Looking for pointers on how to leg platforms 8’ high while maintaining sturdiness

lardman

Member
I am a high school student, and this is my first year working in my school’s scene shop. I have a good understanding of framing and rough carpentry from work experience, but I am not sure about something that I want to pursue. I am currently designing the set for our next fall play, and I need to make two platforms, 8’ high. I was thinking that I could do two 4’x8’ stock platforms, and I could use 1x3 or 2x4’s to leg it 8’ high.

Is it recommended to leg these platforms this high? I’m not sure of any other ways to leg platforms that high while maintaining sturdiness and stability, so if I could have some pointers I’d greatly appreciate it.
 
Please don't use 1x3 if it's going to support life up there, and please have a competent adult help you with this in person.

Are we talking one 8'x8' platform (two 4x8s side by side) supported 8' up, or two separate 4x8s each that high? Can the supporting structure be fully enclosed, or do you need something like a doorway under there, or is it a porch roof that needs to be very open underneath, or what?

Railings, and access to the platform (stair? ladder?) must not be afterthoughts, and must not be compromised for "art".

Have a competent adult help you with this in person.

Support by compression, brace diagonals. Resting your plats on studwalls skinned in plywood is your most rock-solid and student-friendly-construction way to go. This is especially true if you have stock platforms built with drywall screws or other no-nos.

Have a competent adult help you with this in person.

Check your stock platforms for wear and defects before using in this kind of safety-critical situation. Re-framing them is cheap and fast if they show issues like cracks, or look like swiss cheese from years of screws and bolts. Or drywall screws.

Have a competent adult help you with this in person.

There are other cool ways to do this safely and elegantly, with additional time/money/equipment/skill.

Have a competent adult help you with this in person.

Totally doable, by students like you. You might design and build this perfectly all by yourself. It's just that if you have to ask (which is a great instinct) then that means you'd benefit from an in-person expert working with you, so I'd go find that person in addition to using this great resource that CB is.
 
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It would be one 8'x8' platform, supported 8' up. I do have someone who is able to look at the structure and will let me know what could be unsafe. I plan on adding escape stairs with a permanent railing off of the left side of the platform. I'm also going to add railings across the sides of the platforms. Safety of my actors and crew is of the utmost priority for these platforms. The supporting structure can be fully enclosed, I just need to come up with something sturdy for actors to come up onto from one of the wings. I have been looking at studwall platforms, and the yale triscuit 4x4 platform. I would like to do a studwall platform 8' high with triscuit platforms, but I can't seem to find any literature on using studwalls for tall applications. I am assuming if I did, I would need to cross brace it and add a horizontal toggle across the legging?

EDIT: I am also thinking about making it only 6' high.
 
It would be one 8'x8' platform, supported 8' up. I do have someone who is able to look at the structure and will let me know what could be unsafe. I plan on adding escape stairs with a permanent railing off of the left side of the platform. I'm also going to add railings across the sides of the platforms. Safety of my actors and crew is of the utmost priority for these platforms. The supporting structure can be fully enclosed, I just need to come up with something sturdy for actors to come up onto from one of the wings. I have been looking at studwall platforms, and the yale triscuit 4x4 platform. I would like to do a studwall platform 8' high with triscuit platforms, but I can't seem to find any literature on using studwalls for tall applications. I am assuming if I did, I would need to cross brace it and add a horizontal toggle across the legging?

EDIT: I am also thinking about making it only 6' high.
I second the idea of 6 ft high unless you have a really tall proscenium or working in a black box. When an actor can touch the top of a 16 ft flat....

As for design, will there be any dynamic loading? Dancing, prancing, jumping... anything more than actors walking and standing? How many actors at once?

Does the piece move on/off/around during the show, or can it remain stationary from curtain up to curtain down?
 
