Alternating Tread Stairs

[John Pariseau]

Has anyone built/used alternating tread stairs, also known as "Jefferson stairs"? I've been putting in a second floor in my workshop, second floor will be accessed once a day, 140.5" from the first floor. Use will be dust-free hobbies, and for any "large equipment" I'd be lifting it via a hatch in the floor. Widest I can make the stairs is 30" due to building geometry.

First off, I've evaluated installing an attic ladder, and that just won't work. That leaves a normal set of stairs (likely with a 90 or 180 turn) or a compact alternating tread design. I've never used this style before, but I need to finalize my stair design (and build them) before continuing with my second floor decking. I would like to save as much floor space as possible.

There are companies that make these - though they indicate some circumstances aren't code compliant. Some big box stores sell a stair kit (and additional risers) in this design - from an Italian company.

Ignoring construction methods (as I would secure the treads better), this is the style I'm referring to:

https://www.ana-white.com/blog/2015/09/loft-stairs-alternating-tread-space-saving-stairs-loft

Any thoughts/suggestions would be appreciated.

[Jerry Bruette]

We have a similar but industrial system at work for going over conveyors. They're built by Lapeyre. You have to have a good grip on the handrails going up and especially down the stairs. They're a PITA if you want to carry something in your hands.

I really don't like them and we're only going up about half the distance you want to go. Hope you're note to old or have bifocals.

[Bill Dufour]

You will need solid handrails on both sides. I doubt code will allow a 30" stairway as the only access. A firefighter in full gear could not go up that narrow a space
Bill D

On Edit:
Talk to your insurance agent.

https://www.dir.ca.gov/title8/3231.html

[Rob Luter]

I’d fall and break my neck inside a week.

[Christopher Herzog]

I have worked in a facility with a set. They took some getting used to but once your mind adjusts it was fine.

[Jamie Buxton]

I don't think I'd be comfortable walking down those stairs with my back to the stairs. Instead, I'd turn around and back down those stairs, just like I'd do with a conventional ladder. With that in mind, I'd probably just use a conventional ladder instead. I'd continue the handrail for the ladder a good long ways above the second floor, so I have something firm to hold on to as I make that pivot to go down the ladder.

I'd also have couple of shopping bags at the top and the bottom of the stairs. When I want to carry little stuff up or down the stairs, I'd put it in a bag and sling the bag over my shoulder. That is, I'd have both hands free to hold on to the ladder.

[Paul F Franklin]

I have nothing first-hand to offer, but the Dec/Jan issue of Fine homebuilding has an article on safety and code issues around so called "irregular" stairs, which include the alternating tread type.

[John Pariseau]

I have nothing first-hand to offer, but the Dec/Jan issue of Fine homebuilding has an article on safety and code issues around so called "irregular" stairs, which include they alternating tread type.
Thanks! I just read the article, and it clarifies things quite a bit. I think now I understand in what circumstances the alternating design can be used.

[John Pariseau]

https://www.dir.ca.gov/title8/3231.html
If I'm reading it right, a 30" wide stairway is OK:


Private stairways serving an occupant load of less than 10 may be 30 inches wide.

I'd have to check MI code to be sure.

[John Pariseau]

And Michigan code does not list an exception for that occupancy level, though it is interesting CA allows for a narrower stair. I have one area I can put 34.5" stair in - wouldn't get me the full 36" but would be closer than 30.