# Legs from a 4x8 platform 10' in the air



## Stephanie Ball (Aug 11, 2014)

If I'm putting a run of three 4x8's 10 feet in the air with stairs attached on each side, do I want 6 - 2x4's as legs on each platform (w/some cross bracing on the 4' ends), or do I want 6 4x4's as legs on each platform? I feel like 4x4's are over kill, but I'm not sure. Thanks!


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## rsmentele (Aug 11, 2014)

2x4 will work fine, you will just want to cross brace each side, not just the 4' side. You will also want to stop the cross braces at the midpoint and run another cross the opposite way on the bottom half..... I'm not sure if that is really clear... the point is, the 2x4 is strong enough, you just need to keep the legs from bowing or sliding out.


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## robartsd (Aug 11, 2014)

rsmentele said:


> the point is, the 2x4 is strong enough, you just need to keep the legs from bowing


 
I agree, at 10 foot length a 2x4 without bracing is most likely to fail by buckling.


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## Skervald (Aug 11, 2014)

You might want to consider making some or all of your legs using two 2x4s configured in an "L" shape. (narrow face of one attached to the wide face of the other) You'll still need appropriate cross bracing but that way,one 2x4 will support the other along the full edge and greatly reduce the chances of buckling, swaying, bowing, or sliding. (BSBS) Very important on a 10 foot tall platform.


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## theatricalmatt (Aug 11, 2014)

Even stronger than the above suggestion, you might want to consider building studwall rather than use legs. I usually use studwall at any height above four feet, and especially if I know there's going to be a lot of set, or a lot of dancers, on top of the platform.


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## SHCP (Aug 11, 2014)

I agree that stud wall, or a few more legs are a good idea at that height. Anything over 8' and I add plywood shear as well. Your staircases will help to add stability, but where the platforms meet or along a long span, it can't hurt to add perpendicular shear support.


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## Skervald (Aug 12, 2014)

I agree wholeheartedly with the above suggestions. You never know what a director is going to "just try" on a piece. I recently built a short platform I was told would need to support two standing actors. The director ended up putting 6 dancers on it. I'm often accused of overbuilding for a given purpose but I'd rather have that reputation that the opposite!


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## Christopher71188 (Mar 6, 2015)

Alright Everyone, so I have a question based off of this one. I am looking for the best way to leg platforms, specifically for my pit extension. The decks that we use are standard 4'x8' decks constructed of 3/4"ply, 2x4 Frame, then covered with sound board and Maso. I have typically done the stud wall style framing instead of individual legs, but my question is can I sill do this as I can not secure to the floor. I have done both "standard" Legs (bolted or screwed to the frame) and this stud wall style, and I typically find the stud wall to be more secure. This will be used to hold the audience for this particular show, as we are changing the proscenium stage into a black box style space. Any thoughts on this would be awesome! Thank You


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## TheaterEd (Mar 6, 2015)

I never screw my stud wall legs to the deck. the weight holds them in place well enough.

Be careful though. There have been several homemade pit filler failures in the news this past year.


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## Christopher71188 (Mar 6, 2015)

Thank you for the reply, I have always screwed them to the deck. I was never sure if it was really needed or not, but figured you ramset them well building a house to it couldn't hurt.

I am aware there have been many failures in the past year, rather scary. This is why I was looking for the best way to leg and support. All things I got to start thinking of when the director goes "ok were having everything on stage, and the audience can sit on stage just build out the extension like we usually do"


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## robartsd (Mar 6, 2015)

You need to prevent the bottom of the stud walls from moving relative to each other (the attached platform restricts relative movement of the tops). Diagonal bracing between the top and bottom of adjacient walls will do this.


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## RickR (Mar 6, 2015)

Just for clarification: Don't screw the legs to the decking surface (plywood), do attach to the deck framing. My point is to avoid having the leg separate the surface from its framing, which will destroy the deck platform.

You might also find it wise to get an expert on framing to look at the work. A "well qualified" carpenter can find mistakes that we can not even imagine. A full audience is very near the normal design load of 125lbs/sq-ft.


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## JD (Mar 6, 2015)

10 feet in height happens to be two scaffold frames. Depending on how visible the under-works are, this would be a heck of a lot less weight to move around, and structurally solid. Generally, when we used to use these for follow spot platforms, we took the wiggle out with cross straps.


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## StradivariusBone (Mar 6, 2015)

With platforms that high, I've heard adding a toggle around the legs (in addition to the aforementioned crossbracing) can add stability.


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## lwinters630 (Mar 7, 2015)

When a little platform becomes the second floor of a house with the whole audience oh it.........go with standard home method and code. Single legs with screws will not pass code if AHJ comes by.


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## robartsd (Mar 7, 2015)

lwinters630 said:


> When a little platform becomes the second floor of a house with the whole audience oh it.........go with standard home method and code. Single legs with screws will not pass code if AHJ comes by.


I would go with this with the exception of not necessarily fastening to the floor it sits on. (Providing an alternate means of keeping the bases of the various walls from moving relative to each other.)

StradivariusBone said:


> With platforms that high, I've heard adding a toggle around the legs (in addition to the aforementioned crossbracing) can add stability.


Yes, as compression members get long, they tend to buckle. Provide adequate bracing for your vertical supports. I'm not sure that a 2x4 stud wall is adequate to prevent out of plane buckling at 10' high - 2x6 studs might be required. (I'd block a stud wall to provide in plane bracing to the studs at least every 4' vertically - and sheath an adequate portion of the wall for shear strength.) Again, this should be just like a bearing wall of a house with 10' ceilings.


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## Christopher71188 (Mar 7, 2015)

Yeah if I was going 10' with a full audience I would be a tad bit worried and have someone who knows structures better than I do take a look. We are only getting the pit floor to stage level, so about 3 1/2 feet. thank you all for the info!


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## lwinters630 (Mar 9, 2015)

It is probably worth mentioning here that when an audience is put on stage , it violates the intended use of the area. Certain codes need to be checked and adressed. For example, if the stage edge is elevated, then safety railings are needed. Actors are assumed to have been trained on safety of a stage edge, the general public us not. Egress, isle clearance and emergency lighting also come to mind. 

Last time I had the audience on stage the AHJ almost shut the show down. Fortunately they allowed us to make adjustments to comply.


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## Christopher71188 (Mar 10, 2015)

Yes I have decided to go with the stud wall style legging. I think this will offer the best and most support. Knowing that I do not need to screw it down but can just cross brace will help. I know now to screw into the plywood but only into the legs and frame.

Winters360, I have been in touch so far with our local fire marshal to check and make sure they are happy with what we have. He has looked over my drafting's to check for paths of egress & isles. Both are within (actually greater) than required. I will have to ask about emergency lighting, but it may be covered with the battery operated exit signs I will be hanging. I plan on installing handrail covering the stages edge. I have talked the director out of adding additional risers on top of the extension, so that is at least one battle won!


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