You'll end up with a better job if you use 1/2". What looks straight now probably isn't as straight as it looks. All the butt joints will have a nice little hump.

Your house, though, so it's up to you.

Full sheets of 1/4" drywall is difficult to handle by one person. Stuff is so thin it will break and crack if not handled with care. You'll still have to deal with covering the joints.

So when I did my basement I used 1/2 4x12 horizontally (20' walls). Bumps at but joints? No. I lightly pounded the ends just a little and had to take my time and do extra mud wider and wider until it had a smooth look. A whole lot easier to do it without a helper.

Thought I'd update this with pictures. I've taken out all the wood paneling, that was NOT fun. Some of it was nailed, some of it was "staked" to the wall with nails long enough to trigger a TSA colorectal search. It's all gone now... Ugly stained drywall only now... pretty flat I must say...

It's all dry, the stains on the paper (facing me, that's backwards right??? other side was clean plaster) must predate the new roof, it's an old house...
From what you see, are we still OK to proceed with a second layer, in normal thickness then ?

On the side that is taller than 8 feet (to the roof), any chance I can roll paint on the paper side, with killz or something that at least makes it whiter ? Too high and too many ugly beams to do a good job going all the way up, and frankly I don't care. I just want white walls to 8ft.. This is not the Sistine Chapel !

Bare studs, + drywall, + wood paneling. We got ugly in all kind of styles !
http://forums.pelicanparts.com/uploa...1457915357.jpg

Trash !
http://forums.pelicanparts.com/uploa...1457915405.jpg

Wood removed
http://forums.pelicanparts.com/uploa...1457915427.jpg

Other side, one hole, I did that in a moment of impatience dealing with a cluster of stakes that would not come off...
http://forums.pelicanparts.com/uploa...1457915448.jpg

even uglier higher
http://forums.pelicanparts.com/uploa...1457915488.jpg

I worked with a female painter who kicked butt on the paint at least.
Did everything herself.
She cut all the sheets in half at the store to fit in the vehicle.
Probably a head shake from the pros, but with the ends screwed into 1x6s it made for a solid joint to start mudding on

It would seem that I'm an idiot. Well, maybe that's strong, I'm not an experienced drywaller...
I assumed the thing was on backwards because it's dark brown on the side facing me and the other side seemed like plaster. Turns out the brown side is simply old faded white paper that turned brown. The backside has the thicker paper, but it peeled clean off the few parts that I cut or broke, so I never saw it and assumed it was on backwards!!! So it's ugly but serviceable drywall... I just need to retape, refinish and patch some holes I made (inevitably when pulling 2" nails with a prybar for leverage), mud, sand and paint !! possibly a strong primer first... So glad I did not go at it like a complete berserker and did minimal damage while ripping out the wood panels !!! I still need some sheetrock but like 3 sheets total, not the entire garage !!! Whoopie !!! That, a little racedeck and some more LEDs and I got myself a somewhat less embarrassing garage !

If yer in any doubt about mold, spray the crap out of every square inch with a 10% bleach solution from a garden sprayer.
(Mask and a cross-breeze of course.)
Be generous.
Button up and wait a week.

Then apply Zinsser or other shellac-based primer.
Thinned down or straight. Roll or spray. Cover everything.
Use a 3/4"roller on an extension and do half a wall with one bucket dip. 15 minutes tops.

There are also "encapsulating" products made from sea shells from lowes.
Dries hard as a rock.
I used this on the back of joists/plywood before the insulation and drywall.

Aluminum paint works for encapsulating.

Good idea cleaning up any mold. It might be simpler to just cover the existing drywall with new instead of doing a ton of patches. Use some lightweight or thin drywall since its going over existing.

Since I am a general contractor, let me give the contrary opinion. In the time you have been wondering about this latest revelation, and in less time than you'll spend trying to rehab the old crap and make it look decent, my guys would have yanked the old sheetrock off the wall and replaced it with new sheetrock.

The way I figure it, sheetrock is cheap and mudding and taping new sheetrock goes much faster than fixing old, poorly hung sheetrock. Not only that, but you can make it look better than it does now.

I know it's a garage and you live in California where many people don't finish their garage walls at all but I'd do it right and I'd do it once and be done with it. That includes the "difficult bits" up high, which are essentially no big deal in a drywaller's world.

JR

That was my initial instinct... Then I found that drywall underneath and figured patching would be easier for me (working alone) and not require emptying the garage completely (cars, tools, bench, boxes). Paying someone, for sure a redo would be best. I have no idea what kind of bill that would be, I'll shop around... I spent a couple hours just repairing one sheet (total, not 2 hrs in a row - patching a gazilion holes, patching with sheetrock where broken, second coat of mud, sanding, priming) so you may be right ! I could have hung a new one in the same amount of time !

You can hang a sheet of Sheetrock in five minutes. It's only hard in your mind. Get a helper and hang a few sheets.