Why is This Stairway / Ladder Designed Like This?

I vaguely remember seeing this at another site that had access to a flat roof that had a designed walkway above. I was told but did not see it used that a specialized tool used the staggered steps to lift and lower heavy items through the roof hatch.

Probably, the builders lack materials and used the left over cuts. But it's way better than monkey ladders.

It makes easier i think when 2 people carry a bulky thing to the roof.

It seemingly fits the song that goes like " wherever you go, I'll be 2 steps behind you" - Def Leppard

I have found that using one side or the other is just like climbing a step-ladder or stairs however, with one foot on either side and ascending the stairway you ascend quite slowly and it feels odd to be ascending only about 4" at a step. Maybe it is for the purpose of carrying or lifting heavy tools or equipment? I have yet to find someone that has either designed or specified a ladder like the picture.

This is a poor example of an alternating-tread stairway (or ship's ladder). As you note, the steps are much too small. One company that makes these is Lapeyre. I made one for the plant where I work. A Google search may turn up several architecturally beautiful and interesting examples.

(I responded before reading the intervening posts, which already mention all of this.)

I like that picture. It very clearly and succinctly illustrates the issue at hand with the slope and tread depth.

I like the green one. It highlights the fact that 50% of the stair tread is actually redundant!

There are 2 buildings that have steps like this one, but one of the other buildings has a set that has the alternating step that is approx. 16" which makes an 8" step rise.

I'm wondering if this stair was supposed to have half as many steps?

the picture makes the stairs looks wide.... but sometimes, it doesn't pay to figure out the reason why.

I've heard these called ships ladders - but now I see them called alternating-tread stairs. Yeah, the treads in your picture seem to be too close together. 16" making 8" rise per step sounds better. They're a little weird at first, but they're ok once you get used to starting with the rightcorrect foot. And you can come down them facing outwards.

I prefer the Bat Pole myself.

Lapeyre Stair-Alternating Tread Stairs www.lapeyrestair.com/products/atsAll.aspx ‎

Alternating Tread Stairs. The Lapeyre® Alternating Tread Stair features a unique
tread design which provides greater tread depth than vertical ladders or ship's...

see "how the alternating tread stair work" - can't append the picture.

I think what I'm most curious about is the "extra" tread in-between the other treads. The 4" step up is an odd height!

so people don't 'fall through'

space savings

Try coming down a steep stairway facing out, and you'll see the advantage here....it's a lot easier if you have to use the stair frequently, and space is confined...

Built with union labor.

Lyn,

On this, you are correct. The structure was built in the Las Vegas BOOM before it went "BOOM" and the development was all union labor.

What is the recommended angle(elevation),width & height of steps in a stair for kids,elders,adults?.

In the U.S.A., OSHA standard stairs have an angle between 35 and 55 degrees. Rise + tread = 17.5 inches is an acceptable formula, but is not mandated. Other architectural guidelines also exist, such as 2R + T = 25 or 26".

Alternate-tread stairs can be steeper than 55 degrees. They, and spiral stairs, are OSHA-allowable only as alternative stairs after any mandatory requirements are satisfied via standard stairs.

I think iTS a self made stairs made from left overs

As you get older, your ankles, knees and hips weaken, and taking high steps can be painful to extent that it could be difficult to climb ordinary domestic stairs. Replacing existing stairs with a lot more shallow risers but with the same tread width would only be possible with stairs designed like this. Notice the substantial double handrail.

But it could be for people with short legs - kids maybe - for access to a playroom.

Alternating tread stair. We sold them at work for our mezzanines, but I can't remember what brand--the actual treads were I bit smaller and rounded as I remember. Rise height was the same both left and right. Name came back! La-Pyre, but I probably spelled it incorrectly. For use where you have limited space for the rise and run.

Perhaps the key issue in stair design occurs when descending. The back of your leg must clear the step you are leaving, but the ball of your foot needs to land securely on the next step down. In this respect, too-small steps are almost worse than too-large steps. My town has some dumb contractor that makes 6" rise 8" tread stairs that are unsafe.

They were originally called ships ladders because they took up less space, a very important factor on ships where more available space is valuable. Deck space not used for a regular stair or is usually either more commercial income to be sold or more offensive weaponry space in military vessels. They are also used where a steep ladder and one that can be descended facing away from the ladder is needed. On a vessel bulkheads and hatches are used. The hatch between decks for a ships ladder is smaller in area and requires less deck space for it vs. a regular stair way.

They now have other names that mean the same thing. Ships stairs. alternating step stairs, alternating step ladder, etc. The term ships ladder is now used to indicate a stairs/ladder with a riser of 9" to 11", a tread run of 4" to 6", and an angle of 50^o to 70^o. OSHA even has a standard for them https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=25301

and Oregon http://www.cbs.state.or.us/osha/pdf/pubs/fact_sheets/fs34.pdf

A Ships Ladder does not have to be an alternating step ladder. Some advantages to alternating ones are they can be descended while facing away from the ladder and tools, etc. can be carried easily while descending. They can be full width tread ladders that are also called Ships Ladders. They are harder to climb/descend and must be used facing the ladder/stairs.

Good Luck, Old Salt

Here are some pix: http://www.houzz.com/alternating-tread

Those are some really nice designs!

I have seen this type of ladder on ocean going vessels and I believe it accomplishes two objectives:

Uses less stairwell space to attain a higher distance objective.

Provides more stable footing by maintaining standard maximum tread height design.

space savings