Velux Skylight Installation Instructions

Decide where the skylight is to be installed. Place the Velux skylight on the ground and measure its height and width using a tape measure. From inside the attic, draw a rectangle the height and width of the skylight on the rafters, where the skylight is to be installed. Cut away any battens inside the rectangle with a hacksaw.

Assemble scaffolding to access the roof. Remove tiles from the area where the skylight is to be placed using a pry bar to lift the tiles up and slide them out. Cut the underfelt away in the area of the skylight plus 12 inches on either side and 18 inches above and below the skylight. Cut through the chalk marks on the rafters that you made earlier using the hacksaw.

Screw 1/2-inch-wide battens around the perimeter of the rectangle using a hammer drill. Align the skylight over the opening using the alignment notches on the base to line the skylight up with the battens. Nail the skylight to the battens through the pre-punched holes in the mounting flange using a hammer and 1 1/4-inch carbon steel nails. Use one nail in each pre-punched hole for a secure fitting.

Remove the cladding from around the outside of the skylight. Roll out the Velux adhesive skylight underlayment along the bottom of the skylight plus 6 inches on either side. Cut the corners diagonally as with the side underlayments, and bend the underlayment so it covers the bottom of the skylight as well as the roof. Lift the rubber gasket and tuck the underlayment underneath it.

Roll out the Velux adhesive skylight underlayment along the left side of the skylight plus 6 inches on the top and bottom. Fold the underlayment so it runs along the rooftop and the side of the skylight. Cut the underlayment diagonally with a knife and fold it around the top and bottom of the skylight to keep a watertight corner. Repeat for the right side.

Lay underlayment over the top of the skylight with 6 inches extra above and on either side. Cut the rectangle of the skylight out so the underlayment can lie flat. Lift the underfelt above the skylight. Slide another strip of underlayment as wide as the skylight plus 6 inches on either side three inches under the underfelt so it overlaps onto the underlayment above the skylight. Again, cut out the skylight so it lies flat.

Cut a 1-foot-wide strip of lead flashing as wide as the skylight plus 6 inches. Lay it below the skylight with a fold up along the base of the skylight. Tuck the bottom of the flashing under the underfelt. Lay flashing along the top and down both sides of the skylight with folds up against the edges of the skylight. Replace the tiles, covering the lead flashing.