Installation Instructions

CertainTeed Vinyl Siding Installation Guide

Window Flashing

If installing a new window and ﬂashing, refer to the window

manufacturer’s instructions and ASTM E2112, Standard Practice

for Installation of Exterior Walls, Doors, and Skylights for the

proper ﬂashing installation method for the window type and wall

conﬁguration of the project.

The width of all ﬂashings is determined by the type of accessory

surrounding the window and where the ﬁnal complete course of

siding stops below the window (in the case of the ﬂashing under

the window). The ﬂashing should extend past the nail ﬂanges of

the accessory. The width of the ﬂashing under the window must

allow for the diversion of water.

Installing CertaFlash BA around a rectangular window

1. Make diagonal cuts in the weather-resistant barrier at the upper

corners of the top (head) of the rough opening. Gently lift and

tape the ﬂap temporarily in place.

2. Cut a piece of CertaFlash Flex ﬂashing for the bottom (sill) that

is 12" longer than the width of the rough opening. Remove the

backer from the ﬂashing and begin applying one end to the

jamb of the rough opening 6" above the sill. (NOTE: the tape

will extend over the exterior edge of the jamb.) Applying even

pressure to the tape with your hands, work your way down the

jamb, across the sill, and up the opposite jamb, ﬁnishing 6"

above the sill. Flex the overhanging tape down onto the wall,

covering the weather resistant barrier in weatherboards fashion,

again applying even pressure to ensure adhesion.

3. Before installing the window, apply a continuous bead of

sealant to the interior of the window’s mounting ﬂange. Install

the window according to the manufacturer’s instructions.

4. Cut two strips of CertaFlash BA for the sides (jambs) of the

window. Jamb ﬂashing tape should extend a minimum of 3"

above the top of the jambs of the window unit and a minimum

of 1" beyond the bottom ﬂashing tape installed in step #2,

covering the width of the previously installed ﬂashing at the

base. Slowly peel release paper off as you press the ﬂashing

in place. Ensure the ﬂashing covers all nails and mounting slots

on the window’s mounting ﬂange.

5. Cut BA ﬂashing for the top (head) of the opening so it will

extend beyond both ends of the jamb ﬂashing Ensure the

ﬂashing covers all nails and mounting slots on the window’s

mounting ﬂange.

6. Finally, lay weather resistant barrier over the head ﬂashing.

Apply CertaTape over both diagonal cuts.