Whether you are building it during the construction of a new home, removing an older window frame, or simply building a new one in a solid wall, there are a few main elements and steps you need to know about framing a window. It is a simple process, that necessitates a few tools, materials, and some useful information. Even if we are talking about different window styles, varying from house to house, installing a new window usually requires demolition and framing. The steps below describe the window framing process.
Step 1 - Measure the rough opening
Measure the vertical and horizontal sides of the opening for the rough frame, and take care to set its dimensions 1-1/2 inches wider and taller than the window you want to install. Measure another 3 inches on each side for the king studs and the jack or trimmer studs. If there is a wall stud right up close that could be used as one of the king stud framing one side of your opening without causing any issues with the location of the window in the wall, using it as a starting point could save you extra work and lumber.
The king studs are the main vertical posts that run from the bottom wall plate to the top wall plate of the wall frame on each side of the window. The jack studs are shortened vertical posts fitted between the header and the bottom wall plate or soleplate. They are superimposed and nailed to the king studs on both sides of the window to provide support for the header which is the large horizontal piece at the top of the opening that runs the full width of the window opening and sits on top of the jack studs. Cripple studs are short vertical posts placed between the header and the top wall plate and also underneath the opening between the sill and the soleplate.
Step 2 - Cut, fit, and nail the king studs
Cut the king studs, so they connect the top wall plate with the soleplate and fit on the outer edge of the opening. Nail them to the top plate and the soleplate. The top plate of the wall framing is usually a double plate and is the horizontal beam where the ceiling joists are resting. The soleplate is the horizontal beam at the bottom, where the wall meets the floor. Use 2 nails for each end. Check if they are plumb with a level.
Step 3—Place the jack studs
Cut the jack studs, making sure their height is 3/4 inch longer than the height of your window's header once installed. Place them inside of the window opening against the king studs and nail them together, on both sides of the window opening.
Step 4—Cut and fit the header
The header is the large horizontal beam at the top of the window framing. Measure, cut, and nail together 2 sections of 2x6 or 2x8 lumber, and position them on the top of the jack studs. Toenail the header into the king studs so that they come flush to the wall frame on both sides. Since the two adjacent pieces only add up to 3-inches, an in-between spacer can be made from 1/2 inch plywood to make up for the 3-1/2 inches thickness of the wall frame.
Step 5 - Install the window sill
Cut the sill to the length equal to the distance between the jack studs. Mark at every 16-inches on the soleplate and the sill piece, where you'll need to place cripple studs. Cut as many pieces as needed from 2x4 lumber. Nail all the cripple studs to the sill plate then take that sub-assembly and place it between the jack studs within the wall frame. You can then toenail the sill to the jack studs and the cripple studs to the soleplate. For good measure, two extra cripple studs can be added up against the jack studs for more stability.
Step 6 - Place the top cripple studs
Mark on the top wall plate and on the header where you will need cripple studs, every 16-inches apart. Measure the height between the top wall plate and the top of the header and cut as many cripple studs as required from 2x4 lumber. 2 extra pieces can be also added here for stability. The shorter studs can then be toenailed in place between the header and the top plate. This is the last step in how to frame a window.