Where should ice and water membrane underlayment go?

Ice and Water Roof ProtectionRoof Ice & Water Membrane

The purpose of ice and water underlayment is to stop water from passing through the roof system into a home. Ice and water membrane is needed most to address ice damming issues during the winter.

Roof Ice Damming

Ice can build up on a roof slope, usually at the unheated area at the eaves, forming an ice dam that prevents water from draining off the roof. In turn, this water can creep up under the shingles causing a roof leak. Ice and water membrane must be installed far enough up the slope to cover the first few feet of heated space.

Installing Membrane Underlayment

Ice and water membrane should be installed at least six feet up the slope of the roof from the eaves, 6 feet wide in all valley areas, and around any heat source such as a skylight, chimneystack or flange. Ice and water membrane is a good investment and strongly recommended on roof rafters longer than twenty-five feet, on roof pitches below 4/12, and above cathedral ceilings.

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