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Replacing windows and exterior window trim is a remodeling task that I do quite often. Sometimes, I am called when a faulty installation has caused a catastrophic failure, and I end up rebuilding the opening, then reflashing and retrimming the window from scratch (see “Fixing a Poorly Installed Window,” Feb/19). I also do complete window replacement projects (see “Retrofitting New Windows in an Older House,” Apr/15). In both of these situations, I typically tear out the old wood trim—including the windowsills—and replace everything.
In some window projects, however, I find that some of the existing trim is in good shape, so I replace just the sections that are rotted to save the client the added expense. That often means replacing just the sill or just the casing.
I recently returned to a replacement window project that I had completed some years ago. In that case, the 1 1/2-inch-thick old-growth wooden sills had been in great shape at the time, so I left them in place, though I replaced the rest of the trim with PVC. Those sills had finally given out, and it was time to retrofit new ones. My first task was cutting the nails attaching the old sills to the original jambs and removing them. The new PVC sills matched the original sills and slid in easily from the outside. Adding the PVC sills brought all the window trim up to date and will keep the windows performing well for years to come.