Exterior window trim when using 2×8 “half log” shiplap siding
Windows and the exterior door are all Andersen, clad, and you know how much frame projection there is outboard of the flange. Same as most all clad windows, a teensie bit more than one inch. Due to the thickness of the “faux log” siding boards, about 1-1/2″ at the bulge, the exterior casings and sills will need to project out at least 1-3/4″. The idea is to use roughsawn 2x lumber for this, and then dress one side of the boards so all are the same thickness. Instead of doing a board as a sill, I thought we might flat-case the bottom same as the sides, but then use a router and 15-degree chamfer bit to mill a stopped “sill slope” into the inside edge, stopped so that it ends at the sides right at the side casing junction. But all that is just an image in my head. What do you do when using thick trim like this?
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Your idea would have the added advantage of making it easier to replace the windows.
I've done it before with
I've done it before with vinyl windows that didn't project far enough, they got flashed to the typar, and the frames got preassembled, clam clamps, and a stainless 3" screw at the corners (and plenty of TbIII). I made the frames slightly larger (the trim and siding was maibec pre-finished cedar), and then ran a bead of caulking around the vinyl frame. As a second layer of protection we put white drip cap on top of the applied wood frame also flashed to the typar. double protection.