8' High 4' by 16' platform

[Devon]

Hello!
I found a similar thread, and am looking for some more information.
I need to build an 8' high platform that runs 4' by 16' using 2 stock 4' by 8' platforms. There are other platforms for the show, heights of 2', 4' and 5'. I have already built this, using 4x4s as legs, and 1x4s as cross bracers. Now I'm on to the big one! I cannot attach anything into the deck. I was thinking of (somehow...ideas?) attaching the legs to the tops of 2 other 4x8 platforms, having the legs be sandwiched between the platforms (in case this is confusing: 2 platforms on the deck, legs attached to the tops of them, then 2 more platforms 8' high). Are 4x4s the best legging option? I've been reading a lot about hog troughs... I definitely need it to withstand weight.

Thanks in advance for your help and advice!

 

[danTt]

Do you have a drawing of the relative location of these platforms to each other? A picture would be much more helpful when considering cross bracing.

 

[Devon]

Regarding a drawing: I can't seem to get anything to work- pictures won't copy/paste; attachments won't upload. I apologize, and I'll try to explain it. GRR!

The 8' high platform runs the width of the stage, upstage. Coming out diagonally from its DSL corner is the 5' high 4x4 platform (connected via stairs). Coming of the upstage's DSR corner is the 4' high 4x4, and directly downstage of that is the short 2' high 4x6.

I know it's not as good as a picture; I'll keep trying.

 

[derekleffew]

Perhaps this will help in the posting of pictures: Posting pictures/videos/files on ControlBooth - ControlBooth .

In my opinion, 4x4s are [-]never[/-] seldom the right answer for platform legs. Either single 2x4s or 1x4s at 90° (whaler, hog trough) are plenty sturdy, the key is the cross-bracing. Since legging up an 8' high 4' deep x16' wide assembly is rather difficult, I'd probably build an ~7'-7 3/4" high knee wall, and put your stock platforms on top. See http://www.controlbooth.com/forums/scenery-props-rigging/5191-my-platform-system.html . I'm old fashioned, but I like 3/8" carriage bolts. I DON'T like drywall screws. There's going to be some sort of railing on the upstage side of this 8' platform, right? And no rise on the stairs greater than 8", with riser+tread= ~17", right?

 

[Van]

I think Derek has the right of it. Hog trough legs in the corners and atleast one in the center, then 1x cross bracing should do the trick nicely. If you wanted to build a 1x4 stud wall with studs @24" centers that would work as well. I second Dereks advice of Carriage bolting Hog Trough or whatever kind of leg you do use.

 

[Tex]

My vote is for the stud or knee walls. Anything over 4 feet tall gets stud walls these days. It may be overkill, but I can sleep at night and not dream about falling kids.
I don't use drywall screws anymore either. I've switched to the GripRite wood screws with Torx heads. They're rated for construction (unlike drywall screws) and the Torx drive makes them MUCH easier to put in without stripping the head of the screw or the bit. My freshman girls now have no problems driving three inch screws.
When I do use legs, they get carriage bolts. Period.

 

[jglodeklights]

I agree with all that has been said, especially working at the height you will be. ALL platforms should eventually be bolted together, IMO. My theater's set for Titus Andronicus was essentially an iceberg rectangle at 8 foot high. Structure was the stud walls with 2 foot spacing, Stressed Skin/Triscuit platforms atop, and several cross bracing elements. That was quite solid. The most shimmy was along the long direction (20 feet), which had less cross bracing, due to storage space needs (yuck, had a genie under it) and actor entrances, and due to platform construction had no bolting between platforms. Especially at this height, I also don't like drywall screws (or lower end wood screws). They aren't shear rated. Depending on your action and where you attach to, 50% or more of the stress you generate and transfer to your attachment points could occur in a manner putting the force laterally on your attachment hardware, which is shear force. It is pushing on the hardware in its thin direction. They also are made of metal that is generally more brittle than that used in rated hardware. Yes, construction nails can bend relatively easily, but you'll notice it can take quite a bit before they break. This is because they are rated against shearing. Screws bend easily, and break extremely easily. Nails, and especially bolts, resist this.