Step 21a – Install 4/4 HardieTrim

Trim siding is used primarily for visual purposes, but is also a great tool to use when it comes to weatherproofing corners of the house. You want the corners to match up tightly with each other so they form a nice seal, and it is much easier to match up 2-4 vertical pieces of trim siding in a corner than it is to match up 30-40 individual rows of siding. Either way, remember that siding is not waterproof, and must be installed in accompaniment with a water resistant barrier and a moisture management plan. I designed the house to have trim siding in the corners, but also around the windows and along the rim joists to give it a little curb appeal.

The manufacturer of the trim siding I am using (James Hardie) recommended using stainless steel finish nails to attach it to the furring strips, but my all electric finish nailer simply wasn’t powerful enough to fire through the fiber cement. I was left with the decision to either buy a new finish nailer or to attach the siding with trim screws. I really wasn’t happy with either choice but I decided to use the screws because I would have had to buy not only a new nailer, but also an air compressor, since my other nailers are all electric as well. Using the trim screws was also very frustrating, however, as they used a #1 square drive which kept stripping, and the stainless screws were quite expensive.

I started on the window trim first. For each window, I first installed the side pieces, cut to the same height as the window, but with a 10 degree bevel on the bottom. This bevel will match up with the sill trim so that it gently slopes away from the wall, helping to direct water away from the window. The next piece to go on was the head trim. I cut it 3 inches long on each side, ripped it in half on the table saw, and then cut one of the pieces down an additional 3 inches. This allowed me to give each layer an overhang of 1.5 inches on each side. I furred out the second layer of head trim with some 1/2″ plywood to give it some depth, and then added one more piece on top with 45 degree miters on the ends. I furred this last piece out with 1×4 so it extended just slightly out from the piece under it.

For the sill, I ripped a piece of trim in half and then beveled it 10 degrees. I cut it 3 inches long so it stuck out an inch and a half on each side. I also cut a drip groove in the bottom. Water has this amazing capability of sticking to things even so much as to defy gravity, so this groove will ensure it will pool together enough to drip.

Below the sill I cut one last piece with a ten degree bevel to match the sill. Each of the cuts were painted with high quality exterior paint before installing. This is also specified by the manufacturer to protect the siding so it will last as long as possible.

I finished each window off with a galvanized drip cap. This will prevent water from pooling on the flat part of the trim.