Attic Modification - What's the Best Approach?

[moparfreak]

So I've got an interesting little project coming up.

When I built my shop onto what was an existing 2-car attached garage, I structured the area above the new shop to serve as an attic. I put OSB sheeting up there to serve as floorboards and it's been real useful to have this attic space for all kinds of things. The one challenge has been that the area that is above the original 2-car garage (still part of the shop) is very difficult to access. This is because the original roof rafters of the house (a hip roof style in that area) allow for only 16" between centers, so putting materials through that opening is difficult, not to mention for me to crawl and squeeze in there also.

Now that I am getting ready to do a full restoration of my Charger, I want to use the attic as a space to put parts from the car as I pull them off so that the main shop doesn't get overrun.

I need to make a pathway, and I'm wondering, from a framing perspective, what's the best way to patch in an opening? If I cut out these two rafters will it cause issues with the original ridge of the house? I can probably do some sort of boxed in frame to get the load from the cut-out rafters transferred over to the outside ones.

Here's a picture to help explain (sorry about the junk blocking some of it). The red line is the pass-through opening I'd like to create. The yellow arrows point to areas that I could sawzall out and then try to reinforce the opening.

ALso, to help understand from an aerial view, this is the attic space as shown on the plans for the shop remodel. THe red lines are approximately the rafters I want to cut out:

If I cut those rafters out partially to make the passthrough, will it weaken any other part of the structure overall? I can't imagine it really would, since there's so much other framing tying the ridges together. Just want to make sure my thinking on this isn't way off base before I start hacking things up...

 

[matt_i]

Maybe I am confused but the 14" LVL ridge beams that run, roughly, down the center of your drawing, seem to be the highest point of the roof.

To meet up with those, it looks to me like the rafters that go to the valley (diagonal) should be 90 degrees to the red and yellow lines you have drawn-in.

If they don't, I'm having trouble visualizing where the ridge that they connect to, would be.

 

[FordTruckWench]

This is because the original roof rafters of the house (a hip roof style in that area) allow for only 16" between centers, so putting materials through that opening is difficult, not to mention for me to crawl and squeeze in there also.

The question is how the new roof in that area was framed. (The area being above the old garage where the roof plane needed to be extended up to the 14" LVL RIDGE BEAM.) Did they add new rafters from the ridge all the way to the exterior wall, or did they run only as far as the old roof?

There is the possibility that the old rafters "push" against the old diagonal ridge beam thus countering the load caused by other parts of the old roof. As such, you could pretend they are a wall and put in a header to make a larger opening.

 

[moparfreak]

Maybe I am confused but the 14" LVL ridge beams that run, roughly, down the center of your drawing, seem to be the highest point of the roof.

To meet up with those, it looks to me like the rafters that go to the valley (diagonal) should be 90 degrees to the red and yellow lines you have drawn-in.

If they don't, I'm having trouble visualizing where the ridge that they connect to, would be.

Sorry, it is a bit confusing. The new ridge (formed by the 14" LVL) was constructed 90 degrees to the existing house ridge, so yes those rafters are going the other way, you can see them in the upper right hand corner of the picture.

The rafters I propose to cut into are actually the rafters that support a part of the tail end of the original hip roof ridge. Here's a sketch over a pic during the demolition phase before framing started. You can actually see the same roof vent in the picture. I tried to sketch over it to show.

 

[moparfreak]

The question is how the new roof in that area was framed. (The area being above the old garage where the roof plane needed to be extended up to the 14" LVL RIDGE BEAM.) Did they add new rafters from the ridge all the way to the exterior wall, or did they run only as far as the old roof?

There is the possibility that the old rafters "push" against the old diagonal ridge beam thus countering the load caused by other parts of the old roof. As such, you could pretend they are a wall and put in a header to make a larger opening.

The new framing is basically a projected gable that intersects w/ the old hip ridge. I've sketched the way the new rafters look from the inside, going perpendicular to the ridge and connecting parallel and in plane with the diagonal hip ridge beam trailing down to the end of the house so that in looking head-on you basically don't even see the new gable on the back.

With the original hip ridge beam basically ******* into the new main perpendicular 14" LVL ridge beam I can't imaging taking a couple of the old rafters out would affect structure...but just trying to sound this out to make sure I'm not crazy here.

 

[FordTruckWench]

The new framing is basically a projected gable that intersects w/ the old hip ridge. I've sketched the way the new rafters look from the inside, going perpendicular to the ridge and connecting parallel and in plane with the diagonal hip ridge beam trailing down to the end of the house ...

Was afraid of that. That means the old (now buried) hip ridge is still carrying load. That ridge is likely not sized to carry the load all by itself, hence some of that load finds its way down via the old "defunct" rafters. Whoever drew your plan expected that load as evidenced by the 3-PLY 9 1/2" LVL HEADER, though that does also support the ceiling joists in the old portion.

 

[moparfreak]

Was afraid of that. That means the old (now buried) hip ridge is still carrying load. That ridge is likely not sized to carry the load all by itself, hence some of that load finds its way down via the old "defunct" rafters. Whoever drew your plan expected that load as evidenced by the 3-PLY 9 1/2" LVL HEADER, though that does also support the ceiling joists in the old portion.

OK I follow. If I were to cut those rafters, could I box the opening up w/ more 2x12s to maintain an equivalent amount of support, so as not to disrupt the load path down to that header?

 

[Radix2]

Double up your rafters on either side, put a header in to pick up the cut-off rafters, no different than cutting an opening for a stairway in a floor.

 

[moparfreak]

Double up your rafters on either side, put a header in to pick up the cut-off rafters, no different than cutting an opening for a stairway in a floor.

Well it's complete and pretty much did exactly that. Aside from the confined space to work in, it all went pretty well. Seems as solid as it was before certainly. Those rafters are only 2x6 original.

 

[Slednut]

When I started taking apart my present project car I bought a Whalen rack from Costco. If I had two I think all the stuff would fit on the racks except the Fenders, doors, hood and trunk lid.

IMO putting stuff in the attic would be a pain.

BTW I did almost the same to my attached garage.