254 mm by 6 mm) extruded 6005-T5 aluminum flat bar. Note: Neoprene trim adhered to front edge of center stringer to protect climber.

    3. Stair Treads: 1 inch aluminum Bar Grating, 9 13/16” (249 mm) deep by 9 7/8”(250 mm) wide on hatch-access models (11 7/8” (302 mm) wide on Walk-thru models).

    4. Stair Mounting Brackets: 6 inch by 1/4 inch (153 mm by 6 mm) aluminum flat bar

    5. Handrails: 1-1/4 inches (32 mm) Schedule 40, 6005-T5 aluminum pipe provided with internal aluminum fittings.

    6. Finishes:

    a. Standard: Mill finish on aluminum stair components.

    b. Optional Finishes

    1. Powder Coated

    2. Clear Anodized


    A. Completely fabricate stair ready for installation before shipment to the site.



    A. If substrate preparation is the responsibility of another installer, notify Architect of unsatisfactory preparation before proceeding.

    B. Examine materials upon arrival at site. Notify the carrier and manufacturer of any damage.


    A. Install in accordance with approved submittals.


    A. Protect installed products until completion of project.

    B. Touch-up, repair or replace damaged products before Substantial Completion.


Technical specification
  • Unique ref.alternating-tread-stairs
  • Collection setStairs
  • CollectionAlternating Tread
  • TypeObject (single object)
  • Date of publishing2021-08-26
  • Edition number1
  • Material mainAluminium
  • Designed inUnited States
  • Manufactured inUnited States
  • BIMobject CategoryConstruction - Stairs
  • IFC classificationStair
  • Uniclass 1.4 CodeL4322
  • Uniclass 1.4 DescriptionStairs
  • Uniclass 2.0 CodeEE-30-10
  • Uniclass 2.0 DescriptionOn-Ground Stairs
  • Uniclass 2015 CodeEF_35_10
  • Uniclass 2015 DescriptionStairs
  • NBS Reference Code30-10
  • NBS Reference DescriptionOn-Ground Stairs
  • CSI MasterFormat 2014 Code05 51 00
  • CSI MasterFormat 2014 TitleMetal Stairs
  • OmniClass Number23-17 23 17
  • CSI UniFormat II CodeC2010
  • CSI UniFormat II TitleStair Construction