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Octagon windows, Bay and bow window roofs, Garage door transoms, Round"Porthole" window and Window and door canopy’s

First Line Sales, 802 257 2011,

Octagon windows, Bay and bow window roofs, Garage door transoms, Window and door canopy’s


RwCutoutInstallation Instructions for Round "Porthole" windows

Outside nail-fin dimensions are 17-1/2”, outside casing dimensions are 15-1/2”, visible glazing is 12-1/4” prox. and the rough opening is about 15-5/16” for installation from the outside and 15-9/16” for installation from the inside.



1 The unit can be; A, fastened to the outside sheathing of a project and finished with siding or trim; or, B, the window could be installed and fastened through the nail fin from the inside, as long as the siding isn’t thicker then the window casing which is about 1”.


A, If installing the unit from the outside, make a round template about 15-5/16” in diameter, cut the opening, check for a fit, caulk the perimeter of the exterior nail fin where it contacts the building and fasten the unit, through the holes provided.

Cover nailing flanges with siding or trim. Pre-drill any fasteners that go through the nail fin so as not to distort the plastic and to give it a little room to expand and contract. Install interior trim, if any.


B, If installing from the inside; carefully cut a 15-9/16” opening, the size of the window into the siding, for instance T111 (make a template), and the window can be installed and fastened through the nail fin from the inside and then caulked on the outside around the casing. Install interior trim, if any.



Note; the window exterior is clad with a durable one piece, ABS polymer cladding; and needs no finishing.

It is important that the cladding nail fin, or trim placed over the nail fin, is not nailed too tightly, use aluminum or stainless steel screws or nails and fasten through the holes provided, or drill new holes a little larger than the shank of the fasteners being used.

Stain or paint any unfinished wood surfaces, all wood surfaces must be finished as soon as possible to prevent warping. Apply a bead of caulk where the casing contacts the exterior trim and the glazing.












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The information in this web site is believed to be accurate; First Line Sales will have no liability for errors or omissions. Specifications, details, other information, etc should be verified by the user.




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