Stage Floor Sleepers

Hello CB Folks,

I am writing to express my curiosity about the recent decision made by my school to replace the stage floor. The 1/2 inch sheets of plywood that were originally installed have delaminated and compromised the integrity of the stage. The current floor makeup consists of an elevated concrete pad, a vapor barrier, 2x4 sleepers on 16" centers, two staggered 1/2 inch sheets of ply, and a masonite top. There are currently no neoprene pads within the system.

The school wants to replace the existing stage with a stage that has the exact same specifications. However, I have advised them to consider upgrading to a minimum of the same makeup but with 3/4 inch sheets instead of 1/2 inch and with 12" centers. While this would improve the quality of the floor, it creates a logistical issue of transfer from the stage to the hallway as the height increases by half an inch.

Most of the quotes received for this project have suggested grading the space to create a ramp onto the stage. However, I have received one bid that proposes replacing the 2x4 sleepers with 1x4 sleepers to account for the height differential. Ignoring the fact that the math is short, I am concerned about the impact of downgrading the dimensions of the sleepers. My assumption is that this would significantly reduce the floor capacity to take on substantial weight. Am I right, or am I thinking about this the wrong way?

Thank you.
 
Woven 1x4 sleepers could be workable to give you a little spring but you would want to have deflection blocks with a small air gap (like 1/8" between the blocks and the slab) so that for any concentrated loads, the floor system "maxes out" and the deflection blocks take the force of the load directly into the slab. Under footfall, the floor still has some cushion -- under heavy concentrated loads, the deflection blocks contact the slab and do the heavy lifting -- though under this approach, it's important to make sure your slab is actually flat and level, and you may need to grind down and high spots otherwise the deflection blocks will just ride on any high spots in the slab constantly and the could give you "dead spots" in the floor.

As for a non-sprung configuration, whether the sleepers (assuming they are laid down on their sides -- not upwards like joists) are 2x or 1x has little to no effect on the capacity of the floor. In either case, the load is being transmitted through the floor paneling, through the 3.5" dimension, and down into the slab.

Without running the math, I can't speak to the centers between 1x4's. I can say though that without any neoprene or woven sleepers to provide some spring action, simply decreasing the spacing between sleepers and increasing the thickness of the ply layers will make the floor more rigid and less suitable for dance. It may only be marginally more rigid than what you have now and that may be acceptable to you -- but it will be more rigid.

Full disclosure: Stage floors can be quite complicated between "use no adhesives", which paint you lay down, grades of sheet products, attachment methods, so on -- so to be clear, this not comprehensive guidance on how to build a stage floor -- and you probably don't need to both increase the density of the sleepers and increase the thickness of the plywood. The two factors are related in how much capacity the floor can handle, but with whatever you do, you do need to meet minimum 150PSF capacity required by building code for stage floors.
 

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