Let's suppose that you want to build a platform up about 7'. It will be about 14' wide on the back end and 10' the front end, 4' front to back. It will only be supported on the 14' side and on the ends (tapered in at 60 degrees). The 10' side will be an open span, This is for a theater set. and there will be three adults on the top.

The set manager wants to do one 2x10 across the open front (10') and another across the back. Then run 2x6s across from the front to the back 2x10s. Will that be strong enough, or would it be better to run 3 or 4 2x10s the long way? The back joist will be supported by a wall (I think)

Just thinking out loud but I’d be concerned if the weight of the platform/actors cantilever could be supported by attaching to a wall without any supports

12 hours ago, kmealy said:

The back joist will be supported by a wall (I think)

THAT statement alone scares the crap out of me.

I would think that available and planned supports would be priority when supporting a 3 person DYNAMIC load.

3 adults is what? (300 to 800 #'s cantilevered out from the back wall) and they (the people) won't just be stationary.

I'd rethink the whole thing and/or make sure the insurance is paid up.

just my 2 cents. I am NOT a engineer.

I have seen masons on scaffolding working on 2x12s supported on 8 ft. centers BUT that is certified walkway planking, and masons are not noted for being careful