Depending upon the design of your skylight, you need to follow a particular procedure for its installation. The two main types of skylights can be determined by the way their flashing and curb are built. Curb mounted skylights require a pre-built curb on the roof opening, while self flashing skylights have the curb built along with it. Both curb mounted and self flashing skylights follow similar steps for installation up to the point where the curb has to be flashed. Of course, as the former variety needs the curb to be ready on the roof, you need to construct a curb either by yourself or with the help of a professional skylight installer. While flashing the curb mounted skylight, using step flashing is enough, though preformed flashing is the ideal one. The flashing must overlap as much as the shingles do, and is fixed down over at least a rung of shingles. At the bottom of the curb, the flashing should overlap across the curb’s top and upon each side of its sides. To install the self flashing skylight, you simply need to fix it onto the roof, in a position that opens directly atop the sealant. Fasten it with screws or nails and on both sloping sides at the built-in flashing’s outer edge. The bottom of self flashing skylights is exposed on top of the shingles.