How To Build A Ships Ladder

Alternating tread stairs, ships ladders, and ship stairs are all steep angled stair devices used in infinite-restricted applications. How practise these devices differ from each other? OSHA and IBC define and set standards for the dissimilar designs of steep stairways . This guide volition aid you understand the dissimilar designs and code standards, and help you lot make the correct conclusion in choosing the safest, code-compliant selection.

Table of contents

• • Types of ship ladders & stairs (& pattern specifications)
  • Alternate tread ships ladder design specifications
  • What are alternating tread ships ladders?
  • Osha alternating tread ships ladder standards
  • IBC alternating tread ships ladder code requirements
  • Ships ladder design specifications
  • What are ship ladders?
  • Osha ships ladder standards
  • IBC ships ladder code requirements
  • Ship stairs pattern guidelines
  • What are ship stairs?
  • Osha transport stairs standards
  • IBC ship stairs code requirements
  • Ship stairs & ladders: Which is the right choice for you lot?
  • Alternating tread device vs ships ladder

Types of ship ladders & stairs (& pattern specifications)

The 2 nearly common types of steep angled stair devices for infinite constrained applications are alternating tread stairs and ship stairs or ships ladders.

OSHA Section 1910.21(b)  defines send stairs ( ship ladder ), and alternating tread-type stairs:

Send stair  (ship ladder) means a stairway that is equipped with treads, stair rails, and open up risers, and has a slope that is between fifty and 70 degrees from the horizontal.

Alternating tread-type stair  means a type of stairway consisting of a series of treads that usually are attached to a center support in an alternate manner such that an employee typically does non have both anxiety on the same level while using the stairway.

Alternating tread ships ladder design specifications

Alternating tread stairs use a staggered step pattern to increment tread depth at steep angles to salve space. This design allows for a safer, confront-forward descent down the stair.

The video demonstrates the difference in walking down an alternating tread stair next to a steep stair. The increased tread depth gives the user a consummate surface to residuum each stride.

What are alternating tread ships ladders?

Alternating tread stairs are a type of ships ladder or ship stair device. They are used in applications with space constraints to relieve floor space. Typical applications for alternating tread stairs include conveyor and equipment access, work platforms, crossover stairs, and anywhere in a facility that does non have infinite for a standard stair design.

OSHA defines Alternating tread-type stair as a blazon of stairway consisting of a series of treads that usually are fastened to a center support in an alternate manner such that an employee typically does non have both feet on the aforementioned level while using the stairway.

2018 International Building Code (IBC) defines an Alternating tread device equally a device that has a series of steps between 50 and 70 degrees from horizontal, ordinarily attached to a eye support rails in an alternating style so that the user does not accept both feet on the same level at the same fourth dimension.

Osha alternating tread ships ladder standards

OSHA set the design requirements for alternate tread stairs in section 1910.25(f) below:

• 1910.25(f)(ane) Have a series of treads installed at a gradient of l to 70 degrees from the horizontal;
• 1910.25(f)(ii) Take a distance betwixt handrails of 17 to 24 inches (51 to 61 cm);
• 1910.25(f)(3) Have a minimum tread depth of eight.5 inches (22 cm); and
• 1910.25(f)(iv) Take open risers if the tread depth is less than 9.5 inches (24 cm);
• 1910.25(f)(5) Have a minimum tread width of 7 inches (eighteen cm), measured at the leading edge of the tread (i.e., nosing).

OSHA 1910.28 also requires that alternate tread stairs and ship stairs have handrails:

• 1928(b)(11)(three) Each ship stairs and alternating tread type stairs is equipped with handrails on both sides.

The side mounted handrails besides act as the guardrail fall protection for the device. Because they have an integrated side-mounted hand / guardrail, alternating tread stairs practise non need to be used with fall arrest systems.

OSHA also sets standards for how an alternate tread stair tin can be used by employers.

• OSHA §1910.25(b)(viii) Screw, ship, or alternate tread-type stairs are used only when the employer can demonstrate that it is not feasible to provide standard stairs.

Usually, alternating tread stairs or ship stairs are used when there are infinite restrictions that get in non feasible to provide standard stairs.

Considering alternating tread stairs have a full usable tread surface for each human foot, the stairs are designed to be descended face-forward like a standard stair. They are not field of study to the requirements of OSHA 1910.23 Ladders for facing the ladder (backing down the ladder) while climbing. The face-forrad descent allows users to see in the direction of travel and more easily carry tools or items while descending.

IBC alternate tread ships ladder code requirements

IBC blueprint requirements for an alternating tread device are found in section 1011.14.ii:

Alternate tread devices shall have a minimum tread depth of 5 inches, a minimum projected tread depth of 8 ane/two", a minimum tread width of seven inches, and a maximum riser height of 9 1/ii." The tread shall exist measured horizontally betwixt the vertical planes of the foremost projections of the side by side treads. The riser peak shall be measured vertically between the leading edges of next treads. The riser peak and tread depth shall consequence in an bending of ascension from the horizontal of between 50 and lxx degrees.

