FOR DOUBLE-HUNG WINDOWS USING FRAME ... - Pella.com

1 PREPARE THE OPENINGA. Prepare the rough opening. rough opening on both sides, the top and the bottom.Note: If installing new blocking, install the blocking so it’s flush with the exteriorsheathing of the house. DO NOT attempt to install a window in an undersized opening.B. Apply sill flashing tape #1. width. Apply at the bottom of the opening as shown. If the sheathing or water resistive water resistive barrier.Note: The tape is cut 12" longer than the width so that it will extend 6" up each sideof the opening.6"1B1"6"1B1/2"1/2"1CC. Tab the sill flashing tape and fold. barrier.Note: This step is not required if the exterior trim has not been removed.1"1F1DD. Apply sill flashing tape #2. E. Verify that the installation screws will fasten into solid wood. at screw locations.F. Install and level sill. center. Adjust shims as necessary to ensure the sill is level.