| 摘要 |
A roofing underlayment includes a flexible sheet made of felt at least partially impregnated with a coating material. The sheet is provided with at least one ridge extending in a substantially longitudinal direction. The ridge projects upwardly from the sheet and is flexible such that the ridge is collapsible when a downward force is applied thereto. The ridge is defined by a portion of the sheet. A method for making the roof underlayment is also disclosed.
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