What kind of underlayment should I use?

No. 15 asphalt-saturated underlayment is recommended for roofs with slopes of 4:12 or more. Your contractor should use two layers of No. 15 underlayment for roofs with slopes between 3:12 and 4:12. If your contractor plans on using heavy-weight shingles, he could also use No. 30 underlayment instead.

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