Install Window Trim Over Siding

Here is one great way to trim out a window or door opening with aluminum coil when using progressive foam insulation for plank style sidings such as fiber ce.

Install window trim over siding.

Make sure that a drip cap is installed first over the window before going for the hardie siding. This meant our new windows would have trim that was much wider than our old windows making it necessary to cut away a bit of our siding to sit flush with the edge of that new trim. You will see the trims lay nice and flat. Building paper is an important part of the wall s waterproofing.

In order to get the most accurate cut line we decided to place our new window in the opening to trace it. Slide the top edge under the window fin then nail off the fin with roofing nails. The head flashing is installed in a bed of caulking onto the top of the window frame. Level and tack the new window in place then cut a piece of aluminum flashing to width so it extends from the new window to overlap the nailing hem of the siding below.

The rain screen battens are run down to the top of the window flange. The wrb is lapped over the head flashing or the flashing is taped. Face nail trims using 2 inch 16 gauge finish nails after every 16 inches apart. Before you replace the siding cut and install new j channels to prevent water from leaking into your home.

We used pressure treated 2 x 4 s for the trim around the windows and the doorway and then we had to create trim corners for both the inside and the outside corners like the ones in the picture above. Touch up the divided hardie trim boards before trimming them to your window. The cement board panels are fastened to the battens.