Expert: Roger Zona - 11/2/2011

Question
i live on a third level of a rental apartment complex in scottsdale az. i built a small music recording room in my second bedroom to keep the noise level down and away from neighbors.   i used i piece of 3/4thick 6'x8' plywood for the bottom and used total of 8 pieces of 3/4'' 4x8 drywall and 6 pieces of 1/2'' 4x8 for the exterior and 6 pieces of 1/4'' thick plywood for the interior of this mini room in side the bedroom. for the interior i used 2x2s to support them and used 1/4 plywood for the interior.  each drywall and plywood inside   was covered with 1/8'' thick & 1lb density mass loaded vinyl to make the walls sound proof. the base plywood has 18 heavy duty casters to move the whole structure if needed, though it became heavy after i placed all the studio gear in it. now it sits on the very corner of the room right next to patio wall and the wall facing the neighboring apartment. the bedroom where this portable room sits has a bathroom and a walk in closet inside of it also... the dimensions of the finished music booth room is 7'x7'x8' and from my calculations weight of this whole thing is about 1000 lbs including the equipment inside. since the weight is distributed on a 8'x6' area thru  casters i'm thinking it should not create any problems that support the floor or am i wrong? the apartment complex was built in early 90s and has wood floor construction except the patio and outside walking spaces and the stairs are made of concrete.  from my research 40psf live and 20psf for dead load are the only limits that i could find as building code, though i don't know how to translate those codes to my situation; would my music booth cause  any potential floor support problem with this weight on a third level rental apartment?

Answer
Hello Steve,
From your description, I suspect you are somewhat in an "over-kill" mode.  I own a warehouse complex and have some rock band tenants.  I require that they install (or I do at an agreed upon rate) sound absorbing material.  I have found that the best product is the foam acoustic panels.  These have a dimpled effect that increases the absorption factor.

The weight distribution factor (40psf live and 20psf dead) is good.  More commonly a live load of 30psf and a dead load of 10psf is used.  However, the building code in your area could require the limits you noted.  Did you check with your building department to see if they have any minimums?  Usually the building architect hires a structural engineer to determine the floor construction and loads.  Perhaps your landlord would have that information.

A distribution area of 48 sq. ft is sufficient to carry 1,440 total weight with a live load of 30psf.  If your figures are correct (40psf) your floor will support 1,920 lbs.  The dead load is the sum of the floor assembly - joists, subfloor, finish flooring and ceiling below.  The size and spacing of your wood joists and the species of wood would determine the load capacities.  If your floor system is steel bar joists or concrete slab, the building code will determine the maximum loads allowable and the material is designed to meet those requirements.

I hope this has been helpful.

Roger
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