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flat ceiling 2x4

darcar

darcar

Silver Member
Joined
Nov 12, 2009
Messages
129
Can someone direct me to a code section or other guidline that addresses framing members lying flat for a drop soffit framing?

Framer has used 2x4's flat spanning around 5 foot...
 
Actually you could just give it a nudge with your chin and if the soffit survives you've got a winner.
 
darcar said:
Can someone direct me to a code section or other guidline that addresses framing members lying flat for a drop soffit framing? Framer has used 2x4's flat spanning around 5 foot...
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What problem are you seeing with it?
 
The problem (I believe) is that the IRC does not address lumber used in this manner, if the applicant would like to provide verification via an alternative means (span table that addresses it) I am all for it...I know it probably works, but that is not my job....
 
steveray said:
The problem (I believe) is that the IRC does not address lumber used in this manner, if the applicant would like to provide verification via an alternative means (span table that addresses it) I am all for it...I know it probably works, but that is not my job....
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The code is silent on the matter of soffit framing. Perhaps this is a good example to follow?

Particularly since you know it ain't broke.

To put it another way, this a case where you don't believe there is a problem.

What is gained if you create one?
 
I've seen this done in raised ranch homes when the duct is in the garage and 2x4's are framed below the duct for gypsum. We called it a cage frame or fur-downs.

I've seen the span further than 5ft as well.

If the 2x4's span further than 6ft would you need hangers?

pc1
 
Oddly, I agree with brudgers on this one. The span tables are for stuctural loading, the soffit is a cosmetic application.
 
I have allowed 2 x 4's installed flat to span a max. of 4ft. Nothing to base it on other than I know of no problem associated with this installation method.
 
Would anybody ever be up there crawling around? If so, I would be worried about how it is connected to the adjacent framing. A gun nail in withdrawl is only good for about 40 pounds. If we size the joist for a 6 psf dead load (insulation 3 lb, sheetrock 2 lb, wood 1 lb) and 10 psf live load, a flat 2 x 4 (HF) spanning 5' is adequare by 5.5%.
 
steveray said:
Dead load is not structural?
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It's supporting it's own weight and a little bit of gypsum board. It's structural to the same degree that door butts and base cabinets are.
 
JBI said:
Oddly, I agree with brudgers on this one. The span tables are for stuctural loading, the soffit is a cosmetic application.
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Soffit-1.jpg


I too agree
 
I ran the beam as SPF studs, 5' span, 20plf loading.

Deflection = 0.234"

That's better than l/240.

20plf is really really conservative for this application.
 
The NDS and WFCM and the antiquated (used by trained people) wood design manuals had all of these and were "REFERENCED STANDARDS" in the codes for ages.

used by craftsmen who had framing squares and tape measures and knew things like - you need extra joists at tubs, and bearing and non-bearing walls. Trained and maybe even served an apprenticeship

hen along comes the larger volume more expensive "ICC Codes for Dummies Series" where if it ain't in a chart it obviously can't be allowed crowd......................sorry I'm Ranting. Time for my pill.
 
No the rant was based on code

the CFD's Chart Laden DIY manual is for "STRUCTURAL LUMBER"

the photo and resultant construction in not "Structural" - no load path to follow

R301.1 Application. Buildings and structures, and all parts

thereof, shall be constructed to safely support all loads, including

dead loads, live loads, roof loads, flood loads, snow loads,

wind loads and seismic loads as prescribed by this code. The

construction of buildings and structures in accordance with the

provisions of this code shall result in a system that provides a

complete load path that meets all requirements for the transfer of

all loads from their point of origin through the load-resisting elements

to the foundation. Buildings and structures constructed as

prescribed by this code are deemed to comply with the requirements

of this section.
 
If you want to question anything about the install, it would be reasonable to ask about the additional dead load on the main floor joists.

The code desn't specifically address the bedding requirements for ceramic floor tile, does that mean it can't be used?

Ben has provided the calculations that would be appropriate to make a determination, and clearly there is no issue viewing these as 'ceiling joists' based on span and load - and his factor of safety was very high in this instance. Had they put the 2x4s on edge, there is still no mechanism in the Code to rate them for span. The span tables start at 2x6. And again, the span tables are for joists and rafters not soffits.

If the project looks like mark handler's photo, I'd say much ado about nothing.
 
darcar said:
framing members lying flat for a drop soffit framing?
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I don't quite understand what you are describing. The key word soffit leads me to believe that this is the exterior of the building. And you have rafter tails that the framer is nailing to and then the 2X's go back into the exterior portion of the wall. Am I on the right track?
 
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