I have an old two bay garage that's 28'x50', that I would like to convert into a home. One thing I'm trying to figure out is how to do the ceiling. The ceiling is held up by metal joists approximately 12" high. The ceilings are 13' high and I would like to drywall them. I plan on spray foaming the roof prior to installing drywall. The bottom of the joists have a gap where I could run a bolt or toggle type fastener through. What should I use for studding and spacing?

  • spacing would likely be 16" OC. As for what to use for strapping (studs are for walls) it would depend on the spacing between joists.
    – DA01
    Feb 17, 2014 at 23:10
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    Do you have a picture and what exactly do you want to do with the garage? Also are you sure that the framing meets local building codes? (In my area the code for garage and house are very different)
    – DMoore
    Feb 18, 2014 at 0:30
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    what is the spacing of the metal girders? Feb 18, 2014 at 7:09
  • Is there a support beam in the middle? The roof may not be able to support the weight of drywall ceiling. Drywall would add over 2,500lbs to roof.
    – Justin K
    Feb 18, 2014 at 17:41
  • If it was me I would add a suspended ceiling tiles or create a drop ceiling. Supported by ledgers around whole exterior of building and interior walls. You will have to do load calculations to find out what size ceiling joists you need for your spans. 2x6 2x8 2x10. I would drop ceilings in bedrooms and bathrooms to 8'. This will create an attic space, save on heat, allow for much cheaper fiberglass insulation which will probably pay for all the extra lumber needed. I dont know where you live but spray foaming r36 value over 1,500sf will cost many thousands of dollars
    – Justin K
    Feb 18, 2014 at 17:59

1 Answer 1


I'm assuming since this question is over a year old you've probably found the help you need, but i'm here so here's my answer.

The framing should be a consistent 16 inches from center to center of each board, if your rafters don't allow for this sort of layout the MAX i'd suggest would be about 18-20 inches, any more than that and you'll run the risk of the drywall sagging. Make sure to run a perimeter strap all the way around to secure the outside edge of the drywall as well as give a place for any trim or molding to attach to. Another tip I'd suggest is to use a chalk box to line your rafter framing and drive a longer screw through all layers for added security. As for the insulation avenue, spray foaming will do a nice job however there's a lot of risks if done improperly. Inside and outside temps MUST BE over 65 degrees, any colder and the foam WILL NOT CURE properly and off gas indefinitely causing very substantial health risks. If you spray it yourself make sure to rent an outside air respirator and full faced mask, fumes are no joke, they'll beat you up in a hurry, and unfortunately most manufacturers imply on the product that a dust mask and eye wear are sufficient, but its no where close. I'd suggest rock wool, slightly cheaper per square foot, a comparable r value, plus the added bonus of being able to dry out if ever dampened (foam traps moisture)

Save yourself the back ache and rent the drywall lift, most home improvement centers and building supply company have them available you need only ask, the prices are usually very reasonable however if you've ever hung 5/8 rock over head before, even one piece, you'll know the price is very worth it!!

hope this helps and happy building!!

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