Hanging the Corners
Install vinyl corner posts at all inside and outside
corners. To allow for expansion and contraction, the corner
post is hung by placing a nail in the top of the uppermost
nailing slot. The balance of the nailing should be in the
center of the slots, 6 to 12 inches on center. This allows
expansion and contraction to occur at the bottom of the corner
post. Hanging the corner post also makes installation easier.
I've watched more than one contractor fight with a flopping
corner post as they struggled to nail it from the bottom
Corner posts are available in 10- and 20-foot lengths. I
always recommend using a one-piece corner post. Splices are
unsightly and if designed incorrectly, may allow rain to
After the corner posts are installed, measure down from the
chalk line snapped earlier, and snap another line that
represents the top edge of the starter strip. The starter strip
layout line is typically 2 inches above the bottom edge of the
first siding course, but the distance will vary depending on
the manufacturer. When installing the starter strip, leave
1/4-inch gaps between butting ends and at corner posts.
Running the Siding
Snap the first course of siding panels into the starter strip
and fasten them along the top flange with nails driven through
the center of the nailing slots. To allow for expansion and
contraction, draw the nails up just short of snug (see ""). Use
corrosion-resistant nails, with heads at least 5/16 inch in
diameter (roofing nails, for example). Stagger the end laps and
check alignment every five or six courses.
Always overlap panels so the exposed ends face away from
main entrances and high-traffic areas. The lap joints will be
much less noticeable as people approach the building.
Some installers will try to adjust the panel to an
out-of-level condition by pulling one side of a panel up
tighter than the other. Don't do this: Over-tensioned panels
can tear when they contract. On the other hand, if the fit is
too loose, the panel may work free from the locking hem as it
Consider this scenario: It's 10°F outside and you just
finished installing a 10-foot length of fascia on the west end
of a house. Next summer, when the temperatures hit the high 90s
and the sun-baked surface of the fascia reaches 120°F, that
10-foot length will have grown over 1/2 inch. If it can't
expand freely, buckling will result.
If the scenario is reversed, and you've installed a 12-foot
vinyl siding panel on the hottest day of the year, that panel
can shrink a full 1/2 inch when temperatures drop to 10°F.
The panel can tear apart if the shrinkage movement is
If it were up to me, I would require every vinyl siding crew
to spend five minutes at the beginning of each day chanting
this mantra: "expansion and contraction, expansion and
contraction, expansion and contraction...." This issue is
responsible for over 80% of the complaints I investigate.
Door and Window Detailing
Use J-channel around windows and doors to receive the siding
panels (Figures 4a & 4b).
Trimming a WindowFigure
4a. When trimming a window, first run J-channel around
all four sides, detailing the head piece as shown.Figure
4b. Place a notched piece of coil stock at each corner
of the sill to help direct water running down the J-channel
over the top of the siding beneath.
Dual Utility TrimFigure
5. Dual utility trim is used to secure panels that have
been notched around openings. Use the outer channel if the
notch ends at the thicker portion of the panel profile; use the
inner channel when the notch ends at the thinner panel
Use a snap-lock punch to punch barbs along the notched panel
edge before inserting it into the utility trim. The barbs will
hold the panel in place but allow the panel to expand and
contract. Use this detail to secure the cut edge of panels at
the soffit as well.