• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

Hanging drywall from rafter ties?

Clonedad

Clonedad

Registered User
Joined
Feb 26, 2022
Messages
4
Location
Ga
Hey everyone! Looking to finish the upstairs of a 20x28 2 story garage, with the potential of this floor being an apartment one day if need be, so it would need to meet residential code.

Looking to do the ceiling with drywall/insulation. 2x8 Rafters are 16 on center. 2x4 rafter ties that span 20 feet. Roof is a 4/12. Rafter ties are hung 11” up from the top of the walls, with the top of the ridge being about 3’8” from the top of the walls.

Here are some photos:

https://imgur.com/hMvY0LA

https://imgur.com/fw0T5cl


Can I hang half inch drywall from these rafter ties w/ insulation? Or would the weight somehow compromise the function of the rafter ties?
 
The 2x4s might be too high to function as a rafter tie. The span of the 2x4s is too great to support drywall.
 
ICE said:
The 2x4s might be too high to function as a rafter tie. The span of the 2x4s is too great to support drywall.
Click to expand...
It’s in the bottom third, so I believe it should be fine correct?
 
With the suspended strong back at center, the 2x4 span seems to be about 6', assuming the connection is correct. Is 6' too great of span for 2x4 to support gwb and insulation? Too early on a Sunday to open the book.
 
Last edited:
R802.5.1 Ceiling Joist Size

Ceiling joists shall be sized based on the joist spans in Tables R802.5.1(1) and R802.5.1(2). For other grades and species and for other loading conditions, refer to the AWC STJR.

#2 southern pine at 16 inch centers spanning 20 feet is way over prescriptive code .
 
Chapter 8 Roof-Ceiling Construction

User note:

About this chapter: Chapter 8 addresses the design and construction of roof-ceiling systems. This chapter contains two roof-ceiling framing systems: wood framing and cold-formed steel framing. Allowable span tables are provided to simplify the selection of rafter and ceiling joist size for wood roof framing and cold-formed steel framing. Chapter 8 also provides requirements for the application of ceiling finishes, the proper ventilation of concealed spaces in roofs (for example, enclosed attics and rafter spaces), unvented attic assemblies and attic access.
 
patrickjames said:
R802.5.1 Ceiling Joist Size

Ceiling joists shall be sized based on the joist spans in Tables R802.5.1(1) and R802.5.1(2). For other grades and species and for other loading conditions, refer to the AWC STJR.

#2 southern pine at 16 inch centers spanning 20 feet is way over prescriptive code .
Click to expand...
The rafter ties don’t spam 20 feet, as they aren’t sitting on top of the walls. They probably span more like 15? And there is a suspended strong back above them in the center, which would probably eliminate sag?
 
Clonedad said:
They probably span more like 15?
Click to expand...
Counting stud spaces (9) seemed closer to 12', then half that because of beam. Pretty sure a 2x4 will do that.

The only question I have were the rafter spans derated because of raised ties? I see too often the assumption ties can be raised a third, with no mention of rafter span.
 
The rat run that is refereed to as a beam is there to provide support to the ties to prevent sagging. I would not ascribe any value of support for drywall to the rat run. I would also look at the rat run and the attachment to the ridge as a default ridge support. A ridge support should not land on ceiling joists that are remote to a bearing structure.

When the wind blows hard enough, the roof deflects and in turn the ceiling joist will deflect. That causes drywall to crack and fail at the fasteners. But hey now, I'm no engineer so there's no need to pay any attention to what I have to say. Do as you please and the outcome, whether good or bad, will hardly matter.
 
Last edited:
ICE said:
The rat run that is refereed to as a beam is there to provide support to the ties to prevent sagging. I would not ascribe any value of support for drywall to the rat run. I would also look at the rat run and the attachment to the ridge as a default ridge support. A ridge support should not land on ceiling joists that are remote to a bearing structure.
Click to expand...
I agree with this.
 
If you support a ceiling joist or rafter tie in the center of 12' joist/tie, what's the span? I think by ordinary definition of span, 6'.

Now, whether the joist to strong back connection or the vertical 2x4s supporting it are code compliant (certainly not prescriptively) is a different question.

There certainly are a lot of buildings with ceiling joists/rafter ties well under the code for their length that are supported with a vertical 2x4 and no rash of reported failures.

So get an RDP to look at it and do a quick sketch and seal it.
 
I'd attach to rafters not ridge board - which in this case looks as thick as 2by rafters - and probably use screws. The rafters are probably fine for load of gwb attached to them directly, so same load. As usual, more about the connections and what is permitted prescriptively versus requiring an RDP.
 
steveray said:
Hanging a rafter tie off of a ridge board is not a bearing point....But it might work.....
Click to expand...
Oh I'm sure that it works for supporting the rafter tie. I have asked for support of rafter ties many times. I have encountered garages with a drywall ceiling that is supported by rafter ties 4' apart.
 
So the rater ties bearing supports are the nails used to apply the rater tie into the side of the rafter. And the rafters having true bearing at the ends on the top plates.

Will it still remain a clear span or will there be a center wall added?
 
You must log in or register to reply here.
Top