Large Stair unit - Best way to build?

Hi all-- in the process of designing a stair unit--

The top tread will be at 88" height and will be 48" wide-
The bottom Tread will 16' wide. Tread depth is approx 1 foot. So basically I need 10 1 foot platforms. Its a big pyramid.

My thinking was to build a series of individually supported 2 foot platforms and have the intermediary step placed on top of that - But is there a better way to support the platforms than individually? If the treads weren't so deep I would consider stringers. But those would seem more trouble than they are worth here.

Any thoughts? These need to be rock solid as they will support 10-12 people at times.

Do they need to move on and off stage? Why not simply build them as a framed staircase unit?

Van said:

Do they need to move on and off stage? Why not simply build them as a framed staircase unit?

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Sorry - -I should have mentioned that....

They will be permanent -- attached to a large platform that does not move.

Off the top of my head, I would buy two of these and chop the top two steps off. Mount them on the far sides of your bottom 1' x 1' step. Then just add 2 x 12 treads and frame out the sides with 2 x 4 s for vertical supports and add luaun facing. If I get bored running sound for this rehearsal I'll draw something up.


Edit: Here is where I got before the end of their rehearsal.

TheaterEd said:

Off the top of my head, I would buy two of these and chop the top two steps off. Mount them on the far sides of your bottom 1' x 1' step. Then just add 2 x 12 treads and frame out the sides with 2 x 4 s for vertical supports and add luaun facing. If I get bored running sound for this rehearsal I'll draw something up.


Edit: Here is where I got before the end of their rehearsal.View attachment 14519

Click to expand...

I really appreciate you doing that -- I am so sorry for being so non specific... The base will be 16 feet -- Do you think I could expand the idea?

kjones9999 said:

I really appreciate you doing that -- I am so sorry for being so non specific... The base will be 16 feet -- Do you think I could expand the idea?

Click to expand...

Easily, if @TheaterEd doesn't get a chance perhaps I can throw together an example for you. Are the edges of the staircase curved/swept?

Just a reminder here:

(I would) make sure each step is individually supported, not in any way supported by steps further down. An installation contractor screwing that up was the root cause behind the Kansas City Hyatt disaster in the 90s.

I'm not sure that's applicable here, but some designs might go that way, so I figured I'd point it out.

Van said:

Easily, if @TheaterEd doesn't get a chance perhaps I can throw together an example for you. Are the edges of the staircase curved/swept?

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No its very much like what TheatreEd had drawn, just inverted and wider.

Jay Ashworth said:

Just a reminder here:

(I would) make sure each step is individually supported, not in any way supported by steps further down. An installation contractor screwing that up was the root cause behind the Kansas City Hyatt disaster in the 90s.

I'm not sure that's applicable here, but some designs might go that way, so I figured I'd point it out.

Click to expand...

Thats a good point. Do you think it would be dangerous if two steps were on the same support?

kjones9999 said:

Thats a good point. Do you think it would be dangerous if two steps were on the same support?

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Not as long as the support knew it was coming.

The problem in KC was that 2 decks were supposed to be supported from a threaded rod, independently. What got built was that the lower deck was supported from the upper deck, and the nuts weren't up to the load of both decks; Wikipedia has lots of nice detail.

Jay Ashworth said:

Not as long as the support knew it was coming.

The problem in KC was that 2 decks were supposed to be supported from a threaded rod, independently. What got built was that the lower deck was supported from the upper deck, and the nuts weren't up to the load of both decks; Wikipedia has lots of nice detail.

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It wasn't the nuts so much as the eccentric loading. I had a long conversation with one of the experts that investigated it. The relevant lesson was that it was designed correctly, and then the designers were let let go - to save money - and the contractors changed the detail. Even though they were not paid to review submittals or the actual work, the designers were sued and lost and went out of business. Second lesson, beware of design build contracts. Much better to have design eyes on the work than just the contractor's who's number one concern is their profit.

kjones9999 said:

Hi all-- in the process of designing a stair unit--

The top tread will be at 88" height and will be 48" wide-
The bottom Tread will 16' wide. Tread depth is approx 1 foot. So basically I need 10 1 foot platforms. Its a big pyramid.

My thinking was to build a series of individually supported 2 foot platforms and have the intermediary step placed on top of that - But is there a better way to support the platforms than individually? If the treads weren't so deep I would consider stringers. But those would seem more trouble than they are worth here.

