Platforms for Heavy Load Bearing

[theILLUMINATEDfrog]

Just to settle up front, No I can't contract out, Yes it has to be built by us, and No, I can't change the amount of weight it has to support.

With that cleared up, here's what I've been charged with:

To build two platforms 30" tall, faced, with stairs on both sides. Basic Design, Check.

...the kicker... one platform must hold a grand piano (yes, 11'x4' and approx. 1100 lbs.) + musician + Stool, etc. ... the other will bear a load closer to 500 pounds.

I've helped build plenty of sets and my WOOD carpentry skills are good-- what I'm lacking is technical direction. I know hardware, etc. but need some advice on whether or not to use Steel legs, etc. The weight load is making me a little apprehensive. Suggestions?

This is to be a modular, unit-set(esque)-- No set changes- will stay in place for approx. 2 months but then must be stored in individual modules (stairs, 1/2 platforms, etc)

[kicknargel]

I think you'll be fine with wood--just beef it up a little. You may consider using two layers of 3/4" plywood (I'd steer clear of OSB, etc) since the piano's weight is concentrated on three small points. Maybe a 2x6 frame, glued and screwed, with no more than a 2'x4' space. Importantly, I'd do type of compression leg--either the "studwall" style (build a studwall and attach the platform on top) or double up 2x4s so that one goes from the floor to the bottom of the frame and the other extends up inside the frame and bolts to it. Legs no more than 4' spacing--maybe reduce that, too. Cross brace well.

But really, a piano is not much more load than several people dancing (because their load is dynamic) so standard, good construction technique should work. I think the biggest difference is the concentration of the weight on those three wheels.

[Van]

There are several issues to consider when building with these kinds of loads. While I appreciate and agree, <somewhat> with Kicknargels assesment that good standard construction processe apply I'd caution you against being being at all lax in your apporoach.

1. 2 layers 3/4" CDX or better for a top to the "platform" minimum! The two layers need to be layed at 90 degrees to each other. Nailed / screwed every 12" in the feild 6" on the perimeter.

2. Framing should be of 2"x6" stud grade or better minimum. I suggest using Simpsons around the exterior rim joists do not rely on screwing / nailling alone.
Joists should be on 18" centers maximum.

3. Support framing. If you are going to build 2x4 knee walls then I suggest building them with 16" centers. 2x6 walls you can get away with 18" centers. These knee walls need to be placed every 24 " along the length of your joists and while they can be "toed-in" this is another great place for a Simpson.
Once the knee walls are installed you must install X bracing between the individual knee walls for while the load is mostly going to be static the potential exists for huge dynamic sheer forces. The cross bracing should be of 1x4x8 and should be tied <nailed> to every stud it crosses.

Important notes on these specifications.
Do not ignore the importance of screwing / nailing the field of the flooring. You are not merely tying the floor onto the joists you are, in essence, building a triscuit - style stability into this floor covering. the more points of tie-in the less force on each individual point. If there is anything you don't understand in this please don't hesitate to ask more questions.

[scenerymaker]

Another thing to consider. Is it possible to lay out your joists such that they land directly under the piano wheels, spreading those point loads out even more?

[jwl868]

Take the time to draft the project to scale ahead of time.

Also, I thought the leg spacing of a grand piano was greater than 4 feet.


Joe

[Tex]

Listen to Van.
Knee walls and joist hangers. Build it like a house.

[theILLUMINATEDfrog]

Thanks guys. My load in isn't until November 1st, so I'm sure I'll be checking back in the next few weeks as we begin to build. This is a great start on the tech drawings.

[Chris Chapman]

How are you going to get the Piano "up" onto the platform?

[theILLUMINATEDfrog]

Well honestly, that's still up for discussion too. Our thought was a really long inclined plane. Better Suggestions?

Don't you love directors that dream up these things and then say "Ok, now find out how to do it!"

[theILLUMINATEDfrog]

And yes JWL, its quite possible that the legs are more than 4' apart--- the 11' is pretty right on, the width was just an estimate. We're within the first 24 hours of hearing about this build, so not many specifics have been nailed down yet.