Framing garage ceiling for attic storage

2669 Views 16 Replies 5 Participants Last post by P C D, Jan 28, 2020

AlchemistNow

Discussion Starter · Jan 26, 2020

My wife and I recently purchased a house with a detached garage. I want to he able to use it for storage of our miscellaneous boxes, old baby clothes, etc as well as park each of our cars in. It is a 24' x 24' garage with 24"oc rafters, however only five run horizontally to make the "ceiling". My question is when I frame my 16"oc floor joists, should I attach the few that would land on the five existing 2x4s or leave the existing trusses be and frame only attaching to the top plate of the walls? Or do I need to scrap the roof and reframe the entire thing? (I hope that's not the case)

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Marson

· #2 · Jan 26, 2020

I don't see why you need "floor joists" at 16" oc. I'd just put them at 24" oc, and use 7/16 OSB for "decking". Given the span and the fact that you are using 2x4's, this will only be suitable for light storage no matter what you do.

AlchemistNow

Discussion Starter · #3 · Jan 26, 2020

The little information I've read before coming here to ask for some specifics suggested minimum 2x6's at 16"oc. So not truly floor joists. And the floor will then sit above the five trusses. I was just concerned on the weight of the floor and the storage putting too much stress on the roof framing. The last thing I want is my garage roof collapsing in on our only two vehicles.

AlchemistNow

Discussion Starter · #4 · Jan 26, 2020

I want to be able to install an attic ladder and be able to carry and walk on the decking. So I want it structurally sound.

Nealtw

· #5 · Jan 26, 2020

No body puts up a sign depicting the safe weight on a sad floor.

If you are going to do it do it more right.

The beams over the doors is not big enough to take any more weight so just do the back half.

Put a 2 ply LVL from side to side with jack and king studs.
2x10s on the back wall can be cantilevered over the beam 1/4 the length of the 2x10s.

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Bud9051

· #6 · Jan 26, 2020

Need more pictures to make a guess. I don't see any sign of trusses. With 2x4 bottom chords they were not planning on anything up there. What is supporting the middle of those 24' spans?

Bud

AlchemistNow

Discussion Starter · #7 · Jan 27, 2020

I may be using incorrect terminology by saying trusses, I am merely an electrician not fantastic on carpentry terms.
They are only supported by a 1x6

Are you suggesting an lvl across the center of the garage providing the front edge of the storage space? And then reframing the back wall with 2x10s?

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Nealtw

· #8 · Jan 27, 2020

AlchemistNow said:
I may be using incorrect terminology by saying trusses, I am merely an electrician not fantastic on carpentry terms.
They are only supported by a 1x6

Are you suggesting an lvl across the center of the garage providing the front edge of the storage space? And then reframing the back wall with 2x10s?

No. the floor joists would be 2x10. The back wall should be fine. But would like to see a picture of it.

The 2x4s you have now are called rafter ties, only there to stop the front and back wall from spreading outward, the 1x4s up to the rafters are holding the 2x4s up because they are not strong enough to hold their own weight from sagging .

AlchemistNow

Discussion Starter · #9 · Jan 27, 2020

Gotcha.
So say I took the back 10' and put up an lvl across the width, would I need a support beam to hold the lvl in the center? And are 2x10s necessary or would 2x6s provide sufficient support?

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Nealtw

· #10 · Jan 27, 2020

AlchemistNow said:
Gotcha.
So say I took the back 10' and put up an lvl across the width, would I need a support beam to hold the lvl in the center? And are 2x10s necessary or would 2x6s provide sufficient support?

We build anything that looks like a floor out out of 2x10s. For storage maybe 2x6, but I would go to 2x8 and 24" on center and 5/8 T&G plywood.

I would put the lvls as close as I could to the door tracks and then run the floor a couple feet passed the beam to get the extra deck.

AlchemistNow

Discussion Starter · #11 · Jan 27, 2020

Nealtw said:
AlchemistNow said:

Gotcha.
So say I took the back 10' and put up an lvl across the width, would I need a support beam to hold the lvl in the center? And are 2x10s necessary or would 2x6s provide sufficient support?

Click to expand...

We build anything that looks like a floor out out of 2x10s. For storage maybe 2x6, but I would go to 2x8 and 24" on center and 5/8 T&G plywood.

I would put the lvls as close as I could to the door tracks and then run the floor a couple feet passed the beam to get the extra deck.

Okay, and the 2 ply lvl can span the 24' supported only on the ends? 10" width for the lvl I assume?

Marson

· #12 · Jan 27, 2020

AlchemistNow said:
Gotcha.
So say I took the back 10' and put up an lvl across the width, would I need a support beam to hold the lvl in the center? And are 2x10s necessary or would 2x6s provide sufficient support?

That's a question for an engineer. You could clear span that, but I would think it would take at least several plys of a 16" deep LVL. Maybe more. You could also add a post mid span and get away with smaller LVL's, but you would need to put a footing in your garage floor. 2x6's spanning 10' would probably be OK for light storage.

Seems like a lot of work for some boxes of baby clothes.

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AlchemistNow

Discussion Starter · #13 · Jan 27, 2020

Yeah, well that's exactly why I wanted to ask questions and get as much information as possible before going to the lumber yard and thinking I could just throw anything up and call it good. I might be hauling all our stuff down into our basement and frame up a quick 2x4 floor to keep things off the possibly moist concret floor. I appreciate all of the wisdom you shared!

Nealtw

· #14 · Jan 27, 2020

AlchemistNow said:
Okay, and the 2 ply lvl can span the 24' supported only on the ends? 10" width for the lvl I assume?

The people that sell LVLs can help with the engineering for the beam. Sometimes they go more and sometimes they go taller. You could go small with a center post, but then you have a center post and you need a footing and all that. You could check into steel beam to. If you do steel you want it drilled so you can bolt a flat 2x6 to the top of it.

AlchemistNow

Discussion Starter · #15 · Jan 27, 2020

Nealtw said:
AlchemistNow said:

Okay, and the 2 ply lvl can span the 24' supported only on the ends? 10" width for the lvl I assume?

Click to expand...

The people that sell LVLs can help with the engineering for the beam. Sometimes they go more and sometimes they go taller. You could go small with a center post, but then you have a center post and you need a footing and all that. You could check into steel beam to. If you do steel you want it drilled so you can bolt a flat 2x6 to the top of it.

I will keep all of that in mind and look into it. I'm assuming this project might get bumped out a couple years to save up for the expense this will take. The wife will just have to be happy with basement storage and invest in a dehumidifier fo

Nealtw

· #16 · Jan 27, 2020 (Edited)

AlchemistNow said:
I will keep all of that in mind and look into it. I'm assuming this project might get bumped out a couple years to save up for the expense this will take. The wife will just have to be happy with basement storage and invest in a dehumidifier fo

Several times I have been asked to build a dormer and room over the garage because the floor is already there. Never saw one where the floor could be used as is because people just built whatever as a floor. They do the same thing in houses.
Do you have a man door into this garage.

P C D

· #17 · Jan 28, 2020

Your new joists will span 24 feet unless you also add a beam, and dimension lumber does not come in 24-foot lengths. You would also want to run them across (on top) of your existing 2x4 joists to avoid overloading the garage door headers. The depth of the manufactured joists required to hold a light storage room over that span would be 14" to 16".

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