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Question DetailsAsked on 4/16/2013

roofing felt paper

what weight do I need to use

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3 Answers


Industry standard is 30 pound especially under wood roofs. Remember the ice shield on the overhangs and valleys if it freezes where you live.

Jim Casper

ps for info on gutters and covers for gutters see my blogs


Answered 7 years ago by jccasper


Most roofers now use a hitech roofing guard or like tri-flex 30. The 10 sq. rolls are much lighter and cover faster than felt. It also doesn't tear like felt and is about the same price.


Answered 7 years ago by RooferRick


30 pound is standard, but you can check what your lumber yard carries - they are usually pretty good about carrying what your local building code requires.

The felt is designed to protect against any minor leaks due to damage to shingles, or one-time backing up of wster under the shingles, so in general it never has to actually do its waterproofing job. If you really want it to work right, remember to overlay each width OVER the one downhill of it, so any water runs off each width and onto the one downhill of it, rather than under the lip of the sheet below it. To protect against backing up of water from ice damming high up on the roof (say because of rain on snowpack, that can block downhill flow under the snow), you can use bitumastic roofing caulk at each seam to prevent any backup from getting under the felt.

The most important thing, particularly if you are in snow country, is the ice and water shield. Check you local code requirements, but in snow country it is usually required for the lower 5 or 6 feet of the roof, because that is where ice damming is most common. One thing I like to see (here in heavy snow country), especially where the kitchen, furnace, and bathroom vents all more or less line up up and down the roof, is use of ice and water shield from the top stack or vent all the way down to the roof edge and extending 3 feet either side of the vents. That way any icing caused by warm air coming out of the vents (especially low to roof vents like typical kitchen and bathroom fan vents) cannot back up and saturate the felt. A cheaper alternative, or if your vents are scattered all over the roof, is to use a width of ice and water shield running up and down roof, centered sideways on the vent (in addition to and overlying the felt), running from about 2 feet above the vent to about 6 feet downslope (below where meltout icing from the vent occurs), and tailing out on TOP of a row of shingles, so any water that it traps around the vent runs out onto the shingles rather than under.

Answered 7 years ago by LCD

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