How to Install a Skylight

October 31, 2017



Installing A Skylight - Clera Windows + Doors

A skylight opens up your home’s design plan to the beauty of the open sky. It’s the perfect way to introduce more natural light into your space, creating a more spacious and bright environment. Where there is no exterior wall to install a window into, you can utilize your ceiling space for this purpose by installing a skylight window.

Before you go knocking a hole through your ceiling, you need to plan really well. Keeping the sun in mind, decide where you want to position your skylight as having a window versus having a skylight in the room offers different effects. For example, a window in a wall will capture low-angled rays of sun during the winter and limits the high-angle sun during the summer months. A skylight will do the opposite thus, using these two types of windows interchangeably in the same room would be a mistake.

Another thing to note while keeping the sun in mind is people often have the misconception that the sun is just a super bright light bulb glued to sky during the day and then disappears at night. So, if you fail to plan and consider the positioning of your home in correlation to where the sun starts out and where it ends up, you may end up with a room that’s overheated by the sun or one that only gets a diffused, dull light all day. Skylights on the south- or west-facing portion of the roof will collect direct sun—skylights facing north or east may not get any direct sunlight. Remember, any skylight that is positioned to receive direct sunlight can turn into a heat trap so you’ll need to plan ways to control the heat gain such as ensuring the skylight can open and allow ventilation. Some window companies have controlled shades or blinds for their skylights, it’s definitely something worth looking into.

Now that we have the technicalities in order, we can start preparing the installation materials:

  • Skylight
  • 2-by-4s for the frame
  • Drywall and finishing supplies for the ceiling
  • Roofing paper
  • Roofing nails
  • 16d galvanized nails
  • Step flashing
  • Continuous flashing


  • Circular saw
  • Hammer
  • Flat pry bar
  • Tin snips
  • Utility knife

These instructions are intended to give you an idea of what involved with installing a skylight and are not by all means applicable to all types of skylights. Some skylights require different methods of installation and in all cases you should have some degree of carpentry skills and knowledge of working with metal flashing and roofing paper otherwise, you’ll find yourself with a skylight that pours in rain water instead of natural light.

  1. Cut and frame the opening From the inside of the roof, drill a hole where you want the center of the skylight to be and then work on the roof to cut the opening with a circular saw. When you frame the opening, ensure that it is compliant with building codes and that the ends of the roof rafters are supported before cutting them. Install header joists perpendicular to the rest of the joists.

    If the skylight is mounted above an attic, you’ll also need to cut and frame a hole in the ceiling of the room below it, and frame a light shaft through the attic. In this case, if you’re not familiar with basic carpentry skills or you are installing a large skylight that will involves the removal of more than one roof rafter, it is highly recommended that you consult with professionals or have a professional come and finish the job.

    Just as a design tip, pick a generous size skylight. Some people think that a smaller window would cost less, that’s not necessarily true. The same materials and tools are needed whether or not the hole in your roof is being cut small or large. Have you ever went into a washroom and noticed a tiny skylight in the ceiling and thought, “what a tremendous amount of effort for so little outcome”? It happens. Make this project worth the effort and cost.

  2. Placing the skylight Using a utility knife and a straightedge, cut the roof shingles about 3 inches back from the opening on all four sides. Set the skylight in place, centered on the opening, and attach it to the roof with nails or screws.
  3. Installing the roofing paper Next you’ll be working with the roofing paper and cutting them about 8 inches wide in order to slip them under the shingles. Work them by installing them in this order: Bottom piece, sides, and then the top. What you’re trying to do is overlap the pieces down-roof with pieces that are up-roof so any run-off water will shed properly. The tricky part is sneaking the paper under the shingles so, this is where the flat pry bar would come in handy. Using the flat pry bar, lift all the roofing nails that get in the way.
  4. Install bottom & step flashing Install the bottom flashing, a single piece that wraps partway around the skylight and sits on top of the roof shingles. Drive roofing or flashing nails horizontally into the skylight, not vertically into the roof.

    Next, slip individual pieces of step flashing under the shingles. On each side, start at the bottom and work up. The step flashing pieces must overlap each other by 4 inches or so.

    The flashing pieces have to be attached to the skylight and not the roof.

  5. Install the solid flashing piecesIn the final step, you’ll be installing the solid flashing pieces. These pieces are designed to fit tightly onto the skylight and ensure that water cannot enter between the step flashing and the skylight. Attach the bottom piece first and then the side pieces. Install the top piece (called the head flashing) by slipping it under the roofing and attaching it to the skylight.

There you have it, the basic steps involved with installing a skylight. If at any point, this home project becomes more than you can handle or you experience unforeseen issues along the way, contact a professional window installer in your area to help you get the job done right. A DIY project can save you money and help you gain experience but remember, the most expensive project is one you have to pay for twice. If you find yourself unsure about the installation process, there’s nothing wrong with asking for a little help especially for such an important home project.

Related Articles