Any thoughts? These need to be rock solid as they will support 10-12 people at times.

Click to expand...

88" - 10 treads - 8.8" per rise? This is a dangerously high step. Normally 7" maximum is considered the highest rise permitted, and research shows falls diminish a lot at around 6.4 to 6.5". In other words 7" is not good design, but code maximum. Good design is in the 6.5" range. 8.8" is in the range of check your liability.

BillConnerFASTC said:

88" - 10 treads - 8.8" per rise? This is a dangerously high step. Normally 7" maximum is considered the highest rise permitted, and research shows falls diminish a lot at around 6.4 to 6.5". In other words 7" is not good design, but code maximum. Good design is in the 6.5" range. 8.8" is in the range of check your liability.

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This however, is a Scenic piece and not open to the Public.

Van said:

This however, is a Scenic piece and not open to the Public.

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Did you forget OSHA? And if it's occupied - by performers or technicians or the public - it is required by law to meet building and fire codes. The person's means of egress at the middle of those stairs is either up or down those stairs and law requires every occupant be provided with a means of egress.

Ob:

If you have extra depth to work with I would add 2 more steps so you end up with closer to a 7" rise (or at least 1 so you get to an 8" rise, makes the construction math way easier). In most of the places I've worked (educational, commercial, and non-profit theatres) 8" rise steps are pretty standard, but I'll leave the OSHA and code stuff to Bill and others who know more than me. You didn't mention what sort of production situation you have, so it's unclear what applies to you. Ultimately it's up to you and your insurance company how you decide to apply the code and what your liability is.

From a construction standpoint, with an expectation of 10-12 people on the unit I would build this with 2x4 studwalls- 3 in the center supporting the full depth of the staircase, 2 built at an angle to support the ends of all of the steps, and others as needed to make sure each step is supported every 2' down to the ground(assuming you use 2x12 or doubled up 3/4" ply for the treads). Add a bunch of x-bracing and railings (!) and you should have a solid piece that'll support what you need. Something like the attached drawing could work, provided you make sure you're using appropriate fasteners, metal ties, and be really liberal with that bracing both along the axis of the studwall and along the axis of the steps.

Good luck!

kjones9999 said:

I really appreciate you doing that -- I am so sorry for being so non specific... The base will be 16 feet -- Do you think I could expand the idea?

Click to expand...

Lol, Totally read that backwards. That's what I get for multi-tasking. Makes WAY more sense now! I have three rehearsals to sit in on today, so If I have time I'll get on it.


EDIT: I had Time....

I agree that 8.8" steps are too tall, plus I prefer to use pre-fab stringers which if you use 2 x 12 treads will give you an 8" first step and 7" steps after that. With a 12 step staircase like I've mocked up here you will get to 85" so add an extra 2 x 12 to the base and another on top and you're there. Also, I was being lazy so I made the top step 4.5' feet that way the bottom can be 16' and just lose a foot each step instead of 13". What can I say, if a director came to me with those initial specs, this is what I would counter with. If you NEED to a dimension then obviously do what you have to do SAFELY.

I've placed a stringer every 2' in this mock up, I would want to support the other steps with vertical supports and proper bracing, but personally I'm the type to model and build the big parts and figure out the bracing once it's built.

Note, this thing is going to be heavy, but super stable. Working for a high school, I tend to over build things since you never know how they will be abused once built.

Just dawned on me, if anyone wants to make edits, here is the sketchup file. Also note, I'm figuring this software out on my own so I am by no means an expert. I just started mocking up my sets like this back in fall of 2015. Before that I was using graph paper and my director had a really hard time picturing what I was talking about. This has really helped us in being on the same page throughout the rehearsal / build process.

Can you tell I'm bored in the booth today? So, here are my last two big staircase projects. First we have an angled staircase that was needed for Cinderella. Unfortunately, it was not fully complete until the day of the show and I forgot to get a 'finished product' picture (I actually almost always forget that....) Anyways, here is a picture of it from the final dress.

This one actually had to roll on and off stage, that was a fun challenge that CB helped me solve actually.

Last year we had another project that involved a 45' wide five step stair case, and two ten step staircases.
Here is a link to the construction video, and below is a picture of the Sketchup model.