Install Window Trim Before Or After Siding

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.

Install window trim before or after siding.

As long as the old siding isn t bulging or falling off you can usually install vinyl siding right over it. Instruction on how to install exterior 2x4 trim around a new or old window. 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. From the top of this row and stretch a string line across the deck.

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. 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. Before you replace the siding cut and install new j channels to prevent water from leaking into your home. This increases the exterior wall thickness however so you ll need to extend the window.

If the trim is being applied over the hardi panels. Begin by installing the first row of siding on both sides of 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.

Nevertheless you can install the siding first if you have already started on that. Cut the horizontal piece to size and snap it in place over the vertical moldings.