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I have a garage that is 22 feet by 18 feet. It does not have a ceiling but it has a roof and everything. One side is the wall that it shared with the house. And the other side is the outside wall. I intend to screw in a 22 feet 2x4 stud to the side walls. Then use 18 feet long 2x4 studs across resting them on top of the 22 feet long studs on the walls. I will then screw them in. I add the 18 feet studs every 16 inches all the way to the end. Finally I like to add drywall to the bottom of the 18 feet studs to have a drywall ceiling. Is this okay and safe. Thanksenter image description here

  • Are you asking if this is structurally sound, or are you asking if it meets your local building codes? I don't know where you live, so I can't answer that. I also don't know what kinds of stresses your garage will have to deal with, so I'm not so certain about the other question, either. – Ryan Budney Jul 10 '18 at 22:26
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2x4’s at 16” o.c. spanning 18’ will not work. They’ll sag under their own weight, much less adding a layer of gypsum board.

The Code requires a minimum live load of 10 lbs. per square foot for limited storage (maximum clear space between new floor joists and roof joists of 42”) and 20 lbs. for uninhabitable storage space. (See IRC Table R301.5.)

If you want to use 2x4’s, I’d add a mid-span support, like a 2x4 extending from the 2x4’s up to the roof joists. If the roof joists don’t align with the 2x4’s below, you can add a 2x4 strongback the length of the garage. This will give you an allowable live load of about 24 lbs. per square foot and a dead load of about 4 lbs. per square foot, (joists at 16” o.c. and gypsum board on bottom),depending on the species and grade.

If you don’t want to use a mid-span brace, you could use 2x8’s at 24” o.c.

(BTW, your drawing shows 16” BETWEEN joists and it should be ON CENTER. Oh, and the first joist from the wall should be 16” o.c. From face of wall to its center.)

  • Thank you for the feedback. Another question is that if it is OK to screw in Drywall to the roof rafters. In the Garage looking up, you can see the 2x4s that are about 12 to 14 inches apart. Can I screw in some Drywall to hide the 2X4s. I live in California. Thanks – Bobby Jul 12 '18 at 22:29
  • @Bobby Yes you can add drywall on the bottom of the roof joists. If you have insulation between those joists, you will want to make sure you have 1” of air space between the top of the insulation and the bottom of the roof deck. Also, you will need to add a vapor barrier on the bottom of the roof joists, because it sounds like the garage can get hot and may have moisture that you need to keep out of that enclosed space. Make sure you have attic vents too. – Lee Sam Jul 13 '18 at 0:24
  • You'll need to use 5/8 sheetrock, too, due to the fire code. And the sheetrock must be taped and mudded, at a minimum, even if it is not finished. Again fire code. – CBass Jul 13 '18 at 4:21

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