Reduce the thickness of framing.

[ssharma8]

Hi,
I need to build a small walk in chamber for an experiment of mine. Initially I was using 2x6 wood joists for the roof and the floor. But due to height constraints of the lab in which the chamber has to be built, I have to reduce the height of my chamber while still letting it be a walk-in.
The chamber has to be internally lined with wedges (anechoic) which are 13.5" in depth and about 5lbs/ft. Is there any way to frame the roof and the floor such that the thickness of the roof/floor framing is not more than 2" but is strong enough? I calculated with putting the 2x4 studs on the roof with the 2 dimension heightwise, it gave me a deflection of 0.5".
The chamber is 3.2m in width and 3.5 in length.
Please do give your suggestions.
Thanks in advance
Shweta

[Richard A Hetzel]

This chamber is going into an existing space, right? I don't understand the term "roof/floor" framing. I don't know if the wedges weight 5 pounds per foot, or five pounds per square foot. Are you using the lab floor for the chamber floor? Does the roof have to carry the weight of the wedges? The floor also? Why not use 1/2 inch plywood for the floor, giving you an extra 1 1/2 inches for the roof thickness, which will allow you to place the 2x4's the right way? They should be able to span roughly 10 feet and support a 5 PSF load.

[ssharma8]

Hey
Thanks Richard for replying.
By roof/floor framing I mean framing for both, the roof and the floor. The chamber is going into an existing space but we cannot use the lab floor as the chamber floor since we have to vibrationally dampen the chamber, will use spring mounts for that. And since the floor will also have to support weight of atleast two people at a time, through floor gratings, I dont think using plywood is a good option.
Is there any other way I can save of space?
Thanks
Shweta
The wedges weigh 5lbs/sq ft, sorry for the error before. The wedges will cover all the walls, floor and the roof.

[Richard A Hetzel]

So, you have a total of four inches available total, for both floor and roof. How do the wedges attach to the surfaces? Do you need to nail them, or are they glued on? You might consider 2-inch tongue-and-groove roof decking material. Usually, with snow loads, it can span about 6 feet. With your loadings, it can do better, and will probably be adequate. I think it's available in Douglas Fir, which is quite strong.