Figure 1 - Casement replacement window
If you are planning on purchasing replacement windows in your home, there is one simple trick to a proper installation and that is measuring!
It does not matter what style of replacement windows you are using or what style of window you are replacing. You must have the correct measurement of the space where the window will reside
Additional information on window styles
Their are a couple of decisions that you must make before you even begin taking measurements.
Do you want your replacement window to sit inside the old window frame or are you prepared to remove the trim and window frame in order to install a complete new window. It is of course easier to install a new window into the old window frame, however if the old window frame is badly weathered, this may be the time to replace the entire window and at the same time insulate between the window frame and the wall studs.
If you are installing the new window into the old window frame you should:
- Measure the diagonal to ensure that the old window frame is square, as shown in Figure 2.
- Measure top, bottom and middle in horizontal and vertical positions, as shown in Figure 3.
- Take measurements to 1/16 inch.
Figure 2 - Measure the diagonal of the old window frame
Figure 3 - Measure top, bottom and middle in horizontal and vertical positions
If you are installing the new window into the old window rough-in framing you should:
- Remove all window trim to obtain access to the old window rough-in framing.
- Measure the diagonal to ensure that the rough-in opening is reasonably square, as shown in Figure 4.
- Measure top, bottom and middle in horizontal and vertical positions, as shown in Figure 5.
- Take measurements to 1/16 inch.
- Use the shortest measurements as the measurements to use to designate the rough-in opening. Shims will be used to level and square the window at the time of installation.
Figure 4 - Measure the diagonal of the rough-in window opening
Figure 5 - Measure top, bottom and middle in horizontal and vertical positions
Use a "good" tape measure. A tape measure that does not have a broken or damaged tip.
When ordering the window, make sure you tell the manufacturer whether your measurements are to fit into a pre-existing window frame or a rough-in opening. For a pre-existing window frame, the window will have the exact outside dimensions that you supply. For a window that is being installed in a rough-in opening the window frame will be a 1/4 inch to 1/2 inch smaller than the opening to allow for shimming the window square and the addition of insulation between the outside of the window frame and the wall studs.
A window that screws through the window frame into the stud is designed for the placement of a molding on the outside of the window frame or in some cases caulking is sufficient as is the case with a brick or stone veneer wall.
Figure 6 - Nailing flange on replacement window
The second decision, which is only relevant if you decide to remove the current window frame is the mounting style of the new windows. Some windows require mounting from the outside using a flange that is nailed into the studs, as shown in Figure 6. Other windows require that you screw through the window frame into the stud.
A flange mount system is designed to have a finished material placed on top of the flange. Material such as wood or vinyl siding.
All replacement windows will require caulking on the outside to prevent air leakage and moisture and water ingress.
Window replacement is a project that the home handyman can undertake. Depending on the size of the window it may be necessary to have an able body helper to assist in lifting the replacement windows into position and holding them in place while they are being attached to the window framing.