Platform height considerations

[Doug Lowthian]

Director wants a two level set, Ability to walk under the second level (so min maybe 6 feet), second level a sort of non-cantilevered balcony with stairs onstage and escape stairs to back stage. Plan on OSHA compliant railings through out.

I used 4x4 Yale triscuit/stud wall system last platform i made which was 4 feet tall .

Question: Given a 6 foot high platform and no ability to secure to the floor, how wide/deep would you make it to be stable?

Thanks in advance...

 

[microstar]

You can make a 6' high 4x8 platform stable by simply cross-bracing legs properly. If you have stairs attached, that will increase stability a lot.

 

[BillConnerFASTC]

The cantilever will require a little more thought. You can't anchor to the floor but could you get some weighty items - BIG sand bags or plenty of small ones, a Jersey barrier, a barrel of water - to tie down the back end?

microstar is right about the stairs but just a 4 x 8 at 6' high and several actors rushing to and/or leaning off the long side? Not real certain it would not tip. I'd be more comfortable at 6 x 6 minimum. Of course some outriggers would help too.

Cantilever - probably wants at least 3 times not cantilevered to cantilevered - so a 3' cantilever is a 12' deep platform. Yes you can do it with less, but not easy if not anchored.

A long time ago I asked a manufacturer's designer of orchestra shells how he calculated how much counterweight in the tower base to prevent tip over - like when moving it and it hits a bump. He wasn't sure how it was calculated but he knew when it was not enough by going into shop and lifting the back end and if he couldn't tip it, apparently it was enough.

And I usually think 8' floor to floor if you have to walk under. Really should be 6'-8" clear so with 6+" of frame, 7'-4" at least?

 

[Van]

How big? The foot print has a lot to do with how stable the unit will be and the amount of bracing needed. And as Bill pointed out. even if you can't go into the floor, the addition of weight to the base can do wonders.

 

[BSchend]

I think some got caught up with seeing the word "cantilever" in your post and ignored the "non" part. (I almost did myself). So I assume you want, in simplest terms, a platform with four legs that's tall enough to walk under? Just one single platform? Anything else to attach to besides the two sets of stairs?

You could do a single 4x8 platform, but it won't be rock solid. I second Bill's dimensions that you should be aiming for a min of about 7'4 with a 6" frame for the platform. You could go normal 2x4, but that leaves very little attachment area for the legs. A 2x6 leg into a 2x6 frame might flex a little, but not nearly as much as into a 2x4.

The cross bracing becomes the hard part if you want the area underneath completely walkable. Ideally you want 2 adjacent sides cross braced. If you need to keep all four sides open as possible my suggestion would be to use 3/4 ply to create corner blocks (just like making a flat) that cross from the legs to the frame. You could possibly cut it in an arc shape for aesthetics and/or to maximize head room. I've used a full 8' long piece that extended the entire platform and 4' down the legs and it works really well.

While you could get away with 4x8, I'd suggest doing 5x8 or 6x8, especially if you have multiple actors up there at once. Even with railings, being comfortable with your head 12-13 feet above the ground is easier with a bit more space to move. It also widens your footprint and makes the unit more stable from tipping (since you can't anchor to the floor). Just note the bigger you go, the more you should increase the size of the 3/4 corner blocks.

 

[BillConnerFASTC]

Oops - I missed the "non-" cantilever also. Mea culpa.

Its sometimes easier to make more platform and brace that - like an 8 x 8, and ds 4 x 8 is just two legs and attached to upstage platform - that is well braced. So many options depending on what you have - space, materials, time, stock pieces, and so on.