Adding Rafters?

The skylight we put in the bathroom wasn't too bad at all to do.
Current rafters are 20-22" apart (They vary) so our 15X30" skylight in the bathroom was framed in between 2 existing rafters.

In our stairway that has the roofline directly overhead, a rafter runs down just about the middle of the stairway. We'd like to add a 15X60" skylight here.

So, I thought I could just run 2 new rafters along the sides of the skylight similar to the bad picture below since we have relatively easy access to the roofline from top plate to ridge board.


Yes, the original rafters are a bit undersized by today's standards. Thankfully, the 12/12 slope has kept the snow loads down over the years. We can match the existing rafter size and still have enough strength for today's building code if we use LVL. No problem there.

But what do I do about the fact that there is no opposing rafters on the other side of the ridgeboard to take any load from the rafters? Do I need to add 2 more full rafters to the other side? Do I add 2 more short rafters to the other side that I header off to transfer load to other existing rafters? I don't want to end up w/ this:



My wife and I were just discussing the planning of this skylight last night, and I don't want to tell her we can do it for sure until I know I'm sure we can do it!

rafters

The ones on the other side will be intermediate to the new ones, so doubling/headering the ridge board across the area where you will remove the rafter and then attaching the new ones to it, will redistribute the load.

Not sure I understand what you're saying correctly. Are you saying framing the upper part like this will take care of it?

A little higher... so that you're basically sistering the ridge board, is what i think he meant.

rafters

It's a little bit of overengineering, but I would recommend simply doubling up all your blue-colored rafters (using brackets where appropriate) in your original picture.

Greg

I've always doubled up rafters around a skylight
Even when building my 3 season porch where the skylight fit between the rafters. For my sunroom the inspector even wanted hangers on the top & bottom framing for the skylight. These were also doubled up
I actually just checked the Velux online instructions
They show the top & bottom framing doubled up, but not the sides
Possibly if your are cutting more then one rafter you then need to double up the rafters?

Not the best picture, but it shows the framing

Scuba_Dave said:

For my sunroom the inspector even wanted hangers on the top & bottom framing for the skylight. These were also doubled up
I actually just checked the Velux online instructions
They show the top & bottom framing doubled up, but not the sides
Possibly if your are cutting more then one rafter you then need to double up the rafters?

Click to expand...

Yes, it depends on how many you take out. The hangers are standard.

Looking at that picture, I would be wondering whether they needed to be tripled... what's the spacing?

framing

Move the red line up to the ridge and extend the new blue rafters to it. you can also install a new jack rafter where the old one was to back up the load from the other side.