Replacing an old skylight can seem like a daunting task, but with the right techniques and safety tips, it becomes manageable. Skylights are a great way to bring natural light into your home, but over time, they can become problematic. Leaks, foggy glass, and non-operable windows are common issues that indicate it’s time for a replacement.
In this guide, we’ll walk you through the steps to replace an old skylight and ensure a watertight installation.
Identifying the Problem
The first step in replacing a skylight is identifying the problem. Common signs that your skylight needs replacing include water stains around the trim, peeling paint, warped wood, and foggy glass. Water stains and peeling paint indicate that water is getting through the trim, while warped wood suggests long-term water damage. Foggy glass typically means the seal on the insulated glass has broken, allowing moisture to get in.
Gathering Materials and Safety Gear
Before you start, gather all necessary materials and safety gear. You’ll need a new skylight unit, shingles, nails, a roof ladder, harnesses, roof jacks, a pry bar, a hammer, and self-sealing membrane. Safety is paramount when working on a roof, so ensure you have a roof ladder hooked into the ridge, harnesses tied into the ridge, and a secure plank on roof jacks to provide ample room to work.
Removing the Old Skylight
Begin by removing the shingles around the old skylight. Start from the top and work your way down, being careful not to damage the shingles as you’ll reuse them later. Use a pry bar to lift the shingles and remove the nails. It’s essential to remove at least two or three courses of shingles above the skylight and about a foot to the left and right to ensure there’s enough room to install the new flashing properly.
Next, carefully remove the old skylight. In most cases, skylights are nailed through the flange. Pry the nails loose and lift the skylight out of the opening. You may need assistance to safely remove and handle the old unit.
Preparing the New Skylight
With the old skylight removed, prepare the new skylight for installation. Modern skylights are often different in size from older models, so you may need to trim the inside of the opening to fit the new unit. Start by cutting and fitting extension pieces with a tapered rabbet to match the tapered dado on the new skylight. Slide these into place around the opening, then build off them with filler pieces and trim to ensure a snug fit.
Once the trim is prepared, assemble the new skylight by gluing and nailing the pieces together. This step ensures that the new skylight fits correctly into the existing opening, providing a watertight seal.
Flashing the Opening
Before installing the new skylight, flash the bottom of the opening with a self-sealing membrane. This step is crucial for preventing leaks. Apply the membrane along the bottom of the opening, ensuring it overlaps the top course of shingles. This overlap directs water away from the opening and prevents it from seeping under the shingles.
Installing the New Skylight
Now, you’re ready to install the new skylight. Carefully place the skylight into the opening, ensuring it sits on top of the first course of flashing. Secure the skylight by nailing it into the sheathing every six to eight inches. Once the skylight is secured, apply a second piece of self-sealing membrane on top of the first piece and up the front of the skylight. This additional layer provides extra protection against water infiltration.
Next, install the flashing kit that comes with the skylight. Start by nailing the bottom piece of flashing into the side of the window. Then, reinstall the shingles, ensuring they overlap the flashing correctly. When nailing the shingles, avoid nailing too close to the skylight to prevent lifting during windy conditions.
Step Flashing the Sides
For the sides of the skylight, use a step flashing technique. Begin by placing a piece of flashing over the shingle and the side of the skylight, then place a shingle on top of the flashing. Repeat this process, alternating pieces of flashing and shingles up the side of the skylight. This method ensures a watertight seal that prevents water from seeping behind the shingles.
Finishing Touches
Once the sides are flashed, apply a final strip of self-sealing membrane across the top of the skylight. This step covers any gaps between the membrane and the roof paper, providing a continuous barrier against water. Finally, install the counter flashing. Snap the counter flashing into the side of the skylight, ensuring it covers the top of the step flashing on the sides and the bottom flashing. Secure the counter flashing by rotating a small piece of metal into a slot and bending it down, locking it in place.
With the exterior work complete, check the interior trim around the skylight. Apply caulk around the perimeter of the trim to seal any gaps and prevent drafts. This step also gives a finished look to the installation, ensuring the skylight is both functional and aesthetically pleasing.
Replacing an old skylight requires careful planning, the right materials, and a focus on safety. By following these techniques and tips, you can successfully install a new skylight that enhances your home’s natural light while preventing leaks and other common issues. Remember, the key to a successful skylight installation is ensuring a watertight seal at every step, from removing the old unit to flashing and securing the new one. With patience and attention to detail, you can enjoy the benefits of a new skylight for years to come.
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