Skylight Windows: How to Install New Skylights - DIY, Do It Yourself Home Improvement

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Skylight Windows: How to Install New Skylights

Written by kenny

Adding a skylight to your home can create an entirely different atmosphere to a room. Many times, people are leery of cutting holes in the roof; however, installing skylight windows is not as difficult as you might think.

Tools and Materials:

Skylight windows and flashing
1x2 cleats
Drywall
Level
Utility knife
Keyhole saw
Chalk line
Nails
Circular saw
Ladder
T-Bevel
Roofing cement
Framing for curb, roof, and ceiling headers
2x4s for light shaft
Rigid foam insulation
Steep tape measure
Pry bar
Hammer
Carpenter’s square
Plumb bob
Tin snips
Reciprocating saw
Try-square

Types of Skylight Windows

There are two basic types of skylight windows. These are: curb-mounted skylight windows and frame in place. A curb-mounted skylight window is raised above the plane of the roof. It will either set on a wood frame curb or the curb is part of the unit. This type of skylight window will be glazed with clear acrylic dome or glass. A framed-in-place skylight window is installed flush with the plane of the structure, just like a vertical window. This type of window is held in place with L-shaped brackets. It is glazed with glass. Both types can use insulating glass, and they can also have low emissivity coatings and argon gas fill for extra efficiency.

Skylight Windows Installation Step #1 – Framing the Rough Opening

Decide on an approximate location of your skylight. This is generally in the center of the room.
Locate the ceiling joists. Realign the opening so it will fit between the joists. You may need to cut the ceiling joists and rafters, depending on the size of your skylight window. Many skylight windows will fit between 16” and 24” on center joists and rafters without removing any framing.
Mark two corners of the ceiling opening that are closest to the outside wall. Be sure to make the points parallel to the wall. The ceiling opening width should match the rough opening width of the skylight. The length will vary and will depend on the type of light shaft you decide on.
At the marks, drill small holes and push two pieces of stiff wire up into the attic. This will help you locate this spot easily from above.
Go to attic with a 2’ by 4’ piece of plywood. Lay this plywood across the ceiling joists to help you prevent putting your foot through the ceiling. Locate the corners and clear the insulation away from the area. Remember to turn off the power if there are any electrical wires that need to be rerouted. Be sure to check that the power is off by using an electrical tester.
Use a plumb bob to help you locate the two points on the underside of the roof that are directly above the lower corners of the ceiling opening. Mark these points on the roof. Drive four nails up through the roof to mark the corners of the rough opening.
Remove shingles from around the opening. Allow room to install flashing.
Set chalk lines between the nails and cut away the roofing felt with a utility knife.
Cut away the sheathing with your circular saw. Remove it.
Framing the opening will depend on the size and position of your skylight window. For skylight windows that fit between two existing rafters, cut two headers to fit between the rafters. Nail them in place with 16d common nails. Flush with cut edges of sheathing.
If a rafter must be cut, nail two 2x4s across the rafters for temporary support. Make sure the 2x4s are long enough to reach two rafters on each side of the one that will be cut.
Use a reciprocating saw to cut the rafter out of the opening 3” from the edge of the sheathing on each side. Nail first pair flush against the two ends of the cut rafter. Use three 16d common nails through the existing rafters into the headers. Drive three more nails through the header and into the end of the cut rafter.
Nail the second pair of headers in place. Use 16d nails and nail through the existing rafters and headers. Use a pair of 8d nails every 16” to nail the two headers together.

Skylight Windows Installation Step #2 – Installing the Skylight Window

Curb Mounted Skylight Windows

Nail four 2x6s into a box. Square it. Nail it into place over the opening with 8d galvanized nails.
Run a bead of caulking all around the top of the curb. Set the skylight in place and fasten down.
Replace shingles. Allow enough working space between the edge of the shingles and the curb for the flashing.
Install sill flashing first. Nail into the curb.
Install side flashing and fasten it in place.
Go back to attic. Remove any temporary supports.

Framed-in-Place Skylight Windows

Mount brackets on the side of the skylight.
Set it in the hole and fasten it in place.
Make sure skylight is square and not twisted within the hole.
Install flashing.
Go to attic and remove any temporary supports.

Skylight Windows Installation Step #3 – Building Ceiling Opening and Light Shaft

Find two corners of the ceiling opening from inside the room. Use a square to ensure opening is square and use a keyhole saw to cut away the drywall. Go to attic. If ceiling joist needs cut, place temporary supports across the opening. Cut the joist 3” back from edge of drywall. If light shaft is flared, cut joist at the angle of the flare.

Install headers across ceiling opening. If no ceiling joists are cut, a single header will do. If ceiling joist has been removed, use double headers. Determine angle of rafters and ceiling joists with a T-level. Cut 2x4 studs for corners of light shaft. Angle on each end to fit flush against rafter and ceiling joists. Place studs 16” on center. Use corner studs as templates for the field studs across top and bottom opening. Nail 2x2 cleats to the inside edges of the corner studs. This will act as backing for the drywall. Nail rigid foam insulation over the outside of the light shaft from the attic. Finish the inside of the shaft with drywall.