Framing a corner correctly isn't difficult, but it can take time and patience. However, improperly framing or rushing to frame a corner can be detrimental to your building or remodeling project. Failing to frame a corner properly can cause headaches as small as problems with drywall finishing to a lack of structural integrity. Here's what you need to get started.
Step 1 - Laying Out and Building Corner Post
First lay your wall out, preferably on 16 inch centers (the middle of your stud should fall at a multiple of 16"). This is fairly simple starting at the end of your plate and measure over 15 1/4 inches, this will be the outside starting point of your stud and continue for every multiple thereafter. When you arrive at the end of you wall, where your corner post will be, measure out for three stud widths or 4 1/2 inches. This is marked out area is for your corner posts which will connect the two walls. While there are several ways that you can build a corner post here are two suggestions. If they are exterior walls, sandwich and nail three studs together for a strong corner. If they are interior walls, it will be three studs thick but the center space can be filled with blocks instead of a solid stud.
Step 2 - Notching your first stud and bottom plate
This step must be done prior to installing the wall because once installed, there will be no room to cut the notches. First measure up your first saw and make a mark on the farthest edge of your stud at five feet. Then measure across the bottom plate five feet and make a mark on the bottom edge of the plate. Draw a 45 degree line down and back. Then, using what will be your diagonal stud, lay it (flat side down or '4' side facing you) on the inside of the line and mark the back line at 45 degrees. Set your circular saw for 1 1/2 inches and (using all safety equipment) cut the lines first and then make several passes in between them. Once this area is cut out use a hammer and chisel to clean the notch out. Repeat for the opposite wall.
Step 3 - Leveling the walls and fasten them
Once you build your walls, use your level to get walls plumb. This may require using boards nailed to the walls at an angle to the floor or outside ground to act as bracing. Check several places along your wall to make sure you are level along the length of your wall. Once your walls and braces are set you can fasten your walls together.
Step 4 - Squaring up the walls
This is the most time consuming and exacting step but is the most important. Leveling the walls and fastening them should, for the most part, temporarily square them, but installing a diagonal stud will lock them into place. First ensure that the walls are square by using the 3-4-5 triangle measurement. First, measure up from the corner of the wall four feet and make a mark. Then measure from the bottom over three feet and make a mark. The distance from one mark to the other should be exactly five feet. If not you will have to make that adjustment. With the walls in place, take the diagonal stud and cut it to the proper length. Use the stud first to as a template to mark the studs that need to be notched. Once you mark three studs (16 inches, 32 inches and 48 inches) set your circular saw at a depth of 1 1/2 inches again and cut similar to the bottom plate and first stud. Using the hammer and chisel, clean notches up and make sure that each notch is at least 1 1/2 inches so that the diagonal stud will sit flush and fasten the diagonal stud to the original studs. Repeat for the opposite wall.