Doors and Windows - skylight installation removing roofing

I'm getting ready to install a small skylight on a 16 degree roof, appx 22 1/2 square. its a velux self flashing unit. Couple of quick questions. i saw a video on the internet where they just cut the rough openinng right through the asphalt roof shingles. They don't remove any shingles first. Seems like it would work, then lift up the edges and slide the rubber flashing under the shingles?

secondly do you put any adhesive caulk on the underside of shingles that rest on rubber flashing.?

If I can't talk you out of the skylight, I'll try to help you get it installed. 16 degrees is really shallow, and may puddle water around the unit and cause leaking. BUT that's your choice. IMO remove the shingles first in the area you will be installing the unit. You will have to pull up the stubs to install the light anyway, so why not do it right. Then you can reinstall the shingles from the bottom up, cutting as you need around the light. Yes, it is always advisable to put a little dollop of Henry's fiber roofing tar under each tab to keep it down, since you have separated the original tab from its seat.

its the wifes idea and I can't talk her out of it. Inside is still unfinished and easily accessible. Roof pitch is easy to walk on and on a first floor. If you could answer a question about underlayment. Since I'm going to lose several inches adjacent to the light when I make my cuts should I replace this with that self adhesive type in a square all the way around tucking it under the shingles? If so in what order and would you just overlap the corners?

What happened to your Velux installation instructions?
Anything on a roof can leak--skylights are the best at it.
Have fun..............................

Velux is the best, and their instructions are very clear. I don't cut out the roof under a skylight I am installing until I first remove the shingles. That is definitely slower, but I think it is more reliable. I have never had a roof leak because of something I did wrong.

Back in the 50's we were doing commercial skylights--we got into residential ( b/4 Velux) we got out faster than a cat on a hot tin roof--nuttin but leakers.................

Howard, I've got their instructions but everyone has a differnet way of doing it. Some guys cut from the inside. some from the outside. some use roofing cement. some don't. Just trying to get differnt opinions before i'm on the roof. appreciate the wisdom here.

With your shallow roof, anything you can do to help prevent water infiltration will be a plus, because you've got a train wreck waiting to happen. Make your location between joists if possible, remove the shingles in the area, cut from the outside, seal with tar, roof adhesive strips, etc. lay in the skylight, fasten it, shingle around it.