Install Window Trim Before Or After Siding

Instruction on how to install exterior 2x4 trim around a new or old window.

Install window trim before or after siding.

The wrb is lapped over the head flashing or the flashing is taped. The cement board panels are fastened to the battens. Also if the windows are of different sizes it gives the contractor a chance to make some custom changes so the window will fit properly. Nevertheless you can install the siding first if you have already started on that.

This increases the exterior wall thickness however so you ll need to extend the window. If we installed the trim after the siding we would have had to caulk a ton to fill in for the different levels the layered siding creates. Sfgate has a web page for how to install them yourself but it is very informational on the installation of windows before siding and why you should go in that order. Before you replace the siding cut and install new j channels to prevent water from leaking into your home.

Cut the horizontal piece to size and snap it in place over the vertical moldings. 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. If the trim is being applied over the hardi panels. From the top of this row and stretch a string line across the deck.

The head flashing is installed in a bed of caulking onto the top of the window frame. To provide a common reference point measure up 8 in.