Ship Stairs: Alternating Tread Stairs, The Better Alternative
More useable tread depth makes alternating tread stairs safer and more comfortable to use.
Alternating tread stairs versus ship stairs
More useable tread depth makes alternating tread stairs safer and more comfortable to use.
✔ More tread depth
OSHA requires a minimum tread depth of 8.5" for alternating tread stairs. More useable tread depth means the entire foot is supported. §1910.25(f)
☓ Less tread depth
OSHA requires a minimum tread depth of 4" for ship stairs. Less tread depth means half of the foot is unsupported which is less stable. §1910.25(e)
Virginia Tech conducted a study comparing alternating tread stairs to ship stairs and concluded that alternating tread stairs have a clear comfort and safety advantage over ship stairs.
| Test subjects strongly preferred alternating tread stairs over ship stairs for safety and comfort: | |
| 89% | Chose for safer tread depth |
| 85% | Chose for more comfortable tread depth |
| 72% | Chose for safer ascent |
| 89% | Chose for more comfortable ascent |
| 82% | Chose for safer descent |
| 85% | Chose for more comfortable descent |
| More missteps occurred on the ship stair than the alternating tread stair: | |
| 72% | Chose for safer tread depth |
| 129% | Chose for more comfortable tread depth |
| Test subjects felt less safe and comfortable on the ship stair that than the alternating tread stair: | |
| 64% | Felt more likely to slip/trip on ascent |
| 85% | Felt more likely to slip/trip on descent |
The alternating tread stair study was conducted by the Department of Industrial Engineering at Virginia Polytechnic Institute and published in the proceedings of the Human Factors Society’s 32nd Annual Meeting, pp 981-984. View findings.
✔ More tread depth
OSHA requires a minimum tread depth of 8.5" for alternating tread stairs. More useable tread depth means the entire foot is supported. §1910.25(f)
☓ Less tread depth
OSHA requires a minimum tread depth of 4" for ship stairs. Less tread depth means half of the foot is unsupported which is less stable. §1910.25(e)