room over garage

[gcan]

I have attic space above my garage and had it converted to a playroom by a contractor and had a couple of questions:

The floor was 2x6 and has a load bearing wall on the right side, is a knee wall due to roof slope, and the other side of the floor joist is attached to a 4x10 laninanated beam wich runs the center of the garage below. In order to match the floor height with the other parts of the house the contractor layed a 2x4 flat on top of the 2x6 then 3/4 plywood for the floor?
The floor seems bouncy but the contractor assured me the floor with the 12' span is correct. I wasn't home when this was done but feel they should have sistered the 2x6 with 2x10's. Even with this I'm not sure how the sistered boards should be attached to the laminated beam, maybe with joist hagers.

Bottom line it's done now with carpet,,,,looks good but I'm not confident my contractor did the job correctly or to a safe level. Before you ask no he didn't get a permit...man I learned a lesson with this, said such a small job it wasn't necessary.

I'm not having this contractor back so either I need to fix it or worse case call another contractor and add to my cost. I am an avid DIYer so should be able to fix if necessary I had to hire a contractor due to work commitments and not enough hours in a day.

Suggestions?

 

[6768rogues]

I don't have a code book or span tables at hand, but shooting from the hip I can assure you that a 12' span using 2x6s is not in accordance with code for a floor, unless they are unusually close together. The addition of 2x4s flat way to shim the floor added nearly nothing to the strength, and more likely just put added weight on the substructure. I would expect to see at least one or two sizes larger. It is unlikely that it will fail without a substantial load, but it will deflect and be bouncy. Span tables are calculated depending on the allowable deflection with full design load. Floors are half of what roofs are, because floors are not acceptable if they bounce and nobody cares if a roof is a little bouncy. A 12 foot span in a roof with 2x6s is common, but not for floors.

 

[12gauge]

i just built a 12ft span 2nd floor in my shop using 2x10"s. I also added support beams attaching to the wall to help hold the load of the building. I'm sure your building wasnt designed to hold the additional load of a 2nd floor.

i was told that 2x8" would have been sufficient by most places i talked too. But i wanted it just as sturdy as a house floor.

 

[wmonroe]

I would sister them as 12' is too far of a span for 2x6's in a floor. Joist hangers would work well to attach to the glue lam beam. They make hangers wide enough to hold two 2x's.
Will

 

[gcan]

sounds like I was right that they should have sistered the 2x6's with 2x10's.

As I stated I have a load wall on one side so going on top of that isn't a problem but with the laminated beam on the other side, that the 2x6's attach to the side of can I get double joist hangers and attach the sistered boards to the beam? Would that be strong enough to suffice?

Hard lesson learned on this....now I have to pull the carpet and floor up to do a do over. I would go after the contractor but had nothing in writing and with no permits I feel stuck.

 

[gcan]

sorry wmonroe types faster than me....he answered my question about attaching to the laminated beam.

Than you for the quick responses

 

[gcan]

UPDATE - sorry I just rechecked and the original floor joist are 2x8's and then they attached the 2x4's flat on top to equal the standard floor of 2x10"s. But still it is bouncy,
I guess like 12gauge said it is sufficient but not in my mind what should have been done

 

[Junkman]

Bouncy isn't a way to know if it is safe. You need to have a lumber yard do a load calculation on the floor by giving them all the information. My living room floor joists are 2" x 12" x 18', set at 12" centers. The floor is solid as a rock when you walk on it, but get a kid jumping on the floor, and it will deflect. Part of it is covered with ceramic tiles, and in 25 years, not one tile has ever cracked or come loose, so I know that the floor is sound, but like I said, if you get someone jumping up and down, it will deflect and you can feel it. Guess that is the reason I don't let children into the house!!!

 

[6768rogues]

Typical floor design under full load is to allow one unit of deflection for each 360 units of length. In other words, an inch of deflection for 360 inches (30 feet) of run. Roofs are 1/180, thus more flexible but still able to hold the load.
The flat 2x4s add almost nothing.
You could put a beam under it to cut the span in half, if you have room. Put in a properly sized manufactured wood beam with end posts under the center of the span and you cut the span in half.

 

[NWOhioChevyGuy]

OK, I am reading this thread and while I don't want to highjack it I have a question of the same kind.

I am working on a garage design with a bonus room above and the first material quote I recieved had attic trusses w/ 2x8 bottom chords spaced on 2foot centers, 28' clear span.

Is this adiquate for something that I plan to make into a Family room / bonus room for the kids?

 

[ScottC]

Talk to the truss designer. He can spec "light storage", "heavy storage", "occupancy", etc. trusses based on the intended use.

 

[gcan]

I agree with ScottC just make sure your truss builder knows what you plan to do and they will build accordingly......

ALSO but be sure you check code for the ceiling of the garage. I used 1/4" plywood for the ceiling of my garage and it was turned down on the final inspection. I had to convince our local inspector that the room over the garage was only going to be used for storage before he would sign off. If it is used for a play or family room it has to have a fire rated ceiling in the garage below. I did not know this

 

[jvcobra]

2X8's on 16" centers is ok for a 12' span using 1/360 deflection and 40 lbs/ft live load. I don't think I would rip it up just yet.

 

[6768rogues]

jvcobra, you must have a span table on hand and I did not, thanks. The species and grade can matter, too.

 

[gcan]

it is 2x8"s on 16 inch centers...then has the flat 2x4's on top then 3/4 plywood.

maybe it meets thw span code, like my contractor said, but sure seems bouncy

do I have any options to stiffen the floor without pulling it up?

 

[jvcobra]

6768rogues - yes species of wood does matter, 2 X 8's on a 12' span is good down to #2 Douglas Fir.

I don't expect the 2 X 4's laying down to provide any more significant strength and were just a way to get the floors even. If it were me and this is just a play room I would leave it, a little bounce could be fun.

 

[kbs2244]

RE; cross bracing

Before you tear it out from the top go in the garage below and take off the celing drywall. Then install 2x8 cross bracing at the 4 foot point on the spans. That will give you 2 rows of cross bracing. It should be plenty.
(Cross bracing is pices cut to fit between the joists. You nail through the joist into the end graine of the crosswise peice. Stagger them about 3 inchs so you have room to nail.)
The idea behind cross bracing is that it spreads the load fron one or two joists to the ones next to them. It works with dead loads (funiture) and live loads (jumping kids.)

 

[gcan]

maybe the cross bracing is the answer....this playroom is for the kids and with the air hockey table they tend to jump around a lot so I really would like to find a solution

 

[Kevin54]

Here is a chart on floor joist spans. http://www.ces.ncsu.edu/nreos/wood/ag-603.pdf
I was going to post one out of my Pocket Reference guide but cannot get the pic small enough after I scanned it.

 

[gcan]

thanks for the chart, according yo the chart it should be able to span 12'10" at 40PSF.
With the room being 12'-8" it appears it just does meet code, as the contractor said.
I wish he would have shared this with me during the process, I'm a big believer in overkill and would have told him to beef it up especially having 12 year old girls up there doing cart wheels.

thanks again

 

[kbs2244]

Don't forget to re-drywall after it is done.
Fire code want's drywall on all surfaces of an attached garage.