How To Install A Skylight

Follow our 8-step guide below to install a skylight yourself.

Step 1. Cut The Opening

Drive a deck screw up through the roof at each corner of the rough opening from below.
Strip the shingles on the roof about 7 inches beyond those points.
Snap a chalk line between each pair of screws following the stripping.
With a circular saw, plunge-cut through the sheathing along the chalk lines on three sides.
Remember to stay off the cutout.

Step 2. Flash The Sill

Have a partner nearby for this step of the process.
Have the helper lower the cutout as you begin cutting the fourth side.
Place a strip of self-adhesive membrane across the bottom edge of the opening.
Cut and fold the top inch of the strip over and onto the exposed sill.

Step 3. Position The Skylight

Have the helper standing inside with the skylight, lift it up through the opening.
Rest the bottom edge against the sill, lowering it onto the roof.
Drive 1 and 1/4-inch galvanized roofing nails through the holes in the skylight’s flange and onto the roof.

Step 4. Seal The Sides

Cover the bottom flange with a strip of membrane, extending at least 6 inches beyond the skylight’s sides.
Cut these extensions at a 45-degree angle outward from both skylight corners.
Wrap the top part around the skylight frame and press the other part against the roof.
Cover the side flanges.
Now cover the top the exact same way.

Step 5. Sill-Flash The Bottom Edge

Nail the shingles over the bottom membrane.
The membrane should then seal around the nails.
Place the U-shaped sill flashing over the shingles, slipping it over the bottom end of the skylight.
Nail this piece to the roof, at the top outside corners of the U.
Cover the exposed sides with the shingles.

Step 6. Step-Flash The Sides

Overlap the top half of the shingles which cover the sill flashing with a piece of step flashing in an L shape.
Drive one nail near the top outside corner and another nail a few inches below.
Cover the flashing with a shingle, adding the next piece of flashing on top of that.
Do this on both sides of the skylight.

Step 7. Counterflash The Sides

Use strips of counterflashing to cover the vertical legs of the step flashing.
They should snap right onto the skylight’s rim.
Counterflashing is installed to seal out any inclement weather conditions like snow or rain.

Step 8. Install Saddle Flashing

The first course of shingles must be lifted above the skylight, slitting the underlayment.
Slip the saddle flashing’s top edge upward through the slit.
Fit the flashing against the skylight, lifting the shingles and nailing the flashing at its top corners.
Nail one last course of shingles over the flashing.
Try to leave 4 inches of the flashing exposed.

Skylight Installation In Phoenix

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