An overwheleming majority of New England homes will have to undergo some sort of rotten exterior trim replacement at some point. One of the most common needs is replacing rotten window casings and sill noses, especially on the north and east faces of a home. This article aims to instruct how to replace your exterior window trim with glued and screwed pvc window trim, in a manner that will withstand the elements.
This home in Portsmouth, NH was in need of these repairs. Although I have no photos, the first thing to be done is remove the existing window casings and sill nose, gently, so as to not destroy the existing jambs, etc.. I use my Fein reciprocating saw to slice through these components, for easier removal. The sill nose must be trimmed flush with the jambs.
After measuring for the new trim and cutting and labeling the new pieces, it’s time to begin the assembly. The first thing I do is to assemble the bottom of each side window casing to the sill nose. In this case the bevel angle is 15 degrees. The glue we use for pvc welding sets up relatively quickly (in about 5 minutes), so we’ll want to start our screws before applying the glue. Because the sill nose (made by Royal Moldings) is only about 1-1/8″ thick, we can screw from the underside of the nosing into the casing. The rest of the pvc trim is Azek brand.
For screwing the tops of the casings together, we rely on what’s called a “Kreg” brand pocket screwing kit from the back side of the casings. We first drill the pocket holes for the screws on the back of the side casings. Next, we make sure we’re using the right trims in the right spots, that’s why we mark such as “TR” to mean Top Right corner of the window. Now start the screws into their pocket holes before applying glue. Glue it up, and then use the special clamp and a backer block to protect the face of the trim during clamping. Screw it together and that one’s done!
Next, we must prep the face of the window jambs and sill nose before applying the new trim. We use Lexel brand adhesive caulk exclusively for anything that has to hold up to the elements. It has tremendous adhesion, uv resistance, and flexibility. The flexibility is key. You don’t want to use an epoxy paste or
anything that won’t move and expand and contract with the movement of the vinyl and wood components. We apply this liberally to the sill nose and bottom portion of the jambs.
It’s time to install the trim. We use screws for greater holding power to stay bonded tight to the wood. The screws we use are made for pvc trim. They use a special driver to recess the screws into the face of the trim. Then you gently tap a matching pvc plug into the hole, and the hole has vanished! We clean up all the excess caulking using mineral spirits and a clean rag. Remember not to leave solvent soaked rags bunched up
in the sun or high heat (like an attic during the summer). The rags will spontaneously combust. Instead, drape the wet rags to dry immediately after use.
Once all the plugs are in, we wipe down the trim with the Goof Off, and then install the storm window and it’s complete. The total time for this project (an easy first story window) is under 3 hours. The total cost for this window was around $200. In this case, the critical joint between the new sill nose and the existing sill is hidden from the majority of the elements behind the storm window. If there is no storm window, I recommend checking the integrity of this joint and re-caulking if necessary every few years, just to err on the side of caution. I warranty this project for ten years, but you can expect it to last much longer.
By John Bradshaw