Installing Skylights II Part 2 of 3

By Mark Clement Figure 1 Part 1 of this project focused on laying out and framing the skylight opening. Now it's time to focus on cutting the opening and installing the unit. Cut it out Before climbing to the roof, safety is the first priority. Make sure you know how to use your ladders properly and either install roof brackets and a walk board or tie-off with a proper safety harness — or both. I used roof brackets and a walk board on this project. They provided an excellent platform for staging tools and materials and created a barrier between me and the ground, a handy feature. Snap lines. From the inside, drive the four corner screws pre-set earlier (Part 1) up through the roof deck and shingles. Outside, snap lines between all the screws (Figure 1). Figure 2 Cut hole. The cut-out is a primo place for safety glasses. Between shingle granules and cutting nail shanks in half there's a lot of gnarly stuff flying around at very high speeds. Use a circular saw and a blade you're no longer fond of to cut through the shingles and roof decking (Figure 2). It goes without saying that you should stand outside the lines when you're cutting, but I'll say it anyway: Stand outside the lines when cutting. The roof decking is likely to fall inside in one large piece, especially if it's plywood, so make some provision for that. Either just let it fall to an area that can take the hit or cut it out in smaller sections that someone inside can handle as they come free. Work together on this so no one gets hurt. Good communication is key! Cut back shingles. Velux's instructions were a little lean when it came to technique on installing skylights in an existing roof system, so I had to make some on-site adaptations and detail a system that would look good on the inside — and stay dry on the outside. My solution was to dissect the roof system without tearing off every shingle. First, I needed some working room so I used my Roofmates Shingle Saw (the ultimate roofing tool; by the way; a circular saw would also work fine here) to get it. I cut the shingles back 2 inches from the hole on the sides and 3 inches on the top and bottom. This exposed the roof decking, so I could integrate bitumane membrane and the Velux flashing system. Figure 3 Prep the Skylight There are three things to do to prep the skylight for installation. Glass. First, remove the glass. This takes two people and pressing a few tabs and buttons in the skylight hardware but it is well worth the effort. Set the glass safely aside for later. Note: we placed a piece of drywall over the glass to further shield it from breakage. Figure 4 Tabs. Next, bend the mounting tabs back and clinch to the side of the skylight frame. Strip flashing. Part of the flashing comes installed on the unit. Unscrew it and set it aside. You'll have a few little aluminum screws hanging around from the various flashings. Tip: Keep them safely stored until needed by embedding them in a scrap of rigid foam insulation (Figure 3). Self-Adhesive Membrane Velux recommends a self-adhesive (bitumane) membrane be installed in all areas with severe weather. I work in such an area and didn't want to skip this step (though I have installed many skylights long before the existence of bitumane and none leaked). The membrane is part of the reason for cutting the shingles back from the opening. Tuck and peel. Starting at the bottom of the opening, I tucked 5-inch strips of Grace Ice & Water Shield under the shingles and on top of the asphalt paper. Going up each side, I tucked a piece under the shingles and over the bottom piece of membrane. When I reached the next layer of asphalt paper, I slid the Ice and Water Shield under it directly over the roof deck (Figure 4). Figure 5 At the top, I tucked a piece directly over the roof deck (and under the tar paper) (Figure 5), then folded it over the side pieces. Once the pieces were installed, I reached under the shingles and peeled the paper backing off, enabling the membrane to stick to the roof system. This was a bit infuriating, but it worked and I'm glad I did it. Take your time and be patient, because if water did manage get under the shingles and asphalt paper in the vicinity of the skylight, it would be caught by the membrane and have a way to flow out of the roof system. The last step is to slice diagonal slots in the paper and fold it back so you can install the skylight frame. Again, this is an extra layer of protection. The flashing should keep everything out, but having the extra membrane in there lets me sleep better at night. Mark Clement is a remodeler and author of The Carpenter's Notebook and The Kid's Carpenter's Workbook, Fun Family Projects! Find out more at www.TheCarpentersNotebook.com. RELATED ARTICLES: Installing Skylights I Installing Skylights III