Step 4: Level the window

Tom silva installing a window
Photo: David Carmack
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Place a 2-foot level on the windowsill, and note its high side. Then hold a 4-foot level against the window jamb on that side, and shift the sill left or right until the level shows the jamb is plumb. Tack a nail into the fin at the lower corner on the same side as the first nail.

Next, lay a 2-foot level on the sill, and adjust the free bottom corner up until the sill is leve. Tack the fin in this lower corner to the wall.

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    Tools List

    • hammer
      20-ounce hammer
    • two-foot level
      2-foot and 4-foot levels
    • tacker hammer
      Hammer-tacker,
      for stapling builder's felt
    • utility knife
      Utility knife
    • 16-foot tape measure
      Measuring tape
    • caulk gun
      Caulk gun
    • drill
      Optional: Drill-driver and 1 5/8-inch stainless screws,
      for attaching sill extender to bottom of narrow aluminum sill

    Shopping List

    1. WINDOW

    2. CAULK

    3. MINIMIALLY-EXPANDING FOAM INSULATION

    4. 15-POUND BUILDER'S FELT

    an alternative to membrane for flashing the rough opening



    5. WATERPROOF MEMBRANE

    6. METAL FLASHING

    7. FOAM INSULATION

    8. 1 1/2-INCH ROOFING NAILS

    for fastening nailing fins to the sheathing