Sorry, I missed the update on this thread...
re:
1) Mine over the garage door is 3 feet, that was plenty of room for large bins, yeah there was waste there but that was as far as I could reach kinda safely reach on a ladder (i just climbed a ladder and guessed reaching my arm out). My sides are 2 feet.
At 4 foot if you drop or shove something back there not sure how you'll get to it, some access i guess in the middle like that site. I had looked at that site a pretty good bit as well.
I can tell you I wouldn't want more than 3" i have to use a pole or climb damn near on top of the ladder to reach the back wall especially in the corners..and that isn't too safe. I'd want 4' or >4' with a couple of access holes.
At 24" over the garage door, that's about like mine...i didn't see the need to go say 4-5 feet and have access panels like in that pic but could be handy i'm sure if you want more space...just have to have access panels at that depth.
2) 16 seems way overkill...mines every 24.
3) I can't really comment on this, my garage walls were block so I used redheads, i do have one short wall studded which yeah i used 1/4x4 but it was my back where i have a 2 footer. I usually use around that size for wall storage so seems ok to me.
The only thing i really did different than those loftbuilders is I ran theaded up above the joist so the steel channel spanned two joists, and i dropped it down (so weight is pushing down instead of pulling). I've had the garage overhang metal racks lagged in like that with tons of weight, i just felt more comfortable with this route (as well as visually).
You probably don't even need 2bys, the difference in cost was negligible and the 2 bys at depot,etc are usually staighter anyways so i just used those. The cost is in the hangers if you go that route, theaded rod, channel, and the ply...but with 24 center i used really thin plywood...plenty of support.
Here's how i did mine..
Basically i lagged a level 2 by ledger all the way around, nailed my hangers on the ledger every 24 center (I chose the middle of the garage door, marked then worked 24 out so bit off on each side at the ends but a bit cleaner visually). My front rods are like at 5 or 6 foot points so -----* -----*----- ...no thought here, just seemed even and good distance a 2 by could easily span.
Then I figured out depth (3 on back, 2 on sides) and measured and dropped my rods..put the 2bys on the front (drilled the holes for the rods), then i just cut and installed the joists. I did not use hangers on the front...just nailed them. (screws would probably be a bit better but I didn't feel like pre-drilling). So for the front just measure your depth, then temporarily support and nail a scrap board across the top of the ledger and front to get it all lined up and install your joists. Though a couple of times i dropped my rod first and went ahead and ran it through the front, just whatever worked.
Mine is pretty overbuilt, i don't have a ton of experience with this stuff so i usually end up going a bit overkill from lack of knowledge. But like I mention, a couple of 200 lbs dudes could jump and hang off it and it not budge and i've loaded the **** out of it lol
oh also for this type stuff i use my finish nailer a lot with 4" nails, helps me just to get everything set (can be easily pulled apart if i screw up), then i put the real nails or screws in. So like for my joist i hang em in the back nailed, finish nail the front bam bam bam then i'll go back and sink a couple of nails in each one on the face.
