How to Replace a Flat Roof With Skylights

Remove the roof shingles from the roof in the desired location for the skylights with a prybar. Remove at least 3 feet of shingles from the surrounding skylight area so that workers do not step on the roofing material and damage it.

Sweep away any leftover debris from the cleared roof area with a broom.

Place the measuring tape on the roof. Measure out the length of the intended skylight. Mark the measurement's starting and ending points with a pencil. Remove the measuring tape from the rooftop. Draw a straight line with the pencil and straight edge from the starting to the ending point.

Repeat step 3 for the remaining three sides of the skylight measurement until there is a perfect rectangle or square shape drawn with the pencil, depending on the shape of the skylight .

Use a measuring tape to measure the same dimensions from steps 3 and 4 on all the 2-by-4 wood lengths. Mark the starting and ending points with a pencil. Cut all the 2-by-4 wood lengths with a power saw.

Cut the square or rectangle shape out of the roof with a power saw. Make sure that the saw's blade makes a perfect vertical cut into the roof.

Line the new skylight opening with four of the 2-by-4 wood lengths. Nail them into the roof with a nail gun and nails. Make sure that the wood lengths are flush with the rooftop so that no portion sticks out from the surface. This creates a frame for the large opening.

Nail the remaining four wood lengths on top of the flushed wood installation with a nail gun and nails. This portion creates the curb for the skylight.

Place flashing down around the perimeter of the curb. The flashing should look like a capital "L." The bottom portion should flare out from the curb and the top portion should be pressed against the wood curb to create a protective barrier above the joint where the curb meets the roof. This flashing prevents rain leaks.

Bend the top portion of the "L" flashing over the curb with your hands. Secure the flashing to the curb with nails and a nail gun. Nail the bottom portion of the flashing to the roof with nails and a nail gun.

Squeeze sealant onto the top of the curb and flashing combination. Make sure that the sealant covers the entire top portion of the curb.

Place the skylight carefully on top of the curb and sealant. Press down to affix the sealant to the skylight. Place the skylight's screws into their pre-drilled holes and fasten them with a power screwdriver.