Room over garage floor joists?

[rmanrman]

I have a oversized one car garage attached to side of home
When Home second floor was framed it was extended above garage also with full 8 foot ceiling and stick built framing. Here’s the question the second floor floor joists are sistered 2x6 x12 feet to center of garage with a triple 2x8 support then another 2x6x12 sistered to back of garage top plate. The floor is 3/4 osb t&g
Now 5 Years later I’d like to build a man cave in this attic space but not sure if I have a strong enough floor? Btw the 2x6x12 are 16inches on center
There is a full attic of stuff and the 5/8 drywall ceiling has no cracks in the garage ceiling. No real heavy items intended for man cave room No masonry fireplace or hardwood floors or slate pool table. Just couch large tv. Foosball table and small frig and bar. There is a full walk up steps with fire rated door in garage to get upstairs so finish work and use will be easy. Any thoughts if I’m ok with the floor framing? Also the 2x6x12,s were the rafters from the original one story garage glued and nailed together on 16 in center. Contractor said ok but too cheap to add larger floor joists. Thanks

 

[CombatNinja]

What type of wood is it? Any time I see 2 x 6 for a floor, I am leery. How far does that tripled 2 x 8 span?

 

[mcbane]

What is the spam of the triple 2x8?


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[Homerr]

Can you post a sketch of the plan showing the joist directions and some dimensions? A picture or two as well?

I think I understand the layout but want to confirm a few things -

What is the span of the (3)2x8?
Do you know the species of wood used for the framing?
Is the roof 100% supported on the outer walls?
What is bearing on the garage door header?
What part of the country are you in?

 

[Bretny]

2x6 running 12ft is about half the size they should be. Doubling up 2x6 dosnt make them a 2x12.

 

[firebirdparts]

You don't need a 2 by 12. Don't go nuts and give bad advice.

For the joists, a 12 foot span, and the typical 10/40 psf dead/live load, you require 2 x 8's on 16" centers if the wood was yellow pine or douglas fir. Sistered 2x6 is an odd way to go but maybe acceptable if I understand what you really mean.

Let's wait and see what the span is on the beam.

 

[CombatNinja]

He said it spans a single garage so I am thinking 12-14 feet range. Where is the OP? He probably fell through his weak floor joists and is in the hospital

 

[Homerr]

He said it spans a single garage so I am thinking 12-14 feet range. Where is the OP? He probably fell through his weak floor joists and is in the hospital

This is very possible, except it's probably the (3)2x8 that are failing.

If this garage is 12'x24' with the (3)2x8 bisecting the long dimension (2x8's are 12' long) then the joists are barely making it if they are DF#2 or better. HF and SP #2 both fail by around 15%.

However, the (3)2x8 beam supporting these joists fail much more spectacularly, by 250-300%.

This is why you have an engineer, or even a lumber yard, run some calcs instead of eyeballing it in the field.