Standard Method

ICE AND WATER SHIELD IS USUALLY INSTALLED DIRECTLY ONTO THE ROOF SHEATHING

AT THE EVES AND THE CONSECUTIVE LAYERS OF UNDERLAYMENT ARE APPLIED ABOVE

THE WATER SHIELD TO THE TOP OF THE ROOF. THE EVE FLASHING IS THEN SET ON TOP

OF THE SHIELD AT THE EVE LINE AND THE SHINGLES OR METAL ROOF IS THEN APPLIED.

Our Method

PHOTO TO THE LEFT: THE 501 UDL UNDERLAYMENT WAS APPLIED ALL THE

WAY TO THE EVE FIRST AND THE FLASHING WAS THEN INSTALLED ON TOP OF THE

UNDERLAYMENT. THE ICE AND WATER SHIELD WAS THEN APPLIED ON TOP OF THE

FLASHING AND TUCKED UNDER THE 2ND ROW OF UNDERLAYMENT AT THE TOP.

THERE ARE A COUPLE OF REASONS THAT WE HAVE ADOPTED THIS METHOD;

IF APPLIED AS DESCRIBED IN THE STANDARD METHOD, WATER FINDING ITS WAY

ONTO THE WATER SHIELD WILL RUN DOWN BEHIND THE FLASHING AND SOAK THE BOTTOM

EDGE OF THE ROOF SHEATHING AND WILL ALSO FORM ICICLES DOWN THE FASCIA BOARD,

PUTTING OUTWARD PRESSURE ON THE EDGE FLASHING.

ANOTHER PROBLEM ASSOCIATED WITH THAT METHOD IS THE WATER SHIELD HAS A

LIKELY POSSIBILTY OF NOT AQUIRING FULL ADHESION TO THE ROOF SHEATHING AND

WILL CONDENSATE WHERE IT SITS OVER THE WARM SIDE OF THE WALL LINE. WE HAVE

REMOVED UNBONDED WATER SHIELD AND FOUND THE PLYWOOD SOAKED FROM THIS.

HAVING THE WATER SHIELD APPLIED OVER A LAYER OF FELT OR 501 UDL, ALLOWS AIR

MOVEMENT BETWEEN THE SUBSTRATE AND THE UNDERLAYMENT; CONDENSATION IS THEN

PREVENTED. THIS BECOMES EVEN MORE CRITICAL IN PLACES LIKE VALLEYS OR CRICKETS.

IF YOU USE SYNTHETIC UNDERLAYMENT, YOU MUST CHECK THE COMPATIBILITY TO THE

WATER SHIELD.

ALTHOUGH THE CBJ DOES NOT REQUIRE WATER SHIELD TO BE INSTALLED AT THE EVE LINE

UNDER METAL ROOFS, IT SHOULD BE APPLIED BECAUSE WATER INFILTRATION CAN HAPPEN

JUST AS EASILY ON A METAL ROOF WITH ICE DAM FORMATION.