How To Install Interior Vinyl Window Casing. Perfect Minter Joints Every Time Veteran trim carpenter Jim Chestnut shares his time-tested process for installing miter joints. Run a bead of caulk on the vinyl keeping to the side of your pencil margins.
The trick is to assemble the trim with biscuits first then nail the assembly in place. This is so because it would normally match the baseboards and the other trims present around the house. To create the top header piece of the casing I measure from the outside of the left side casing to the outside of the right side casing.
Another window trim option is to use a thin reveal piece around the window frame.
Away from the jamb at both ends and along the base of the window casing. To lay out the miter joint where an eyebrow arch joins the side jambs first extend the side jamb lines up the wall. With the arch clamped in place draw a line between the inside and outside marks for the miter cut on one side. Hold the jamb frame assembly in place and mark for any scribes and cut to fit.