First Line Sales-Polymer Roof Factory,   PO Box 200,Vernon VT 05354,

802 257 2011, fax 802 257 0846


Manufacture and sales of ABS roofs for doors, architectural building details and

windows, including bow and bay windows


What are Bow and Bay style windows?


Bow and bay windows are valuable additions to many residential and commercial buildings. Here is a description of these windows.



Bay windows provide an attractive accent, increase ventilation and view; because the flankers project from the building and face left and right.


A bay window is actually a collection of at least three window units including a left and a right flanker usually arranged at either 30º or 45º angles and at least one unit as a center window, which may or may not open. See the pictures above they show the same sized window units being used as either a 30º or 45 º bay units. The 45º projects farther from building but the 30º is a longer window.


The window units can be either double hung (sash slide up and down) or casements (sash crank out). There are 2 flanker units and 1 center unit, which is a picture unit. Jamb sizes of units are usually 4-9/16” (depth) to fit 2x4 framed walls and 2”jamb extensions are added 2x6 walls.


The designation of the assembly often consist of the angle and the name of the units, for example a double hung 45º 3442-18 would be 45º angle, 34( prox. 41” w, 36” visible glass width x 42 (prox. 52 H x 35 w visible glass) high center unit and 1’-8” (prox. 20” width, 16” visible glass width) flankers, 42”high.

Casement bay units are named much the same way although some manufacturers may have their own numbers for the unit.


Bow windows are assembly’s, like bays, but they are arranged at a much lesser angle, for example 10º or 12º, and bow windows usually do not project as far from the building as bay windows. Each window assembly is usually made up of the same size casement units and all units open. They can often have, 3, 4, 5 or more individual units.


11 November 2017