1/4" 
1" 
1 pc. outside corner piece
flashing behind finished corner assembly
butted splice joint
CertainTeed Vinyl Siding Installation Guide
NOTE: If the transition material allows, the bottom 3/4" of the channels may be removed from the outside cornerpost so that the face of the corner may be positioned lower and more in line with the bottom of the siding. This method creates
a transition with more pleasing aesthetics. The outside cornerpost face must still maintain 3/8" or 5/8" clearance from obstructions.
If posts must be spliced for high walls, you have two options:
Option 1
Cut 1" off the nailing flanges and back so just the face of the outside cornerpost remains. Then lap 3/4" of the upper post over the lower post, allowing 1/4" gap for expansion. This method will provide an obvious joint between the two posts, but will allow water to flow over the joint, reducing the chance of water infiltration.
When the bottom edge of a cornerpost terminates into a porch, deck, brick, stone ledge, or roof line, etc., allow 3/8" for every 10' of corner when the ambient temperature is above 40°F; 1/2" for every 10' of corner when the ambient temperature is 40°F or below.
NOTE: It is acceptable to reverse lap outside corners as long as the corners are properly flashed and water can drain from the bottom of the cornerpost.
Option 2
Cut a 6" length of cornerpost and trim the nail flange, receiving channel, and sides until you have just a 90° bend of vinyl. Using PVC primer and PVC cement, glue the bent piece to the inside of the upper post and lower post. Butt the two posts together.
Nail the entire assembly as one post with all nails in the lower post centered in the nail slots.
Also see additional instructions covering installation of
splice backer (hidden)
PVC adhesive on backside of cornerposts
cornerpost
splice backer
PVC primer and PVC cement must be used
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