22x23 ft hip joint ceiling

[Makoto]

Hey guys, so I've learned a lot and done a TON of research over the last couple years for this but I want to run this by the journal.

A short recap:

I have a maxjax in the garage 6 joists on the 8 ft top plate going across the garage. I moved one of them to give me more clearance for the lift but I need more room for trucks and I also need a ceiling for when I AC the space.

So, the space from wall to wall is 21.5x22.5. The ceiling joists/rafter ties used are garbage, cut too short and so they're effectively 2x4's spanning 21.5 ft. not good.

My solution is to replace all of those joists with 2x8's cut to the right angle and length on 16" centers for my 5/8 sheetrock/blown insulated ceiling.

I'm pretty sure that's kosher.

The thing I'm unsure about is for the sectioned area above the lift. I want a 8 ft wide 15" rise spanning the length of the garage down the middle.

Option 1: stack a 2x8 rafter tie on top of the ceiling joists each side of the lift cutout area then use 2x4's with 16" centers going all the way back

Option 2: 2x8's going across as rafter ties above the lift cutout and use 1x3's to screw my sheetrock/tie the rafter ties laterally together?

Option 3: same as option 1 but use 2x10's on top of the ceiling joists.

Also, in the meantime would it be okay to section that strongback to give me the clearance I need or should I only section it if I'm going to actually somehow tie each side together?

 

[rburke65]

Absolutely no idea from me, but others will chime in with ideas and still others will tell you to get an engineer. Good luck.

 

[kbs2244]

In Houston, this is a code issue, not a snow load.
Will they allow you to replace those full length joists with "collar joists" placed at the 1/3 point.

I don't recall ever seeing it done with a hip roof.

 

[Makoto]

In Houston, this is a code issue, not a snow load.
Will they allow you to replace those full length joists with "collar joists" placed at the 1/3 point.

I don't recall ever seeing it done with a hip roof.

I don't really care much about code. What concerns me is safety and quality. Its not up to code at this point anyhow so anything better than this will be a step up.

From what I've been able to dig up the only difference between a ceiling joist and a rafter tie (I think thats what you mean by collar joist) is that the ceiling joist sits on the top plate (generally).

Now, the collar tie is at the upper 1/3 and the joists are in the lower 1/3. From what I can tell anything that acts as a joist in the lower 1/3 is fair game. I'm certain its fine for the function of what rafter ties should be performing (keeping the building from fanning out), the part I'm most concerned with is whether or not my design will be fine for sheetrock and blown in insulation.

My quandry is regarding the raised portion in the middle for the lift.

Thanks for the replies keep it coming!

 

[Makoto]

bump!

 

[kbs2244]

In order for a collar joist to act as a tie for preventing wall spreading it needs to be in the lower 2/3 of the span.
The lower, the stronger.
So don't go any higher than you need.

Use the Simpsion style hangers at the joints.

 

[Makoto]

So here's a rough approximation of what I think I can do. add 2 2x8 ceiling joists sisted to the existing one on the middle, bridge the 8ft gap with 2x6's on 24' centers, and a couple joists on the other side holding. front to back 2x8x21.5" ceiling joists are on 16" centers and I'll be adding to the 6 joists already there (not shown).

the angle of the roof is a little too shallow so the drawing isn't perfectly to scale.

Thoughts or concerns? I think I can finish the ceiling and get a decent AC wall unit installed for under 2 grand if my math is right.

 

[Falcon67]

Personally, I don't see a problem with that.

>In Houston, this is a code issue, not a snow load.
Having lived in Houston, pretty much nobody gives a **** about codes and zoning. The quality of workmanship on many of the houses there is abysmal. And I don't mean cheap houses either.