Why do standard window sizes vary by manufacturer?

On the west coast, architects have a common practice of using “nominal” sizing for windows where the rough opening (the framed wall opening for the window fit into) is a standard size, such as 5’ wide by 4’ tall. Following World War II, there was a major building boom in west coast states and high aluminum supply (used for the production of bombers and fighter planes during the war). These two factors led to the installation of standard size, easily-produced aluminum windows in our area.

However, in the east and Midwest, window manufacturers historically produced windows with a different sizing scheme; their window sizes were based on standard “daylight” or visible glass sizes, not the window’s rough opening. Architects and builders everywhere but the west built their rough opening to accommodate the window manufacturers’ specifications.

As window and door sales become less regionalized, interference between the two sizing systems has developed. In our area, many architects will still design houses with nominally sized windows and doors. This works well with the sizing flexibility of aluminum, vinyl, and fiberglass windows.

However, if you choose to use a wood window from a Midwest manufacturer such as Andersen (Bayport, MN),Marvin (Warroad, MN), Integrity (Grand Forks, ND), or JELD-WEN Premium Wood (Hawkins, WI), the manufacturer’s rough opening may be a different size than the rough opening framed in your house.

Changing over existing production processes to accommodate “standard” sizing is a difficult endeavor for manufacturers of wood windows, however many of the top companies are introducing new nominally sized windows that allow you to choose custom sizes. These can be costlier, and if you decide to use wood windows and doors, we can provide you with a list of rough opening sizes so that your contractor can accurately frame your window and/or door openings.