Underlayment (Roof)

Roofing terms · plain-language definition, with its source

Roofing terms · definition

The water-resistant layer between deck and shingles — felt or synthetic — that backstops the roof covering.

Source: Wikipedia — Roofing Underlayment

  • Valley

    The internal angle where two roof planes meet, channeling heavy water flow. A leak-prone area requiring careful flashing (open or closed…

  • TPO Membrane

    A single-ply thermoplastic membrane for low-slope roofs — heat-welded seams, reflective white surface, widely used today.

  • Wind Damage

    Lifted, creased, or torn-off shingles from high wind. Coverage hinges on the roof's wind rating and proper installation.

  • Tear-Off

    Complete removal of the old roof to the deck before re-roofing — allows deck inspection and a proper new system. The recommended approach…

  • Wind Rating

    The wind speed a shingle is tested to resist (e.g., 110/130 mph), dependent on shingle grade and correct nailing/starter detailing.

  • Tapered Insulation

    Insulation cut to build slope on a flat roof so water drains to the drains/scuppers instead of ponding.

  • Wood Shake / Shingle Roof

    Split (shake) or sawn (shingle) cedar roofing — a natural look with high maintenance and fire-rating considerations.

  • Synthetic Underlayment

    A woven polymer underlayment — lighter, stronger, and more slip- and tear-resistant than felt; the modern standard.

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