How to Cut a Ceiling Opening for a Skylight
Step-by-step instructions for cutting an opening in the ceiling to install a skylight.
The concept of a solar tube skylight is simple: to allow sunlight to enter through a clear domed "window" above the roof into a reflective tube and into a living space (Image 1).
Choose an appropriate location for the skylight in a room. This location might require adjustment when you get into the attic to fit the tube around the rafters.
With an electric drill and an 1/8" drill bit, drill a hole through the ceiling drywall. Use a wire hanger to poke through the drywall and through the insulation into the attic air space (Image 2).
Heade upstairs into the attic to locate the wire (you may want to bring an extra light to illuminate). It's also a good idea to lay down a sheet of plywood so you don’t put your weight directly on the ceiling (Image 3).
After locating the hanger, look for anything that can obstruct the tube, which has to fit between the attic floor joists and the roof rafters. Avoid all hip and valley rafters (Image 1), where two planes of the roof come together. You can angle the skylight to avoid these rafters. Also be careful to avoid any electrical wires or plumbing elements.
Using an electric drill, screw a 2-1/2" screw through the underside of the roof (Image 2). This will mark where to cut the hole for the skylight on the roof.
Take the flashing and the solar dome, the crayon, utility knife, reciprocating saw, caulking gun, roof sealant, tape measure and screws to the roof. On the roof, find the screw and place the flashing over it (Image 1).
Next, trace around the inside of the flashing with a lumber crayon.
With the utility knife, carefully cut the shingles 1/2" outside the line just drawn(Image 2).
Flip the flashing upside down, lay it on the roof and trace around the inner circumference.
Using a reciprocating saw, cut a 14" hole around the outside edge of this latest crayon mark (Image 3).
Caulk around the underside of the flashing with roof sealant (Image 1).
Center the flashing over the roof hole (Image 2), slipping the flashing at the top under the shingles, and leaving the flashing on the bottom to extend on top of the shingles below the flashing unit.
Fasten the flashing to the roof with screws. Coat the screw heads with roof sealant.
With a tape measure, measure from the roof to the attic floor (Image 1). This measurement is the total tube length. It might be helpful to have another person in the attic helping to measure.
With alluminum tape, tape around the seams of the top tube (Image 2) and secure the two parts with a couple of extra screws.
Drop the top tube through the flashing and turn it so that it lines up with the coat hanger in the ceiling drywall below the attic floor.
A light deflector redirects sunlight down through the tube. Insert the deflector so it faces south, the best direction to "catch" the most sunlight (Image 1).
Place the dome over the flashing (Image 2), and screw it into place. Be sure not to over-tighten it for fear of damaging the tube or the dome.
At the original "hanger" hole in the ceiling of the living space, use a compass to draw a circle the size of the solar tube (find exact dimensions in the installation instructions (Image 1).
Next, using a jab saw, cut to the edge of the circle and then cut along the outside of the line (Image 2).
After measuring for the exact distance from roof to attic floor/living room ceiling, attach the top and bottom tubes together. The extension tubes come in 2' pieces.
Using aluminum tape, tape and seal the seams of each tube. Using a brayer roller adhere the tape to the seams (Image 1) evenly.
Slide and attach the top tube to the bottom tube -- the tubes just nest together (Image 2). Make sure to adjust tube lengths to the correct length of the overall tube.
Secure the tube in place with drywall screws.
Once the bottom tube is in place, wrap the outside tube with 1/4" pile seal (Image 1). Pile seal creates an expansion joint giving the tube room to rise and fall slightly as it heats up. It also prevents bugs and debris from getting inside.
Insert the tube into the hole (Image 2). Adjust the angle of the bottom elbow so it fits the top hole. Use trial and error until the tube sections line up (Image 3).
Once the tube is in place, pull it back down and seal the last seam.
While on a ladder in the living space, pull the zip ties through the skylight, tuck them up into the ceiling and push the tube back up tinto the attic. Cinch the zip ties tightly, such that the tube diffuser sits flush with the ceiling. Secure the zip ties with four screws. Try not to over-tighten the screws or they could damage the ceiling or deform the tube.
Trim the zip ties so they’re flush.
Pull off the protective film coating from the skylight. You should have sunlight streaming into your living space.
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