Installing Vinyl Siding
There are two basic steps to installing vinyl siding: installing the trim pieces and installing the siding itself.
Choosing and Installing Trim Pieces
Every place where vinyl siding joins something else—a window, a door, another wall—requires the appropriate trim piece. The trim pieces loosely hold the siding in place, cover any cuts, and provide a small space where the siding can expand and contract. All lines of vinyl siding come with several standard trim pieces, plus some extras.
Most of the time the bottom of each piece of siding locks into the piece below it. But for the first row on a wall, the bottom locks into a special trim piece called a starter strip.
An outside corner post is used for outside corners. There is a channel molded into each side of the post to receive the end of the siding.
There are several options for trimming out inside corners. The easiest is an inside corner post. It's also possible to use two piece of J-channel installed back-to-back to create the same effect.
Many professional siding contractors bend a piece of vinyl or aluminum flashing for the inside corner and then use a single piece of J-channel. However, this requires a sophisticated tool called a brake.
J-channel is the most common piece of siding trim. Besides being used for inside corners, it's used for trimming around windows and doors. It is also used where siding meets a soffit or roof at an angle.
At the top corners of windows and doors, the two pieces of J-channel should be mitered and overlapped carefully so that moisture is directed down and around the window and doesn't get a chance to seep behind the siding or trim.
||J-Channel used for inside corner
||J-Channel around a window
Where siding runs up into a horizontal surface (like under a window or at a soffit) you need a piece of undersill trim. In these situations the top edge of the siding will usually have to be cut to fit. The undersill trim is designed to grab this cut edge and hold it in place.
Siding pieces generally come 12 feet long and between 10 and 12 inches high. The bottom of each piece hooks on to a lock molded into the top of the piece below it (except the first piece on the bottom, which locks into the starter strip). The top of each piece is loosely nailed into the studs, or into wood sheathing.
The ends of the pieces are hidden by corner posts or J-channel. There should be about a ¼" gap between the end of the piece and the inside of the channel, so that the piece can expand with changes in temperature.
Pieces should overlap by about an inch. Again, this is so that the material can expand and contract without exposing the sheathing underneath.
If nailing too tight is the MOST common do-it-yourselfer mistake, the SECOND most common do-it-yourselfer mistake is to not pull each row up properly as you nail it. You need to pull up each row firmly and consistently so that it locks solidly into the piece below it. That way, you're getting the full height out of each piece of siding and the siding has a consistent vertical spacing all the way around the house.
Where you need to cut the siding horizontally to fit or under a window in the space left at the top of the wall, you need to create small tabs along the cut edge with a snap lock punch. The tabs will lock into the undersill trim and hold the cut edge in place.