What kind of underlayment should I use?
It is recommended to use No. 15 asphalt-saturated underlayment for roofs with slopes of 4:12 or more. If your roof has a slope between 3:12 and 4:12, it is recommended to use a minimum of two layers of No. 15 underlayment. For heavy-weight shingles, you could use No. 30 underlayment instead.
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