Window archways solve the problem of poor, crooked and out-of-round reveals for vinyl and aluminum windows. Our window arch kits also provide a weather tight seal and easy insulation. 1" to 5 ". Any depth over 5" will be made as a split (a 2" arch for both the front and back of the opening). Lastly, a window arch depth is limited to 18. Anything greater than 18 is considered a barrel vault. The rise of your window archway is the window height less the window leg. If your window arch doesn't have a leg, then your window arch rise would be the sames as the window height.