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Decoupled floor on wood joist , mass distribution
Old 7th February 2020
Here for the gear
Decoupled floor on wood joist , mass distribution

Hi gearslutz users.

I'm building a homestudio in a room on the second floor of an old house. I have removed everything on the floor to access to the wood joist and estimate the possible load.

The structural ingeneer told me that I can put around 75 kg per square meter of permanent load. The ceiling of my neighbor on the first floor has a density of 40 kg/m² that is fixed to the wood joist (he has another ceiling with drywall + minerall wool), I have a question about the distribution of the load for my floor.

I plan to build a decoupled floor that sits on springs system (resonate freq of 10hz), I would like to know what is the best option to load my deck:

1) put some sand and fiberglass between the joist and the exact equal mass on top of my spring system floor.

2) fill the gap between joist with fiberglass and put all the load on the spring system floor.

I found a super heavy material that has the exact same permissible load that I can put on my floor. This is more expansive than a deck with double MDF leaf and greenglue but if I consider the sand and the time / effort to do it I think that it can be a good option.

I would like to know your opinion about those 2 options, are they equal in terme of insulation performance ?
Old 8th February 2020
Northward's Avatar
You can't successfully float over wood joists that way as the wood joists are often too compliant, which means they deflect with the springs under dynamic load, shoving the f(n) way high and are causing residual oscillation.

First you need to stiffen substantially the existing structure, then float a heavy and very stiff floor over a very soft spring. And mind the potential double spring effect.

It is a very complicated thing to calculate. You will need to use FEM.

Or you can use a soft but heavy floor, and the maths get even more difficult and require very precise load allocation in the room.
Old 12th February 2020
Here for the gear
Hi thanks for the answer, I'm looking for someone to hire that can assist me to calculate those load / frequency.

Any help or contact will be appreciated.
Old 12th February 2020
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