Hi XXXXXXXXXX;
Measure the rough opening and then subtract a half inch from that measurement. That is the size window you need to order.
If the measurement is not a standard window size then you will need to add furing until the dimention is within 1" of the standard window size.
Best, THS
Furring is the term carpenters use when they add another piece of wood to decrease the size of an opening.
You can do this yourself. If you have never installed a window I strongly suggest that at minimum you find someone that has, and have them help you. You will need a helper anyways. Installing windows is a two person job.
The installation really isnt difficult, but in many ways it can become a nightmare. If you do not install it correctly it can cause problems in the future. It can leak if not properly flashed. It can jam when the house breathes with the weather changes. It can even break for no apparent cause.
The most important thing is to be sure that the window is square when it is nailed in. Check the reveal on the sliding part to the stationary part. This is basicly the eveness of the opening all the way acrost the the bottom with the window just about all the way closed. It shouild not be any doiffrent on one side as the tother. If it is then the window is not installed correctly.. You will need to shim it up so that the reveal is the same all the way actrost the bottom.
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