Add building paper which should extend behind the window s nailing fin.
How to add exterior window trim on vinyl siding.
Notch the vinyl windowsill with tin snips to fit the existing windowsill.
Exterior window trim on vinyl siding if your home has vinyl siding and you d like to add vinyl window trim you will first need to remove the existing siding and j channel from around the windows.
If you see any holes in the building paper.
Unscrew and remove the storm window from the outside of the window.
Pry off the vinyl siding and j channel from around the perimeter of the window.
Because the vinyl siding on the exterior of the window does not provide a 100 waterproof barrier it s important to also install building paper and flashing to avoid water getting in and rotting the wood beneath the window.
Use tin snips to trim off the metal flashing covering the exterior windowsill.