Please don't use 1x3 if it's going to support life up there, and please have a competent adult help you with this in person.
I'm surprised at the aversion to 1x3. Most scene shops I've done work in routinely leg up platforms that tall with 1x3 hog trough and bracing, It's also what I was taught in my college courses. Everything ive stood on always seemed plenty sturdy. I have seen some use drywall screws to affix legs and bracing as well, most of the people doing so explaining that "there are so many screws in total, it won't be an issue" (much less of a fan of that). I don't have much experience when it comes to carpentry or set building though, and would much rather learn this lesson the easy way than the hard way.
 
1x3 hog trough is pretty common, more so on platforms framed with 3/4" ply. Up at that height you're building stud walls, especially since he said it can be enclosed. I'd make 8 hollywood flats and use them as 'legs'
 
I leg up with hog troughs made out of one 2x4 and one 2x6 for anything over about 6'. Two 2x4s for anything under 6'. For platforms made out of 2x4 frame, don't try to span more than 4'. Each platform will need 6 legs, although I sometimes do 5 and 4 allowing the center seam to "share" legs.

Plenty of cross bracing is encouraged, although it depends on the stairs. The platform I just did for Joseph/Dreamcoat was 28' wide and 8' deep and had zero cross bracing because it had two stair units at 45 degrees and two escape stairs off the back at 90 degrees. In effect, the front had four sticks of 2x4 square steel tube angled to the deck and the rear had four 2x10 stringers angled to the deck. Screwed down with headlocks, that thing didn't budge. I toenailed the legs to the floor so an errant rolling scenic element or a running actor couldn't punch it off-plumb.

If you need a clear span, you're stuck with proper joisting and the stock platforms will have to stay in the shop. The piece I mentioned above had a clear span of 11' 3", so I had to frame it with 2x8s at 16" OC. Can't have 10 dancers pouncing around on 2x4s or 2x6s, especially with an orchestra underneath it.
 
If you are building Hog Troughs out of 1x3 the you are fine. You want diagonal supports as well as a box frame around the bottom of the feet. Depending on the maximum load I would also box frame the legs 48" OC ASF. Through-bolt legs to platform framing. 5 staples <like pips on a die> at every. overlap, like where the box framing goes over the leg.
Another option, but much more lumber involved, would be to make stud walls to two sides then cross brace those with Diagonal bracing, make sure you use blocking between the studs and add a cross brace, one on each stud wall, opposite of each other; Low to high, high to low. If you have any questions ask.
 
If you are building Hog Troughs out of 1x3 the you are fine. You want diagonal supports as well as a box frame around the bottom of the feet. Depending on the maximum load I would also box frame the legs 48" OC ASF. Through-bolt legs to platform framing. 5 staples <like pips on a die> at every. overlap, like where the box framing goes over the leg.
This is exactly what I was taught. I was worried I would have to un-learn everything I had previously considered ok.
 
It would be one 8'x8' platform, supported 8' up. I do have someone who is able to look at the structure and will let me know what could be unsafe. I plan on adding escape stairs with a permanent railing off of the left side of the platform. I'm also going to add railings across the sides of the platforms. Safety of my actors and crew is of the utmost priority for these platforms. The supporting structure can be fully enclosed, I just need to come up with something sturdy for actors to come up onto from one of the wings. I have been looking at studwall platforms, and the yale triscuit 4x4 platform. I would like to do a studwall platform 8' high with triscuit platforms, but I can't seem to find any literature on using studwalls for tall applications. I am assuming if I did, I would need to cross brace it and add a horizontal toggle across the legging?

EDIT: I am also thinking about making it only 6' high.
Think of it this way you are building a second floor of a house. So supporting walls 2x4 16" on center, placed under the ends of the floor joists. I would build stud walls under all 4 sides and put 1/2" Plywood on the face of all sides. Then set your decks on top. Bolt the two decks together. There are options of cross bracing instead of 1/2" plywood. Things to consider is the structural load for the span of your deck. You can look up the rating of 2x6 at 16" on center for 8' span. Use 3/4 plywood on top. See codes for stairs and railings. Consider pre-made stringers from big box, it's faster and easier.

I have seen some post suggesting 1x3. if you were under 24" tall maybe, But over that and I use knee-walls.