IBC also has strict requirements for how alternating tread stairs can be used every bit a means of egress.

IBC Section 1011.fourteen states that Alternating tread devices are limited to an chemical element of a ways of egress in buildings of Groups F, H, and S from a mezzanine not more than then 250 square feet in area and that serves not more than five occupants; in buildings of Grouping I-3 from a guard tower, observation station or control room not more than 250 foursquare anxiety in area and for admission to unoccupied roofs.

IBC also allows an exception toIBC 1011.12then that access to the roof from the top story is permitted to be by an alternating tread device, a ships ladder, or a permanent ladder.  Too, the exception to IBC 1011.12.2 allows admission to unoccupied roofs to exist a roof hatch or trap door.

So for unoccupied roofs, a ladder or alternate tread stair extending through a roof hatch is the most common method of accessing the roof.

Ships ladder design specifications

Ships ladders are steep angled stair devices with angles between 50 and 70 degrees. This is much steeper than the typical angle of stairs of 45 degrees per OSHA and 30-32 degrees per IBC. Because they are so steep, ships ladders accept much less usable tread depth than a standard OSHA or IBC stair design.

What are ship ladders?

Ship stairs and ship ladders are addressed past both OSHA and IBC. OSHA uses the terms ship stair and ship ladder interchangeably while IBC uses the term ships ladder. OSHA requires that all ladders between threescore and 90 degrees exist device-facing, and so whatsoever ships ladder that is angled lx degrees or steeper must be descended backing downwards.

OSHA defines a ship stair in department 1910.21(b) as:

"A stair that is equipped with treads, stair runway, and open up risers, and has a slope that is between 50 and 70 degrees from the horizontal."

In essence, a ship stair is just a very steep stair. This prototype below from OSHA 1910.25 - Stairways  shows two send stairs at unlike angles.

Osha ships ladder standards

OSHA provides the ship ladder standards in section 1910.25(east) below:

• 1910.25(e) Ship stairs. In addition to paragraph (b) of this section, the employer must ensure send stairs (come across Figure D-ix of this section):
• 1910.25(eastward)(1) Are installed at a gradient of fifty to 70 degrees from the horizontal;
• 1910.25(eastward)(2) Have open risers with a vertical rise between tread surfaces of vi.5 to 12 inches (17 to 30 cm);
• 1910.25(east)(iii) Have minimum tread depth of 4 inches (10 cm); and
• 1910.25(e)(iv) Accept a minimum tread width of 18 inches (46 cm).

OSHA also defines angles for each type of stairway and ladder. Here is a chart comparing the angles of all the unlike types of stairs.

Angle	Type
≤ 30°	Ramp
xxx° - l°	Standard Stairs
fifty° - 70°	Transport Stairs
50° -70°	Alternating Tread-Type Stairs
60° - ninety°	Ladders

Like the alternating tread stair, OSHA 1910.28 also requires that transport stairs have handrails:

• 1928(b)(11)(3) Each ship stairs and alternating tread type stairs is equipped with handrails on both sides.

The side mounted handrails also act every bit the guardrail fall protection for the device. Considering they have an integrated side-mounted manus / guardrail, ships ladders exercise not demand to be used with fall arrest systems.

OSHA as well sets standards for how ships ladders can be used by employers.

• OSHA §1910.25(b)(eight) Spiral, ship, or alternating tread-type stairs are used simply when the employer tin demonstrate that it is not feasible to provide standard stairs.

Since ships ladders accept very narrow tread surface, they must typically be descended backwards like a vertical ladder. When backing down a ladder, OSHA requires that users use at least one hand for grasping and practise not carry tools or items that can cause loss of rest.

• 1910.23(b)(12)Each employee uses at least one manus to grasp the ladder when climbing upward and downwards information technology; and
• 1910.23(b)(xiii) No employee carries any object or load that could cause the employee to lose balance and fall while climbing up or down the ladder.

IBC ships ladder code requirements

IBC addresses ships ladder pattern in section 1011.xv:

1011.15.i Handrails of ships ladders

Handrails shall be provided on both sides of ships ladders. And per 1011.15, the minimum clear width at and beneath the handrails shall exist xx inches.

1011.xv.2 Treads of ships ladders

Ships ladders shall accept a minimum tread depth of v inches (127mm). The tread shall be projected such that the total of the tread depth plus the nosing projection is not less than viii 1/2 inches (216mm). The maximum riser height shall be 9 ½ inches (241 mm).

IBC also sets strict standards for how ships ladders can be used as a means of egress.

IBC section 1011.15 Transport Ladders states that ships ladders are permitted to be used in Group I-3 as a component of a means of egress to and from command rooms or elevated facility observation station not more 250 foursquare anxiety with non more than three occupants and for access to unoccupied roofs.

Ship stairs blueprint guidelines

Ship stairs and ship ladders (or ships ladder) are terms ofttimes used to mean the aforementioned type of device. OSHA uses the term transport stair while IBC uses the term ships ladder. The blueprint requirements are the same for ship stairs as they are for ships ladders no matter the terminology.

What are ship stairs?

