Building a stage with minimal supports

[Russell Reed]

Hey,

We are trying to build a stage that we can use to store a piece underneath. It will go in our black box and be about 2.5 feet tall. Here is the challenging part, there needs to be a 12' x 12' unobstructed area underneath for storage of a piece that cannot be taken apart. The goal is to make a stage that is 24' wide and 16' deep. How would we go about safely building something like this? What material to use for framing and plywood thinness? I was thinking to approach it like we are building 4'x8' platforms and to bolt them together to make the stage without supports.

Thanks,
Russell

 

[josh88]

You're going to need some seriously beefy framing to get 12 feet unsupported and have it not bounce like a trampoline or a drum. Bolts and regular 4x8's aren't going to be enough and all of those breaks are going to be weak points.

 

[BillConnerFASTC]

Forget the part of the fire code that doesn't allow storage under stages - portable or otherwise. I get it - codes are like badges - we don't need no stinking code. After that you could easily span the 12+' with a stressed skin panel. Just needs to be engineered correctly and then constructed. If you really need 12' clear, build 4 X 16' panels and knee walls at long edges and 2' in from long edges. It will still be a nice stage even after you're told to remove the item stored there by fire marshal.

 

[Van]

I've spanned 16' clear with a stressed skinned platform frame with 2x4, 3/4 A/C on top 1/2" A/C on bottom, 'studs' 14" O.C. Did not have any issues with deflection. Bill's the authority on Fire codes, but if there is an issue with storage of a set piece under this temporary stage, despite it being temporary and after proper flame retardant treatment, I'd look into installing a fire suppression system such as is used in smoke hoods. there are several options which I've used in the past the utilize what looks like a standard fire extinguisher with a sprinkler head on it. I installed these once in a scenic pass-through whose top doubled as a playing space in the audience and once in a 'Santa House' inside a mall they were recommended and approved by local Fire Marshall staff and were not too expensive.
Bill might have a better idea of what it is I'm refereeing to, I can't remember how they were described by the suppliers.

 

[BillESC]

You could also consider truss sections for the required span.

 

[lwinters630]

Hey,

We are trying to build a stage that we can use to store a piece underneath. It will go in our black box and be about 2.5 feet tall. Here is the challenging part, there needs to be a 12' x 12' unobstructed area underneath for storage of a piece that cannot be taken apart. The goal is to make a stage that is 24' wide and 16' deep. How would we go about safely building something like this? What material to use for framing and plywood thinness? I was thinking to approach it like we are building 4'x8' platforms and to bolt them together to make the stage without supports.

Thanks,
Russell

Don't even think of bolting them. In a strange way you can think of this is as building a house. A 2x10 floor joist will span 12 feet at 16" oc , live load is about 100 psf. Use 2x10-6' each side to finish to 24' wide. add 2x10 -6' long joist. Box headers all around as you would when building a house.

Consider using 16' long knee walls locating studs directly below the joist. Start first knee wals 6' each side of center line and the last ones on the outer ends. Add cross bracing both directions of the knee walls as well as between them. Using 1/2" plywood sheeting on outside corners of knee walls help.

Build the deck out 4x8 sheet- 3/4 plywood smooth side up on the deck and stager joints Run the first row of plywood full sheet purpendicular to joists. Cut next sheet. Use the cut off to start with a half sheet of plywood, then full sheets. Continue to a finished deck of 16' x 24'. Staggering joints will tie and strengthen top deck of stage platform.

 

[bobgaggle]

Seems like this question has been answered several times, but just to clarify, is this a set piece that is used during the show? like, the deck lifts off and now we see the swimming pool/sand pit thing? Or is it: hey we used this set piece in the last show, and want to use it 2 shows from now, but it can't come apart to get out the door so for the current show we're going to build a deck over it? Is the 'piece' stout enough to land some legs on it and just platform as usual with stock 4x8s?

 

[JacobRothermel]

+1 for a stress skin. Van's version w/ 2x4, 3/4" ply & stringers on 14" o/c is one good way; I've done 2x6 and skinned w/ 1/2" AC ply (centers on 16") before on odd shapes and gotten no deflection. Span was more than 12ft (can't recall what the actual span was). Strangely, I've never done just a rectilinear stress skin before...they're always weird shapes...

I'm no expert on fire code(s) but if you're doing this for a show, I don't see it being a problem for the marshal (temporary structures clause is a godsend); but if it's for storage storage, then yeah - you'll need to work w/ the fire marshal or an FPE to get it to code. Bill may (and rightly, he's the expert) disagree with me on this.

-jake

 

[BillConnerFASTC]

A piece of scenery used in that show - unlikely an issue. If this is a platform or stage in the sense it is semi-permanent (fire code temporary is just 30 days) and this is storage not todo with show - could become and issue.

You generally can get away with thinner ply on bottom of stress skin than on top. Stringer spacing is primarily dependent on the thickness of the top ply, keeping it from buckling. Performer use and the sound of foot fall my also dictate top ply thickness, though that becomes a non-issue with a solid foam or honeycomb core.

 

[mbrown3039]

A piece of scenery used in that show - unlikely an issue. If this is a platform or stage in the sense it is semi-permanent (fire code temporary is just 30 days) and this is storage not todo with show - could become and issue.

^^^ What he said. The other option is that you sprinkler it -- then you can store whatever you want for however long you want. But that's probably about $25K, lol. m