discussion on adding 2nd story above garage

[EricU]

our neighbor did this, then he got divorced.  

I really wanted to do this to our house, because the bedrooms are just too small.  I would love to get rid of the one that is smaller than most master bedroom closets.  But there really is no need.

[MstrCarpenter]

I've done dozens of roof raises. I can see two of them from where I'm sitting (not including my own). The quickest weather-tight shell was right after a two week vacation. Two carpenters, two helpers, two days. That was a Cape with a 12/12 gable roof to a Salt-box (2 stories in front 1-1/2 in back) w/an 8/12 pitch. I have to admit that only about 5' of shingles were on, and only because the tarp wasn't big enough. I did one to a garage in 4 hours after a full day of prep. We cut the rafters and ceiling joists free from the walls and center beam and added braces to make them queen trusses. We also framed and sheathed the four walls in the driveway, then added Typar and strips of ply to the shoes. The crane we hired had a four hour minimum so as soon as he set up we had him lift the roof off. We quickly framed the new floor and spread out some sub-floor to walk around on, then we were ready to put the roof back on with one minor twist. Rotate it 90 degrees. We had some time so we had the crane lift all our windows up to the new second floor. We finished up the day installing the sub-floor, putting in windows, and started the strapping. The framing was far from over because we still needed to demo and stick build a half story over the breezeway for a hallway to the main house, but that garage went from one story to two in two days.

As jasfrank wrote, it does take a strong commitment to logistics;  You need almost all the materials at the start. The dumpster has to be right under where you're working but needs to be moved before you use all the materials. You'll be laying out plates/shoes, and rafters before you even have a floor and framing for windows as fast as your cut man can supply parts from the cut list. The roof won't come off 'til tomorrow, but it's been braced and rafters cut into 4' sections. Day two is mostly material handling. There's very little measuring or cutting; just put in place and nail. Route the rough openings, typar, add hurricane ties then lift the wall. Repeat, repeat... Nail ceiling joists, rafters, sheathing. Time for windows, a tarp, and a good nights sleep!

I would guess that less than 50% of the roof raises and other additions I've done have utilized a "professional" Designer or Architect. I make them look like they've always been there or sometimes, purposely, make them different yet complimentary to the original architecture. And one more thing. "value engineering" should not be confused with "cheaper"!

[bestbuyfloor123]

Really nice plan but be sure to check all the materials. It will be a very rare garage that is built strong enough to support a second level of any sort.

[FS7]

Unless your garage was designed initially with a living space above it, most builders would use standard roof trusses with 2x4 bottom chords. It's my understanding that they can handle a low dead load (their own weight and the ceiling drywall) and are not rated for any amount of live load. Of course, thousands of people happily put plywood down and use it for storage with no ill effects. Electricians walk around up there on the trusses with no consideration for collapse. The only time I've ever seen something bad happen is when roof trusses were cut, which of course caused the roof to sag. If they hadn't, even though the original design didn't support a living space it was certainly doable.

In general, if you want to actually expand an area above a garage into living space, you have to evaluate the structure. Bottom chords are not meant for that, even if you sister larger boards to them and try to distribute the load. If you only wanted to store Christmas decorations, baby stuff, and whatnot, then don't worry about it.

I have an area above my garage that could be a decent 12'x20' game room, but it wasn't built that way in the first place. At some point I'll get around to seeing what I can do.

[Cooler]

Two of my neighbors "built up" on their houses.  One had an architect that beautifully integrated the design to the original architecture.  The other looks like a kid with Legos designed it.  

My assumption is that in both cases the engineering was done correctly.  But clearly different talent levels were involved.

I would ask to see photos of similar jobs of the architect or builder so you can evaluate their design sensibilities.  I would ask for three references (minimum), one from each of these categories:

1.  Recent.  Within the last 6 months.
2.  Fairly recent.  Within 2 to 3 years.
3.  Not recent.  Over 5 years.

I would be less satisfied if all the references fell within the same time period.

[EricU]

One of my neighbors did this, it looks okay.  The addition is in the back, you can't really tell it was done from the front.  I think that's a good idea.

I don't miss hearing him screaming at his family because of some mistake they made helping him build it.  His wife left soon thereafter.  That's not uncommon with additions, but I'm a little surprised it took that long.

LOML and I had discussed doing this.  I don't see any good reason for it to happen.  It occurs to me that if we continue to live in the house, a master bedroom addition on the first floor level is the thing that makes the most sense.