Proper flashing detail is critical for any exterior wall assembly. Improper flashing and excessive caulking can force and trap water in the wall. The objective of flashing around doors, windows and other junctures is to keep water flowing "down and out" to the surface of the wall. Flashing shall be installed per International Building Code section 1405.3 "Flashing."
Flashing material should be made from a non-corrosive material. Flashing should run a minimum of 2" vertically up the wall and should be overlapped by the moisture barrier.
Siding must never rest on the horizontal surface of flashing. Siding material should be a minimum ¼" above the flashing, preventing any potential for water to wick into the wall. Siding should be a minimum of 1" above roof flashing at roof to wall junctures.
Caulk should be used only on vertical joints where siding materials meet doors, windows and corner boards. Caulk should also be applied at the bottom of window ledges or other protrusions to prevent any water flow off the window from entering the wall. A non-hardening caulk should be used that will expand and contract.
If you have any questions regarding this or any other topic, please call Shakertown toll free: 1-800-426-8970.
SHAKERTOWN 1992, Inc.
P.O. Box 400, 1200 Kerron Street.
Winlock, WA 98596
Shakertown is a registered trademark of Shakertown 1992, Inc.
All rights reserved. © July 2005