Attached are some clips of a High School version of Chicago. The full orchestra up on a 2x6 8' span decks about 7' off floor with 2x6 stud walls spaced 8' apart. Egress stairs were on each side up stage. Other clips shows front stairs opening.

Please consult someone with structural knowledge. I hope your show goes well.
 

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Good Lord it's been 15 years since I first posted my step by step photos of how I build my platforms. I don't use the sound deadening material in the platform construction any longer. It did help, but it wasn't a significant amount. At the time I was in a black box where every dB mattered. Today I'm on a big proscenium stage and it doesn't matter.

The stud wall leg technique remains my favorite. So strong. So sturdy. I have used this technique to build a platform 30' wide and 6' high with a "bridge" section at center and put 15 kids on top dancing without any movement issues. Yes, It's heavy. Yes it's over built. Yes you can do fancy, things with math, 1x, and triscuits that will be lighter. But I can pull stuff out of storage and have a 6' high platform up in an hour and I never think twice about if it can handle the load. 2x4 stud wall construction works now get off my lawn.

Here's the old thread. My platform system.
 
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Also I would argue that 2x4 and stud wall legs is the best technique for high schools. There are a lot of ways that beginning carpenters and beginning designers can screw up fancier techniques like triscuits, or using 1/2" ply, and 1x. The 2x4 and 3/4" approach is very forgiving for beginner construction skills and won't cause issues in 5 years when there's no one around who knows how to do the math for the fancier techniques.
 
Think of it this way you are building a second floor of a house. So supporting walls 2x4 16" on center, placed under the ends of the floor joists. I would build stud walls under all 4 sides and put 1/2" Plywood on the face of all sides. Then set your decks on top. Bolt the two decks together. There are options of cross bracing instead of 1/2" plywood. Things to consider is the structural load for the span of your deck. You can look up the rating of 2x6 at 16" on center for 8' span. Use 3/4 plywood on top. See codes for stairs and railings. Consider pre-made stringers from big box, it's faster and easier.

I have seen some post suggesting 1x3. if you were under 24" tall maybe, But over that and I use knee-walls.

Attached are some clips of a High School version of Chicago. The full orchestra up on a 2x6 8' span decks about 7' off floor with 2x6 stud walls spaced 8' apart. Egress stairs were on each side up stage. Other clips shows front stairs opening.

Please consult someone with structural knowledge. I hope your show goes well.
Massive overkill. If you supporting a couple thousand pounds through a 2-3 year long run. Maybe it would require this level of framing. Houses with 2nd stories were built, for YEARS with less ground floor framing. Given most HS budgets you want the most efficient system using the least amount of materials possible. There are tons of safety considerations to figure in, for sure, however the above describes using a battleship for lake fishing.

*** That may have come off a lot harsher than I meant it to be. I think you make very valid points. I have framed Operas with 5/4 before but those are designed to tour for 30+ years an support Brunhilde.
 
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Massive overkill. If you supporting a couple thousand pounds through a 2-3 year long run. Maybe it would require this level of framing. Houses with 2nd stories were built, for YEARS with less ground floor framing. Given most HS budgets you want the most efficient system using the least amount of materials possible. There are tons of safety considerations to figure in, for sure, however the above describes using a battleship for lake fishing.

*** That may have come off a lot harsher than I meant it to be. I think you make very valid points. I have framed Operas with 5/4 before but those are designed to tour for 30+ years an support Brunhilde.
My concern is dynamic loading, in particular any lateral forces on the top of the platform (dancing, skipping, jumping). Having watched videos of PIT COVERS, things presumably coming with engineering drawings and engineer's stamps on those, fail because they were used in a manner the designer did not anticipate.... I'm all for overkill in both materials and design. I probably lack the talent to explain to parents and administrators why it was better to save $500 in materials as the EMTs treat kids injured in a staging incident.

I've seen some really sketchy sets with students climbing/crawling all over them, and miracle of miracles, nothing bad happened that day. We take it down at the end of the run and see how many deck or sheetrock screws held the swiss cheese together and they swear they'll scrap it... and it comes back next year in another show. Bah AND humbug.
 

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