Northwest Renovation Magazine

A Home Improvement Magazine

Thinking about turning your attic, bonus room, or loft area into a living space, but the lighting and ventilation are inadequate? Installing a roof window could be the solution. In this How-To we demonstrate how to install a VELUX® roof window.

Roof window(s) can be a cost effective alternative to building a dormer (a structure projecting through a sloping roof with a window set vertically) in an existing structure. Dormers can cost thousands of dollars depending on size and needs to meet building codes.

The photo left shows the raw framing for this installation.Your installation will have a different set of characteristics so plan ahead for framing placement. If egress is not a factor, place the height of the roof window between 6’ to 7’-3” (top) and try to allow for a clear view when standing or when seated.

Tip: Cut a piece of cardboard to the size of your roof window and move it around to find the best placement.

The newly installed roof window.

VELUX® roof windows come in two sizes: (M08) 30 5/8” X 55” and (S06) 44 3/4” X 46 3/4”.

The cost of the S06, which is installed here, is $750 (this price includes window and flashing kit only).

Roof windows satisfy egress requirements for emergency escape. This top-hinged window opens to a 45¼ angle giving accessibility to the outside. Check with your local building code for height requirements and other specs for egress ability. A permit is required when cutting any roof rafter. You do not want to lose the stability of the roof structure.

Tools needed for this how-to can be rented at your local rental yard. Do not try to install the roof window alone. Most of the work can be done from the inside. Check the information below for where to purchase.

This how-to was provide by By Thomas C. Janss (TJ) of Skyview Remodeling, Portland, OR.

Tools & Materials: Utility knife, flat pry bar, drill, 3/4”-1” wood drill bit, hammer, tape measure, level, circular saw (for framing), reciprocating saw, framing square, nails. Best to rent a pneumatic framing nailer, roofing nailer, compressor and hose.

Step 1
Upon receipt of your roof window inspect the product immediately for damage. Clean the glass and look for scratches or other imperfections. Due to the size and weight of the window, delivery is recommended. After all is well with your product and framing is finished, you’re ready to start the installation. Look over the documents that accompany the product. The first step is to remove the sash from the window frame (see instructions on how to remove the sash). Without the sash in place the window will be easier to manage.
Step 2
After the sash has been removed attach the brackets to each corner. Make sure the brackets are installed facing the right direction they fit in the pre-cut groove. The flat side of the bracket should face the top of the window (handle side).
Step 3
Drill a hole at all four corners. Use a 3/4”or 1” drill bit to start the main cut.
Step 4

Use the drill holes to start the cut with a reciprocating saw. Have a few blades available because you’ll probably bend a few blades as the roofing material is very abrasive. Change the blade if you have to push the saw hard to make the cut. Do not cut into the roof rafters. Have a helper ready to hold the roof piece when making the last cut.

Step 5

Use the reciprocating saw to clean up the cut to insure a proper fit for the window frame.

Step 6

Using a flat pry bar start to remove the roofing material four courses above the rough opening. Work your way down both sides of the opening. As you remove the roofing material keep track of the order. Take your time and don’t damage the underlayment below the shingles.

Installing Window
Step 7
After all the roofing materials have been removed roll back the felt paper to reveal the sheeting. Nail the old plywood or OSB sheeting to the new framing.
Step 8
Place the window frame in the rough opening and check for level. Use shims to level the frame.
Step 9
Next check for square. This step is important. Use a measuring tape to square the frame to check both sides until each measures equally. After the window frame is square attach the frame to the roof using the brackets. Check often for square. See the provided instructions for mounting to the roof. Check the frame again for square.
Installing Window
Step 10
Once the frame is screwed in place and is squared you’re ready to install the underlayment on the outside roof. Use VELUX¨ underlayment ZOZ 121 to provide an additional barrier to water and ice. This is a two-person job because the adhesive is very sticky. One person should be on the roof for this step. Be sure to apply safety ropes to protect against falling when working outside on the roof.

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