Don´t forget that one of the benefits of siding your house is that you can fix things that might not have been done right the first time, or are worn out. This would include flashing windows. The entire process of properly flashing windows is covered in our Windows Section, but I do want to mention it here. Flashing your windows prevents wind and water from getting in. It also helps shed water in the proper fashion, so be sure to check out that section before installing the J-Channel.>

Existing Wood Trim

In some cases, you might have wooden trim around the exterior of the house. What you do with this will depend on how you intend to finish the trim. Since there are so many possible problems for you to deal with, I´m going to pick a common one and leave the rest to be answered on our forum.

On occasion, I run into wood trim that has butt joints and the top overhangs the sides. You basically have two choices with this problem, you either are leaving the trim (possibly repainting) or you are going to have to cut the extra off and wrap metal over top of the wood trim. This gives a very neat finish and is very low maintenance. If you have installed new windows, you might not have to worry about any of this, since you can simply remove the trim and use J right up against the New Window.

For our example, we´ll cut the trim off and apply the metal wrap. This will be done at the end of the project, once all siding is installed, but we do have to cut the top pieces in preparation for flashing and then for the J.

J Channel

J channel gets it´s name from it´s shape. If you look at the end of a piece, it looks essentially like a J. The siding will slip into this J and it covers the edges. With most windows, you should be able to use 2 pieces of J to wrap around the window, one piece covering the bottom and one side, and the other covers the top and one side.

Bottom First

There are fundamentally two different ways I have seen J wrapped around a window. The Butt method, and the Mitered method. The Butt method is a bit quicker, but I feel the Mitered method has a neater appearance and the extra time isn´t a problem, so that´s the method I´ll demonstrate next.