Placement of the Skylight
Step1
Decide the size of your skylight and the thickness of the roof. If you have a skylight that will have a long light shaft, you might wish to make the light shaft wider at the bottom to allow for more light.
Step2
Make marks where you wish to place the skylight in your attic ceiling, driving a 16d nail where each of the four corners will be, and a fifth nail to mark where the skylight will open. Try to place the skylight where it will not interfere with the ceiling joists. You should be able to use two of the ceiling joists along the two sides of the skylight you will be adding to your attic.
Step3
Clear away anything within the 5 nails, such as insulation, to determine whether there are any pipes, wires or ducts within the space where you wish to add a skylight to the attic. Check the roof's underside as well.
Step4
Move the proposed placement of the skylight if you see something structural crossing the space such as a roof ridge or a structural member. Never cut trusses, but choose a skylight that will fit between them, even if it means you must choose a skylight smaller than you originally planned.
Step5
Transfer the mark of the opening (marked by a nail) through the roof using a plumb bob. Try to run one edge of the skylight you are adding to an attic along a rafter.
Step6
Drill holes at each of the 5 nails up through the roof so you can see them from the other side.
Cut the Roof
Step1
Use circular saw to cut wood shingles or shakes when you wish to add a skylight to an attic.
Step2
Choose a combination blade to cut wood shingles.
Step3
Use a carbide-tipped blade for cutting asphalt shingles.
Cut the Rafters
Step1
Mark the rafter if you need to cut it, and use a combination square or even an adjustable T-bevel to determine the angle at which it should be cut. Mark where the headers will fall as well.
Step2
Support the rafters for the skylight you will be adding to the attic with 2-by-4 inch lumber that's nailed to the existing rafters in the attic. You will remove them after installing the headers for the skylight.
Step3
Use a reciprocating saw to cut the rafters to create the opening where you are adding a skylight in the attic.
Install the Headers
Step1
Measure between the rafters to determine the distance. Use lumber that matches that of the rafters.
Step2
Cut 4 lengths of lumber to the specific measurements, and double each piece so you will have 8 pieces of lumber in all.
Step3
Hammer 2 nails in the ends, then hammer in the rest of the nails at 6-inch intervals.
Step4
Use framing anchor nails to fasten the joist hanger to the rafter, then use 16d nails to secure the header to the joist hanger. Use 8d nails to toenail the headers to the rafter.
Install the Skylight
Step1
Place sheathing around the entire of the rough opening, then cover that with roofing felt. You can add pieces of felt if needed when you add a skylight to an attic.
Step2
Spread roofing cement with a putty knife in a 4-inch-wide band around the opening, and make the layer of roofing cement ¼ of an inch deep.
Step3
Line the skylight over the opening you cut in the roof, and gently press on the flange into the layer of roofing cement. The bottom of the flange should rest on top of the shingles.
Step4
Use the fastener that the manufacturer recommends to secure the skylight you are adding to the attic in place.
Step5
Put more roofing cement on the outside of the flange to make it all the more waterproof. Make sure you cover the screws.
Step6
Attach new shingles all around the skylight you are adding to the attic.
