Installation Instructions
CertainTeed Vinyl Siding Installation Guide
76
Install panel
If necessary to maintain the slope angle, install furring under the sill 
as described on pages 31 to 32. 
NOTE: You can eliminate this step by using dual undersill trim. 
This trim has two receiving channels. Use the inner channel 
if you’ve cut the siding panel near the locking edge. Use the 
outer channel if the cut has been made near the butt edge.
Use a snap lock punch to raise tab faces on the outside of the 
panel. Punch out a tab every 6".
Push the horizontal edge of the cut into utility trim. Slide vertical 
edges of cut into J-channels at window sides. Make certain the 
installed panel locks into the panel below.
Fitting over windows and doors
The procedure for cutting panels for installation over windows and 
doors is similar to that explained earlier.
If necessary to maintain the slope angle, install furring above the 
window or door as explained on pages 31 to 32. 
Drop the panel into position, making certain it fits into the undersill 
trim and J-channel at the top and J-channel at the sides. Interlock 
the panel with the siding panels below.
Fitting at narrow openings between windows
To simplify installation in areas such as that shown in the 
illustration, install J-channel on both sides of opening. 
Bow the panel toward you and slip it into the channel.
If the area is very narrow, leave one J-channel unnailed except at 
the lowest point (as shown). Bend this channel out slightly to insert 
panel. When the panel is in place and nailed, nail the J-channel 
immediately above the panel and repeat the procedure. Be sure to  
leave adequate tolerances for expansion and contraction.
window
J-channel
utility trim
horizontal 
siding
dual 
undersill 
trim
installing trimmed panels 
with dual undersill trim