What is the divergence between a send stair and a ship ladder?

A key difference between a stair and a ladder is the way in which they are used. OSHA 1910.23 states the following requirements on employees using ladders.

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 crusade the employee to lose rest and fall while climbing upwardly or down the ladder.

Stairways, transport stairs, and alternating tread stairs are not bailiwick to these requirements. Stairways and alternating tread stairs can both be descended confront forward in the management of travel. Some send stairs can be descended face forwards depending on how steep the bending. The angles of ship stairs and ladders overlap betwixt lx and seventy degrees. Ship stairs tin can be as steep every bit 70 degrees, while ladders can be as shallow as 60 degrees.

Transport stairs shallower than threescore degrees can be designed as face-forward descent devices. Yet, because these devices have much shorter tread depth, walking downward confront-frontwards is very difficult and potentially unsafe for the user. Users are left with a very small tread surface for each foot causing a autumn take a chance. Yous can see that in this photo below.

In many cases, bankroll down ship stairs is a safer alternative even though the user cannot run across where they are going while backing downward.

In the case of backing down ships ladders, employees should follow the same OSHA rules for descending ship ladders as for descending fixed ladders. Employees should apply at to the lowest degree one manus to grasp the ladder while backing downward and should non conduct objects while climbing the ladder.

How send stairs or ship ladders are designed to be descended is upwards to the designer or operator. Designers should consider that equally stairs go steeper, tread depth shortens and becomesa major hazard gene of stairway design. For standard ship stairs, a shallower bending is safer than a steep angle. Alternate tread stairs have the unused half of each tread removed to providemore tread depth at steeper angles.  These are all considerations that should be factored into your adjacent design.

For more info, download our guide on stair design for safety and ergonomics.

Osha transport stairs standards

Because OSHA uses the term ship stairs and ship ladder interchangeably, the OSHA standards for send stairs are the aforementioned as for ship ladders.

IBC ship stairs code requirements

IBC uses the term ships ladder rather than the term ship stairs. IBC does not refer anywhere in the code to the term send stair. The IBC code requirements for send stairs is the same every bit for ships ladders.

Ship stairs & ladders: Which is the right choice for you lot?

When choosing betwixt a standard stair, ship stair, or alternating tread stair, the most important consideration is prophylactic. Which stair pattern is the safest?

It helps to empathise the a few of the most important blueprint induced safety factors of stairway design as outlined in Affiliate xiii of Fall Protection and Prevention: Principles, Guidelines, and Practices.

• As tread depth becomes narrower than a foot length, missteps become more frequent. Shorter treads give insufficient foot support and crusade postural instabilities
• There may be no graspable, reachable handrail
• In that location may be a discontinuous handrail
• In that location may exist confusing colour patterns on the tread or poor visibility of nosings
• The nosing strip may project above the tread

Of these prophylactic factors, adequate stair tread depth is the most variable between the different stair design.

Here is a table showing the minimum tread depth requirements for the dissimilar stair types.

From this chart, you lot can meet that standard stairs have the nearly tread depth, followed by alternating tread stairs, followed by spiral stairs, and so transport stairs.

Alternating tread device vs ships ladder

How practise we know that tread depth is an important safety factor and that alternating tread stairs are safer than transport stairs?

Many studies take demonstrated that narrow tread depth is a run a risk factor for stairways. A contempo study measured the perceived difficulty in descent of stairways. This study, by Hisao Nagato, of the Ohara Memorial Institute for Scientific discipline of Labor in Japan, looked at how difficult it was for users to descend stairways with varying tread depths. The result showed that stairs become increasingly hard to descend as tread depth narrows. To measure the difficulty, the researchers used a metric called the Z-value, which increases equally difficulty increases. Beneath is a chart showing the Z-values for different stair designs. Send stairs were shown to accept very loftier perceived difficulty while descending due to the short tread depth.

Another study past  Virginia Tech Man Factors Engineering science Laboratory demonstrated that alternate tread stairs had 72% fewer missteps than ship stairs and were preferred by users. The participants in that written report also rated the alternating tread stairs higher for both prophylactic and comfort during descent.

Conclusion

The results are clear. The alternating tread stair is the safer, more than comfortable selection when it comes to space saving stairs. If you have express infinite and need a steep stair, choose the alternating tread stair.

FAQ

What angle is a ship ladder?

A send ladder angle is between 50 and 70 degrees. OSHA section 1910.25(east)(1) requires ship ladders to be installed at a gradient of 50 to 70 degrees from the horizontal.

What is an alternating tread staircase?

An alternating tread staircase is a blazon of steep, safety stair with a staggered step design. Alternating tread stairs take steep angles to save space. The staggered pace design increases the usable tread depth to provide the user a total tread surface on each footstep.

Are alternating tread stairs legal?

Alternate tread stairs are legal to install and employ in space-restricted areas under OSHA section 1910.25. Alternating tread-blazon stairs are used only when the employer can demonstrate that it is not feasible to provide standard stairs.

Source: https://blog.lapeyrestair.com/ships-ladder-stairs-code-requirements

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