Raising Ceiling Joists - 1 Bay only

[ToddMcF2002]

Hi folks I have a 2 car attached garage with. 10” ceiling and I’m looking to raise the ceiling joists on the bay closest to the house. The other bay has a hip roof slope so I’m planning on leaving it be. The joists thankfully run front to back so I can alter one bay and leave the 2nd bay joists where they are. Since I’m leaving those joists intact to support the walls and the other side is attached to the house I’m guessing raising the other ones even 50% up (4 feet) won’t be an issue? I have a contractor coming in to consult but I thought I’d ask here as well.

This is my garage to help clarify. There is no room above the garage obviously. Just joists running front to back.

 

[GMCGarage]

Hi folks I have a 2 car attached garage with. 10” ceiling and I’m looking to raise the ceiling joists on the bay closest to the house. The other bay has a hip roof slope so I’m planning on leaving it be. The joists thankfully run front to back so I can alter one bay and leave the 2nd bay joists where they are. Since I’m leaving those joists intact to support the walls and the other side is attached to the house I’m guessing raising the other ones even 50% up (4 feet) won’t be an issue? I have a contractor coming in to consult but I thought I’d ask here as well.

Should not be an issue if the engineering checks out.

 

[mike93lx]

You want an engineer, not just a contractor. Let's the contractor do the work that the engineer specifies.

No one here will be able to tell you anything definitive, especially with the lack of details on the construction

 

[Falcon67]

Been there, just did that - no engineers were harmed (or contacted) in the process.

 

[ToddMcF2002]

I like what you did there! My peak is a bit higher so I can still get 13-14' and have joists. Regarding the engineering common sense should apply. I can truss the structure and add a cross beam. My contractor built a sizable addition in my last house so if says its good in my opinion its good. I like to sub my jobs where I can. Saves thousands. My last estimate for the garage has a $7800 electrical budget that I just subbed for $1650

 

[Falcon67]

The cost of the above was about 5 2x6s and about 8 sheets of OSB. Just about all material removed from the ceiling was reused. I moved one 2x12 east to make the Howe type truss deal, because it works for long spans. It sits over part of the door beam, but doesn't really change the loading. Part of the other 2x12s that came out were used to box the front end of the opening and as load spreaders across the back wall. It's boxed in about 20" from the front of the shop, mostly to give a place for all the electrical to run.

The max ground clearance is going to have more to do with the depth of the space, the roof pitch and existing wall height, rather than the peak. Your 10' ceiling gives you a big leg up. I have 23' 4" inside with 8' walls and a 5:12 pitch. So the "peak" is 13'. But in reality, I can just get the car high enough to walk under. The lift is 11' 8" from the door, 16' race car backed in, trunk lid is the limiter on the back side. I killed a lot of graph paper and made a lot of measurements, making sure I knew how much clearance and where the pinch point(s) were before picking up a tool.

Start here, at post #405
https://www.garagejournal.com/forum/showthread.php?t=100482&page=21

NOTE - and a warning. I made sure the upper collar ties were in the accepted collar tie range of the rafters. They are really only there to support the ceiling material, not the least bit structural. Merely raising joists in the lower 1/3 of the rafter increases the loading on the rafters, requiring they be upsized from normal specs. Keep that in mind as you go about your planning.

 

[firebirdparts]

How much height do you want? Low ties are strong (ish). There are other things you can do to stiffen it up. The hip area is actually a lot less dependent on the ties.

 

[ToddMcF2002]

Using the Direct Lift calculator with myself as the required height underneath and my 65 Mustang up top it calls for 11.5 feet. A BelAir would require 12 feet and I've owned a few of those. So I'm shooting for 13 or 14 basically as high as it will go but could compromise at 12.5 feet I suppose.

 

[ToddMcF2002]

How much height do you want? Low ties are strong (ish). There are other things you can do to stiffen it up. The hip area is actually a lot less dependent on the ties.

Also I'd be interested to hear more about those things.

 

[firebirdparts]

Also I'd be interested to hear more about those things.

A hip roof is usually built as a ridge beam and rafters construction which is self supporting without the ceiling. The two hip rafters have enormous weight on them. Sometimes you'll see one with a supporting truss, flat on top, hidden underneath that kinda holds up some weight in the middle of the rafter spans. You may or may not have that.

It would be possible to build a truss or otherwise triangulate under each hip rafter, but I've never seen one done that way. I just assumed there is nothing clever in there blocking your way. If you decide you can do it on that side, then you just need to look in the attic and see what they did.

If for logistic reasons you just want to use the other garage bay, I think you'll be fine to do it there. You do need an engineer to look at it. You will weaken the structure when you raise the ceiling, but I think it's likely they will say it's okay.

 

[ToddMcF2002]

Thanks for that. I do have some pics. Luckily there is nothing but joists and its all wide open. There are a few supporting beams up there but nothing atypical. Peak is about 8' from the ceiling joists. Garage is 24x24

here is the hip roof side that I'm not touching
View media item 96248
The hip roof portion switches joist direction for the slope but again, not planning to touch this
Luckily there is nothing but joists and its all wide open. There are a few supporting beams up there but nothing atypical. Peak is about 8' from the ceiling joists. Garage is 24x24


The hip roof portion switches joist direction for the slope but again, not planning to touch this
View media item 96249
This is the bay attached to the house I'm planning to alter
View media item 96247
Its all 2x8 construction for the joists
View media item 96251

 

[theoldwizard1]

The hip roof portion switches joist direction for the slope but again, not planning to touch this
View media item 96249

Remember, the primary job of ceiling joists is to prevent the side walls from pushing out.

It is best to leave that one long joist in place that connects to the short joist running perpendicular to it. You might have to double it.

In theory (not a structural engineer), the joist can be replaced be rafter ties or collar ties.



The feasibility of this depends on

• Weight of the roof including snow load
• Dimensions of the rafters
• Spacing of the rafters
• Attachment of the rafter to the wall top plate
• Size of the rafter/collar tie

One GJ member went to the extreme and lag bolted a 3x3x1/4 piece of angle steel to the double top plate of the wall. That thing will not deflect now !

 

[Chris705]

Tagging onto what that old wizard says the ceiling joist will become a rafter tie (don’t confuse this with a collar tie) as it is raised up. The general rule of thumb is the rafter ties need to be located along the lower third of the rafter length. (Think this was mentioned previously) the rafters have been sized appropriately already. The ceiling joists were sized to span the depth of the garage, shortening them as they are raise up will work fine. Securing them to the rafters is the critical part. Using grk structural screws is a good thought as would a couple thru bolts. Often the rafters and ceiling joists are used in tandem to secure to the wall plates. When moving the joists up be sure to add some Simpson angle brackets to the rafters/wall junction with more screws.
Should have looked the way or wizards photo, spells out most of what I wrote....

 

[firebirdparts]

In your first picture, do you see the point where those 5 rafters and the ridge all come together in on spot? There is a ton of weight right there and you need to retain the joist that is under that, even if it influences the location of your lift a little bit.

If you take the joist out that is below that, it's not like the house will fall, but there is a lot of weight there and it would be nice to be strong there if at all possible.

 

[Grimpala]

In your first picture, do you see the point where those 5 rafters and the ridge all come together in on spot? There is a ton of weight right there and you need to retain the joist that is under that, even if it influences the location of your lift a little bit.

If you take the joist out that is below that, it's not like the house will fall, but there is a lot of weight there and it would be nice to be strong there if at all possible.

That's on the side he isn't messing with.