I have been putting quite a bit of fiber-cement siding on Habitat houses. There are several ways to make up the corner boards to hide the ends of the lap siding. Sometimes, we use one piece of 4/4 stock and let it extend a full inch beyond a corner. This one piece will hide the siding ends on two walls. Sometimes, we use a traditional two-piece corner board made of 4/4 stock. This consists of a 1x4 on one side matched to a 1x3 on the other. We usually take the time to screw these two pieces together before installation. At still other times, we use the metal corners that slip over the ends of the siding.
On single-story homes, lately we have been taking a 10-ft. 4x4 and cutting out a one-piece corner, as shown in the drawing (left). I typically cut with a circular saw. The inside of this corner will not be seen, so it doesn’t have to be cut with total accuracy. After setting the saw to cut about 3° off square, I cut the full length of the 4x4, leaving about 1 in. on each side. I then run a router on the outside edge to leave it looking nice and trim. Finally, I give both the inside and the outside of this corner piece a good coating of paint or oil.
We make use of the material that is left over from cutting the 4x4s by ripping it to about 11⁄4 in. sq. and using it on the inside corners. It can be hard to fit this piece of trim tightly into a corner because the housewrap holds it out a bit, so I bevel the back edge to allow it to fit snugly.
Larry Haun, Coos Bay, OR