Photo 8: Install J-channel under the window. Position the J-channel under the window. Cut and position an undersill trim if necessary (see ‘When to Use Undersill Trim.’). Drive roofing nails every 8 to 10 in. through the middle of the slots. Don’t drive them tight. The vinyl siding trim pieces should slide back and forth slightly.
Install siding at the top of a window or door in a similar fashion, but this time set the siding on the window channel and use the window trim to mark the cut. Step 20: Meet the Soffit
J-channels are used around windows and doors, on inside corners and where the siding meets the soffit or roof at an angle. Simply slide the siding panel into the folded J-channel. Well-done installation of the J-channel gives the vinyl siding a professional look in corners, doors, windows and other edges of your home.
Cut and install the bottom J-channel. Measure the width of the window. Add 2 inches to that number and cut a length of J-channel to this measurement. Score a 1-inch notch along the top side of the J channel on each of the ends. Use the tin snips to cut into the corner of the scored notch on a diagonal. Break off the resulting pieces.
Minimizing J-channel takes planning and creativity. When I know a house will be sided in vinyl, I select windows that have either an integral J-channel or a slot to receive an applied cap that creates a receiver channel. Alternatively, I use vinyl window and door casing, which is essentially a 2-1/2-in. wide J-channel.
Georgia-Pacific J-channel Teak/Pebble 1.75-in x 150-in Vinyl Siding Trim Georgia-Pacific Inside Corner Post Gray 1.5-in x 120-in Vinyl Siding Trim Georgia-Pacific Cedar Spectrum Vinyl Siding Trim Outside Corner Post Bayou Blue 3.5-in x 29.125-in
This does not appear to be a type of window designed for installation with plank siding (unless the siding is shoved into a very deep integral J channel with the back flange of it concealed by the siding) - looks like a "flush mount" window to go over panel siding or brick (though would still need the water shield, flashing, etc in that case.).
Installing it correctly will make the difference in whether your window is subject to leaks or not. Follow the below steps to add J-Trim to your siding. Step 1 - Prepare Windows . Before beginning installation of your J-Trim, ensure that the top of the window is equipped with drip flashing overlapped by felt paper.