Step 6: Framing Basics
The first construction step is going to be framing up the walls. To successfully frame your garage you need to decide where all your openings are going to be (windows and doors) and plan for the sheathing on the outside and any interior covering (drywall, plywood) you plan to use. I framed my garage in 24" on center stud spacing but the same approach applies to 16" on center construction. Based on my site plan and elevation drawings, there are more openings on the east wall, with the access door and one window. Thus I am going to start there.
The first step to framing up the east wall is to measure the width of the slab/block. As designed mine is right on 20' within a half inch. Take this measurement and cut AC2 treated 2x4's to make the bottom or sill plate. Any lumber that contacts masonry must be treated to prevent rot. Keep in mind that building code requires that any cuts in the sill plate be anchored with bolts within 12" from the cut on both sides of the cut. Place your cuts accordingly or buy a longer piece of wood. If you plan ahead you can have the concrete guys put in some extra anchors for this purpose. With the sill plate cut, lay it on the slab/block and transfer the positions of the anchor bolts onto the wood. Make your marks so that when the sill plate is mounted on the bolts it will be flush with the exterior surface of the slab/block. Then drill holes in the sill plate large enough for the anchor bolts to clear (~3/4" ) and make sure all the bolts will fit through at once without too much binding. Leave the sill plate on the bolts on the slab/block.
Then measuring from the outer edge, make marks on the top of the sill plate every 24". If the marks overlay any of the anchor bolts you may need to notch the corresponding stud or cheat the stud to one side or the other. Also mark the opening for the door. Typically, the opening for the door is 1.5-2" larger than the door itself. So for a 32" door you need a 33.5-34" opening.
Next, cut regular non-treated 2x4s to the same total length as the treated sill plate. This span should be made up of 2 pieces or less. This is the first layer of the top plate. Then take the sill plate off the bolts and lay both the sill plate and top plate next to each other and transfer the stud measurement marks to the top plate. Now lay both the sill plate and the top plate on an open flat area such as the slab about 8' apart. Now get your 8' studs and start laying them in place at the marks. Before you start nailing, let's talk about openings.
The width of an opening for a window or door is defined by the distance between the innermost jack studs. The jack stud runs uninterrupted from the header to the sill plate and provides support. Nailed to the outside of the jack studs are king studs that run from top plate to sill plate like normal studs. Generally you want one of the king studs to be on your 16" or 24" spacing pattern. Above the header and below the top plate are so-called cripples that are placed on the 16" or 24" pattern. At the bottom of the opening (for windows) there is a saddle stud that is toenailed into the jack studs and supported by more cripples that go from the saddle to the sill plate. See the sketchup diagram below to clarify. It is very helpful to have your openings planned out before framing so you can quickly measure and cut the required lumber. The header is often made from a pair of 2x6's cut to width and nailed together with a spacer in between to make the total header thickness the same as the wall. In the case of 2x4 framing where the wall is about 3.5" thick the pair of headers will be around 3-3.25" thick and a spacer can be omitted if you are lazy.
Another thing to note is that your starting wall will be the full width of the slab/block foundation. The subsequent side walls will overlap the ends of the first wall. As you can see in the opening framing sketch below I have added an interior wall stud that allows the creation of an interior corner for screwing/nailing your interior finishing material to the framing. See the corner framing sketch to get a better idea of how this occurs. The sketch is a cross section of the framing at the corners of the walls. When wall#1 and wall#2 come together, the end studs will sit such that there will be no way to attach the interior sheathing to the framing of wall#1. Thus an "interior wall stud" is added. I have no idea what this is called, so take that name with a grain of salt. I suppose I should name is something catchy like "queen stud" or "naughty in the corner stud". I leave that to the experts.
With your openings and corners planned you can cut the lumber and start nailing through the sill and top plates into the studs using the power nailer or your own elbow grease. You want two nails per connection. There are a couple of types of nailing connection, that I will call end nailing, toe-nailing, and bond nailing. See the sketch below to get an idea of how these are done. The only one that can be tricky is toe-nailing, but you will get the hang of it. For attaching the studs, jack studs, king studs, cripples, etc to the sill and top plate you will need to put two end nails into each stud through the plate as drawn. You will use bond nailing to attach the headers together and to attach the jack to the king studs. You will also end nail the headers to the king studs and the cripples to the saddle. The only place you need to do toe-nailing in most framing is to attach the saddle to the jack studs and to attach upper cripples to the headers. Go to it.