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Wood door frame backing studs in Type 2B building?

R

redcoat

REGISTERED
Joined
Dec 23, 2024
Messages
18
Location
Raleigh NC
Hi,

Newbie here. We are expanding our venue and the framer has just completed adding new interior walls (non-load bearing) with metal studs to deck. He told me he needed to add wood trimmer studs around the doorways to make it possible / easier to install door frames and casing nailing into wood instead of metal studs. He added double studs on top and both sides.

The inspector flagged this, though, and said the only way to do that is to use flame retardant 2x4's.

Can someone please help me under the best path forward please? Do I need to get him to replace current wood trimmer studs with metal? I can't find anywhere local that sells fire retardent 2x4's?

I will be very grateful for the advice!

cheers, David
 
The inspector is wrong. North Carolina Building Code, section 603.1

603.1 Allowable Materials​


Combustible materials shall be permitted in buildings of Type I or II construction in the following applications and in accordance with Sections 603.1.1 through 603.1.3:
  1. Fire-retardant-treated wood shall be permitted in:
    1. Nonbearing partitions where the required fire-resistance-rating is 2 hours or less.
    2. Nonbearing exterior walls where fire-resistance-rated construction is not required.
    3. Roof construction, including girders, trusses, framing and decking.
      Exception:In buildings of Type IA construction exceeding two stories above grade plane, fire-retardant-treated wood is not permitted in roof construction where the vertical distance from the upper floor to the roof is less than 20 feet (6096 mm).
  2. Thermal and acoustical insulation, other than foam plastics, having a flame spread index of not more than 25.
Exceptions:
  1. ...
  2. ...
  3. ...
  4. ...
  5. ...
  6. Millwork such as doors, door frames, window sashes and frames.
  7. ...
  8. ...
  9. ...
  10. ...
  11. ...
  12. ...
  13. ....
  14. Blocking such as for handrails, millwork, cabinets and window and door frames.
  15. ...
  16. ...
  17. ...
  18. Nailing or furring strips as permitted by Section 803.13.
  19. ...
  20. ...
  21. ....
  22. ...
  23. ....
  24. ....
  25. ....
  26. ....
  27. ....
Click to expand...

The 2021 IBC Commentary adds this:

Untreated wood: Numerous items in the list of Section
603.1 permit the use of untreated wood in Types I
and II construction. Blocking or nailers used to support
fixtures, railings, cabinets or interior and exterior finishes
are permitted within walls and partitions required
to be of noncombustible construction in accordance
with Item 14. Item 18 permits combustible nailers and
blocking as stipulated in accordance with Section
803.15. Section 803.15.1 indicates that “furring strips
not exceeding 13/4 inches (44 mm)” are permitted to be
used in noncombustible construction for securing trim
and finishes. Item 27 also permits specific nailers used
with parapet construction to be of combustible material.
Although locating these combustible elements
within noncombustible frame partitions is not specifically
identified in this section, the presence of combustible
nailers within noncombustible construction types,
other than concrete and masonry, represents an
equivalent circumstance. Therefore, it is the code is
intended to permit the use of combustible nailers and
blocking within Types I and II construction.
Click to expand...
 
Yankee Chronicler said:
The inspector is wrong. North Carolina Building Code, section 603.1



The 2021 IBC Commentary adds this:
Click to expand...
Hello!

Thanks so much for the response.

I wonder if the issue is the framer used 2 2x4's instead of 1, and exceeded the 13/4 inches?

Picture here: https://thehays.com/misc/door blocking.jpeg

We are under a tight timeline - would you recommend with remove a 2x4 and adjust metal studs?



door blocking.jpeg
 
Last edited by a moderator:
redcoat said:
Hello!

Thanks so much for the response.

I wonder if the issue is the framer used 2 2x4's instead of 1, and exceeded the 13/4 inches?

Picture here: https://thehays.com/misc/door blocking.jpeg

We are under a tight timeline - would you recommend with remove a 2x4 and adjust metal studs?
Click to expand...
It has nothing to do with the 1-3/4" furring strip and more than likely because they doubled up the studs. Our experience is that knowledgeable contractors use FT wood for blocking, even though they don't have to. I don't even like how they stacked the studs around the doorway. I would not have framed it like that, but I am talking from a non-code standpoint.
 
And hopefully they follow code when they are fastening FRTW....

2304.10.6.3​

Fasteners, including nuts and washers, for fire-retardant-treated wood used in exterior applications or wet or damp locations shall be of hot-dipped zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Staples shall be of stainless steel. Fasteners other than nails, staples, timber rivets, wood screws and lag screws shall be permitted to be of mechanically deposited zinc-coated steel with coating weights in accordance with ASTM B695, Class 55 minimum.

2304.10.6.4​

Fasteners, including nuts and washers, for fire-retardant-treated wood used in interior locations shall be in accordance with the manufacturer’s recommendations. In the absence of manufacturer’s recommendations, Section 2304.10.6.3 shall apply.
 
jar546 said:
It has nothing to do with the 1-3/4" furring strip and more than likely because they doubled up the studs. Our experience is that knowledgeable contractors use FT wood for blocking, even though they don't have to. I don't even like how they stacked the studs around the doorway. I would not have framed it like that, but I am talking from a non-code standpoint.
Click to expand...
Hi, how would you recommend framing them? Just a single 2x4 next to metal stud?
 
The code does not specify a maximum thickness for your door bucks in the exception that allows them to be installed in Type II construction. I contend that your inspector does not have a valid code section to write that correction with. Given that the same list of exceptions would allow you to legally cover every wall surface with floor-to-ceiling cabinets (leaving out the requirements in the "finishes" chapter), I don't think a few extra 2x4s are a deal breaker.

In his defense, there are a lot of exceptions in that section to keep track of. If you point it out, he may just say "Oh, my bad" and remove the correction. That is what I would do in his place. However, this approach must be used cautiously because many inspectors do not have that basic level of ethics or integrity.
 
BN4537 said:
The code does not specify a maximum thickness for your door bucks in the exception that allows them to be installed in Type II construction. I contend that your inspector does not have a valid code section to write that correction with. Given that the same list of exceptions would allow you to legally cover every wall surface with floor-to-ceiling cabinets (leaving out the requirements in the "finishes" chapter), I don't think a few extra 2x4s are a deal breaker.

In his defense, there are a lot of exceptions in that section to keep track of. If you point it out, he may just say "Oh, my bad" and remove the correction. That is what I would do in his place. However, this approach must be used cautiously because many inspectors do not have that basic level of ethics or integrity.
Click to expand...
Thanks. I ended up finding fire retardant 2x4s so we just switched them out. Happy to say he passed everything today
 
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