Interior, Free Standing Platform

MrLinux

Not sure how to phrase this.... I don't think that this is a standard building
question...

I have a home office room that is 18x12 with a 12' ceiling. It is built on a
slab foundation.

In order to take advantage of the high ceiling, I would like to build a free
standing platform on one end of the room that is 6 feet deep that spans the
width ( 12' ) of the room. It would be 5.5' high and be open along the front
so that I could use the bottom part for a storage area and the top of the
platform would be used as my office space. It would need to support some a
good amount of weight (me, office furniture, computer, etc ) so it probably
needs to support ( guess ) 3K pounds.

I don't want to have to do any foundation work.

I know that it would probably make more sense to put the storage on
top and leave the office on the bottom... but I like that idea of being up
in the air...

I know that with the top of the platform being 5.5' up, that leaves me with
6.5' of walking area up top... might need to lower the platform to 5'... I
might also want to make the platform 7' deep instead of 6' to give it a bit
more space.

Is there some way I can build a platform that will work?

I was thinking that if I put up a cider block wall along the back and sides
( 12' x 6' x 5' high ) and put a 12' steel I beam across the front, I could
put 6' floor joist that sit on / in the cinder block wall and I beam and put
plywood decking on top of the floor joist. If needed... I could have a support
in the middle of the I beam that helps support it.

Is this an 'insane' idea ( my wife's words IF I tell her about it ) or could
it possibly work?

Also... what kind of building codes am I going to be up against?

Thanks - jack

Tscarborough

It is called a "freestory", and shouldn't be hard to do. Think of it as a deck inside your house and you will have the right idea.

NateHanson

I'd think you could skip the concrete blocks and steel I beams. Just frame the floor with joists running 12', put that on framed walls on either side, attached to the actual walls, or use posts and beams like a deck.

I like your storage-below idea. I assume you're going to put drawers/file cabinets and that sort of thing down there. It's not going to be a very accessible space for other stuff because you'll end up with about 4' of height below your platform. Personally I'd keep 7' of head room, because 6.5 would make me feel claustrophobic.

Maybe you should wrap the workspace in one-way glass, so you can look down on the room like some sort of manager. :p

MrLinux

ok... ... so assume I do a short wall on the ends using 2xX studs and I
span this with 2xY's on Z" centers and I want to support W pounds...
what should X, Y and Z be to support W? If W is 3K pounds... what
are X, Y and Z? Is there an easy ( cheap ) way to get this answer?
How do I come up with a good guess for W?

I'm just worried ( I've never looked at doing anything like this before )
that the ends / short walls will have too much load on them and put too
much downward force on the concrete slab. The reason I said use the
cinder block wall along the back was just to spread the load....

Lastly... if I use two short walls on the ends with the floor joist spanning
them... I can always ( slowly ) jack up the floor and adjust the height of
the side walls. Try it out with a 6' walk space up top for a few weeks and
lower it 6" if it's too claustrophobic... The more space up top... the less
space down below... this assumes that I can just use some short walls
on the side to support this structure.

Here is a thread
High Ceiling utilization
that I can use to talk about the interior design aspect of this if anyone
wants too...

jack

MrLinux

bump...

I am ready to start building my platform.... the only thing I know for sure
is that it's going to be 6x12. I'm going to put some 3/4" maple hardwood
on top of some 3/4" tongue and groove plywood....

I'd like to use 2x4 material for the framing. I only have a 12' ceiling so
the thickness of the platform will reduce headroom from the work area
or the storage area. I can use 2x6 if it reduces the wood or overall weight.

I don't want to over engineer this but I don't want the floor to be too
bouncy or sag over time. This is going to be used for my computer work
area for the next 20 years....

If I am going over a 12' span and I have 1.5" of flooring for my walk
area...

How wide do I need to space my floor joist?

Do I want to use double joist and lag bolt them together to make them
stiffer or will single joist suffice. I will use double joist on the outside
edges so that I will have a good base for the edges of the flooring.

I am planing on putting this up about 12" and testing it out for a few
months. Once I decide that it's going to be stable and a large enough
area for my office needs, I'll jack it up to the 5' level or so... and build
some 2x8 knee walls on the ends.

Any info / ideas / suggestions would be appreciated.

jack

Kingfisher

use 2x8 spaced 16" will meet code but I would use 2x6 spaced 16" and build a knee wall under the middle breaking the true span to 6" this is for suthern yellow pine #2. I would not worry about a foundation under the knee walls and would place knee walls under the ends if you can't get a ledger board connected directly to the wall studs. Good Luck

kgphoto

Don't forget the guard rail. Even falling 5 feet can kill you.