Installing Roof Felt and Ice and Water Shield
DIY Guide to Proper Felt Roofing Underlayment Installation
Aug 3, 2009
Felt roofing underlayment and ice and water shield are designed to prevent leaks during heavy rains and especially during the winter season, when ice builds up on roofs.
Installing felt paper and ice and water shield is a critical step in preparing roof sheathing for shingles. They give a roof an extra layer of protection against the ravages of heavy rains, but in perhaps a less obvious way, protect the home's attic and interior from ice and water damage during the winter months, especially in northern climates.
How to Install Ice and Water Shield and Felt Paper
- When preparing to install a new roof, first tear off all the existing roofing and inspect the roof sheathing, replacing any damaged or rotted boards.
- Install new drip edge across the eaves prior to installing the first course of ice and water shield.
- Ice and water shield comes in 3-foot rolls that contain 66 lineal feet of material. Roll out a course across the eave, making sure to overlap the leading edge of ice and water shield with the top of the drip edge.
- Roll out a second course (especially in northern climates), overlapping it at least 3 inches over top of the first course. Some codes only require 3 feet of ice and water shield, but the added expense of a second course is minimal compared with the extra protection it gives the roof.
- Roll out 3 feet of ice and water shield across any valleys, running 18 inches on either side of the valley.
- Be sure to run ice and water shield and felt at least 4 inches up any walls that intersect with roof edges. Pull siding and J-channel loose to get the material behind the finished wall. Siding will need to be loosened anyway to run 8x8 flashing cards when shingling.
- Do not use nails or staples to attach ice and water shield if at all possible. If installing in cold weather, it may be necessary to secure the material to the sheathing, but if this is so, use only the minimum necessary fasteners to do the job. In valleys, only use fasteners at the outside edges of the material. In moderate to hot weather, the material will easily stick as it is peeled away from the plastic backing. In fact, it is somewhat difficult to install in very hot weather, as the material tends to stick to everything, including itself and the installer's hands. In summer months, it is best to tackle this part of the roof job in the early morning or in the evening.
- Roof felt comes next. Like ice and water shield, felt paper comes in 3 foot rolls. There are two weights available, 15 pound and 30 pound. 30 pound felt is twice as thick and strong, and much more durable, and is highly recommended.
- Roll out the first course of felt above the ice and water shield, overlapping at least three inches and securing to the roof sheathing with T-50 staples (3/8 inch length is usually sufficient). Roofing nails will work as well, but take longer and create larger holes for potential leaks.
- Work up all the way to the ridge, overlapping each course the same way, then install drip edge up the gable. The gable drip edge should be installed after the ice and water shield and the felt in case water does get in from the side of the house. A drop of water that gets under the shingle would have a lesser chance of leaking into the house because it would roll off the drip edge onto the felt, rather than underneath it.
- The last course of felt can be rolled over the ridge onto the other side and stapled. The ridge vent can be cut out when the installer is ready to install the ridge shingles. Rolling the felt over the top and covering the vent hole in the meantime makes the ridge temporarily watertight.
- With the ice and water shield and the felt paper in place, the roof is ready to be shingled.
The copyright of the article Installing Roof Felt and Ice and Water Shield in Home Exteriors is owned by Jim Whitton. Permission to republish Installing Roof Felt and Ice and Water Shield in print or online must be granted by the author in writing.
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