Measuring For a Replacement Window
Properly measuring for a replacement window is essential. If you order too small, they are not going to work properly. If you order them too big, you will be ordering more windows.
Fortunately, measuring for a replacement window is very simple. Always measure the width first and height second; and whenever purchasing windows give the dimensions as WIDTH X HEIGHT. This is a must!
To measure your width, you want to pull a tape measure from the top right corner to the top left corner. Measure in that 1 1/2" pocket where the window frame slides in and measure to the sixteenth of an inch. Do the same thing at about the midway point of the window. Raise the bottom sash and do the same measurements at the bottom.
If you can't raise the window for whatever reason, go outside and do the measuring for a replacement window from there. It is necessary to remove the screen for this measurement.
All three of those measurements will probably be the same and if not; use the smallest measurement. Subtract 1/4" from that measurement and this will be the width for the new window.
When measuring for height take into consideration whether the window sill outside slopes downward for water drainage it will be necessary to measure from the highest point of the sill. Measure from the top right corner to the bottom right corner and place the tape at the top where the upper sash closes. If the bottom has a 5/8" high inside wood sill piece to prevent water from coming inside it will be necessary to raise the bottom sash and run the tape past the 5/8" sill and down to the high point of the sloped sill. Does this in the middle, on the left and take the smallest measurement, but this time deduct 3/16"? This is your height.
If you order your windows using these dimensions, they will fit right in as well as leave enough room to adjust if needed. Finally, measure the depth of the pocket where both sashes slide. Depth is referring to the point outside where the top sash rests against the outside wood stop to the point inside where the inside sash rests against the inside stop.
This measurement should be between 3 1/4"- 3 1/2". The reason you need to know this dimension is because not all replacement windows have a 3 1/4" depth frame. You want to be measuring for a replacement window that's going to fit exactly into the existing pocket of the wood frame. That means buying new wood stops for the inside of the house that are 3/4" wider than the existing stops. It is best to order the 3 1/4" frames to prevent measuring for a replacement window again.
