How To Install a Skylight

Skylights enhance the mood of just about any room in the house, even a bathroom. Properly located and installed, they shed a brilliant beam of sunshine on parts of the room that you want to highlight. Even on cloudy days, they bring suffused daylight into the room giving one a refreshing sense of the outdoors. On rainy days, the water hitting the skylight presents a pleasing patter or a raucous rattle depending on the storm’s intensity. Either way, the effect can be mesmerizing. Improperly located, skylights can illuminate spaces or things you would rather they didn’t and can even cast shadows in unwanted areas. They can also leak into the room during rains and collect annoying condensate, which may soak attic insulation, ruin ceiling sheetrock, and drip down into the room as well.

Skylights come in a wide array of interesting configurations. Squares, circles, rectangles, flat glass, domed plexiglass, polycarbonate, etched, or even stained glass all can be found in different skylight manufacturer’s inventories as well as the popular tubular style skylights or light tubes.

Installation preparation

Skylights are a beautiful complement to any room

1. Like real estate, location is everything in planning a skylight installation.
2. Decide how you want natural light to affect the interior of your room including the furnishings.
3. If you have access to the attic, crawl inside and look over the layout of the roof rafters and the ceiling joists. Some areas allow you to cut ceiling joists and roof rafters while others do not. Basically, you never want to cut any member of a roof rafter system or any chord of a roof truss if you can avoid it unless local building codes specifically approve it. In general, the same applies to ceiling joists.
4. Make certain that the location of your skylight does not interfere with wires, piping, ductwork, or mechanical equipment in the attic area.
5. If you have a flat built-up roof that is hot-mopped asphalt, torchdown, or polyurethane, you can simply layout the skylight and cut through the roof and the ceiling leaving you with a very small light shaft to finish off with sheetrock.
6. For regular pitched roofs, you will most likely have to frame out a light shaft between the roof opening and the ceiling opening. These light shafts can be of any design you choose, straight, splayed out, rectangular, square, round, oval, etc.
7. Mark the skylight location with nails driven through the roof. Make sure your layout takes roof rafters and ceiling joists into consideration.
8. Cut the opening with the proper saw, i.e., a circular saw or a reciprocating saw.
9. Tranfer the corners to the ceiling below.
10. In good weather, cut out the roof material.
11. If  your skylight has a built-in curb, you will not have to build a curb on your roof. If your skylight does not have a curb, build one to match the hole dimensions on the roof. You can frame your curb out of 2×6 dimensional lumber.
12. Your skylight may be the self-flashing type. If so, you will not need a curb for that style either.

Skylight installation

1. Place the skylight over the curb and fasten it with nails or screws.
2. If your skylight is the self-flashing type, simply slide the upper flashing beneath the roofing material being careful not to damage the felt or shingles.
3. Install the saddle and apron flashing around the sides, top, and bottom of the skylight. Use good flashing installation techniques and plenty of roof cement to seal any and all joints.
4. Frame in the skylight shaft.
5. Install the sheetrock in the light shaft. Mud, tape, sand, prime, and paint the light shaft walls to match your décor.

Tips

Follow all manufacturer’s instructions for self-flashing skylight installations and for skylights with built-in curbs.

Pay close attention to detail in placing the skylight on or in curbing and while installing all the flashing.

Make sure you seal all joints and flashing seams by soldering or using roof cement or caulk.

If you are unsure about working on your roof or about framing or installing your skylight, do not be afraid to seek the help of a qualified professional.