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Installing A Skylight - Guidelines For Proper Skylight Installation

The information in this article is not meant to be a step by step guide for installing a skylight. It is meant to give you an overview of the processes involved.

We All Love Natural Light
Skylights are a great source of natural lighting. Generally, skylights can be installed in any room of a single story house or the upper most rooms of a muti-story house. Since installing skylights often results in making a small structural modification in the frame, a permit may be required before beginning construction.

The Perfect Skylight for Your Home
Before installing a skylight, you should determine the type of roof framing system in your home. Generally, skylights can be installed in both truss roof frames and conventional roof frames. However, you will be limited to size constraints if you have a truss roof frame. The size of your skylight should fit between the rafters of a truss roof frame. The rafters can be cut and re-framed to accomodate the skylight if you have a conventional roof frame.

Where to Put It
First determine the location in the ceiling where the skylight will be installed. Determine if there are any obstacles that might obstruct the skylight, (i.e. water heaters, heat and A/C units, plumbing, electrical wires, ducts). If so, either select a different location for the skylight or re-route the obstacle. Mark the ceiling accordingly to the size of the light (or shaft) and remove the ceiling drywall, and insulation. Next, cut the joist and frame the ceiling opening with the same size lumber as the joist. If your ceiling is a cathedral ceiling you will have to cut the roof opening in this step also.

Making the Hole for Your Skylight
Find the area in the roof you will cut open by hanging a plumb bob so that it falls into the center of the hole you cut in the ceiling. Unless your shaft is a flared shaft duplicate the cut in the roof and frame the opening. This creates a straight shaft. If your shaft is flared cut the hole in the roof accordingly to the size of the skylight.

You May Need a Shaft if You Have an Attic
If your ceiling has an attic space you should construct a shaft. You will need to install a shaft to divert the light into the room. Most ceilings, except cathedral ceilings, will require a shaft that connect from the roof to the ceiling. The shaft can be framed with 2X4 inch lumber, except in cases where the distance will allow you to nail plywood directly from the rafters to the ceiling joist. If the shaft frame is 3½ feet or longer it is recommended that you insulate the shaft and nail 4 or 6 mil polyureathene plastic to the interior of the shaft. The plastic will act as a vapor barrier.

Just Follow Instructions
Install the skylight according to the manufacturer's instructions. Failure to follow the manufacturer's instructions closely may result in a leaky skylight. Pay special attention to the flashing requirements.

Need more information on installing a skylight? Head over to our Doors and Windows forum and talk to others about your DIY project!