Step 4: Attach the New Sill

Press the new sill into the adhesive, and immediately clamp it in place by driving 3½-inch deck screws through the plastic and into the wood. Stop when the heads are about ¼ inch below the sill surface. Immediately wipe up any adhesive that squeezes out. Fill any gaps between the old and new sill with adhesive.
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    Tools List

    • circular saw
      Circular saw
    • detail sander
    • drill
    • hammer
    • flat prybar
      Pry bar

    Shopping List

    1. 8d stainless-steel ring-shank nails
    for casing

    2. 3½-inch deck screws for sill

    3. Two-part acrylic adhesive (The brand used here is Bond&Fill.)4. Cellular-PVC windowsill (The brand used here is Kleer Lumber, which has the most sill options. AZEK also makes a PVC sill.)