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I have an old wood window sill that I want to install PVC Trim over

After I scrape out, fill any rotted areas with a spackle or epoxy mix and sand what other prep do I need to do before attaching my pvc trim, caulking & repainting?

Because of the design of the frame there are infact 2 small sills where the storm windows used to be. When the windows were installed PVC trim was put around all sides of the storm window area with a quarter round base (to cover the sloped sill gap). The paint on the large sill has taken a beating, so I want to extend pvc trim over it.

I would prefer to keep self adhesive flashing tape options off the table as its difficult to find & costly. At the very least I would think priming any bare wood before installation would be the best cost effective option.

Thanks,
Mike

Window Sill.jpg581.54 KB
Asked by Mike Tew
Posted Jun 18, 2014 10:59 AM ET
Edited Jun 18, 2014 11:48 AM ET

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Mike,
Your sketch shows an unusual rough opening. However, regardless of the peculiarities of this rough opening, the flashing principles are the same.

Every rough opening needs to be flashed before the window is installed. That means that the rough sill needs a sill pan -- either a site-built sill pan or a commercial sill pan -- that slopes toward the exterior and has an interior dam. Then the rough jambs have to be flashed so that the jamb flashing overlaps the sill flashing. At that point you are ready to install the window. The head flashing has to lap the upper window flange (if it is a flanged window).

Once you have made sure that your rough opening is properly flashed, you can trim the window with PVC casing if you want.

Answered by Martin Holladay, GBA Advisor
Posted Jun 18, 2014 2:59 PM ET
Edited Jun 18, 2014 3:00 PM ET.

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