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Wood in Type IIB building

H

HDman

Member
Joined
Feb 18, 2016
Messages
3
Location
Colorado
We have detailed a ceiling with wood to create a light cove.

Our argument to do this was first based on the fact that this is blocking. The building department and us could not come to the same conclusion of the definition of blocking and they felt this was not blocking.

Therefore we proposed the following code section and argument:

  • Section 603 – Combustible Material in Type I & Type II Construction:
  • Exception 18; Nailing or furring strips as permitted by Section 803.11/803.11.1
    This exception allows combustible nailing and furring for interior finishes. Within these sections it states; the interior finish material shall be applied directly against such construction or to furring strips not exceeding 1 3/4 inches. This would be a compatible code section where there is a finish shown attached to a nailer which is of compliant thickness.
They are not buying into this argument either. Has anyone else come across a similar situation in a Type IIB building?

Thanks.
 
I don't know what your detail looks like but wood finishes are allowed in a Type ll building. Is their objection the framing of it? You can use non-com plywood to frame.
 
I am not "authorized" to attached an image. The wood part is creating the cove and then wrapped with drywall. Unfortunately it is already installed also.
 
Hdman

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There is no defined limit to the amount of blocking in the IBC in I and II construction....and FRTW is NOT noncombustible, but it might make some AHJ's more comfortable....Without a pic or drawing, it is hard for us to make the call, but it is the relevant AHJ you need to convince or find a way to appeal in the area you are in...
 
http://www.rci-online.org/interface/2001-03-hodgin.pdf

Word of caution about permitted use in Roof construction, I have seen this:

Chemicals in the FRT can react with the natural fibers of the wood, resulting in an overall brittle condition that occurs over time. This condition is seen as the primary cause of the splits and breaks in the wood roof framing.

...Chemicals used in the FRT have resulted in significant compromise to structural members. The loss of strength can cause premature failure of trusses. The modes of failure include heavy checking parallel and perpendicular to the grain, splitting, and full crossgrain breaks
 
I am not "authorized" to attached an image. The wood part is creating the cove and then wrapped with drywall. Unfortunately it is already installed also.
Click to expand...
Sounds like to me it's framing. If you put it up w/o using fire-retardant wood you might be SOL. I had a recent project were the contractor did not use FR plywood on a soffit and the AHJ let them post treat it. I thought that was a stretch and quite accommodating by the AHJ though.
 
This project is in Colorado and we are on the 2009 IBC.

Going to FRT is an option we are looking at, but we are also trying to avoid the rework. I was looking to see if any other people had similar arguments.

The drawing is noted as "blocking" but the building department does not agree with us on the definition of "blocking". Strange since we can put all kinds of blocking in walls and ceilings with no limit for finish and casework attachment.

Unfortunately the code does not define blocking so the they are using Webster's definition which doesn't help much: "a solid piece of material (such as rock or wood) that has flat sides and is usually square or rectangular in shape".

Ironically Webster's has another definition for blocking also: "the piece of wood on which the neck of a person condemned to be beheaded is laid for execution". I am starting to see the writing on the wall.
 
Not allowed - also it would or might be considered an interior finish if it is wood molding.

SECTION 805 COMBUSTIBLE MATERIALS IN TYPES I AND II CONSTRUCTION

805.1 Application.

Combustible materials installed on or embedded in floors of buildings of Type I or II construction shall comply with Sections 805.1.1 through 805.1.3.

Exception: Stages and platforms constructed in accordance with Sections 410.3 and 410.4, respectively.

805.1.1 Subfloor construction.

Floor sleepers, bucks and nailing blocks shall not be constructed of combustible materials, unless the space between the fire-resistance-rated floor assembly and the flooring is either solidly filled with noncombustible materials or fireblocked in accordance with Section 718, and provided that such open spaces shall not extend under or through permanent partitions or walls. 805.1.2 Wood finish flooring.

Wood finish flooring is permitted to be attached directly to the embedded or fireblocked wood sleepers and shall be permitted where cemented directly to the top surface of fire-resistance-rated floor assemblies or directly to a wood subfloor attached to sleepers as provided for in Section 805.1.1. 805.1.3 Insulating boards.

Combustible insulating boards not more than 1/2 inch (12.7 mm) thick and covered with finish flooring are permitted where attached directly to a noncombustible floor assembly or to wood subflooring attached to sleepers as provided for in Section 805.1.1.

(Essentially the blockers/sleepers are covered by a finished product and not directly exposed) and

[F] 806.5 Interior trim.

Material, other than foam plastic used as interior trim, shall have a minimum Class C flame spread and smoke-developed index when tested in accordance with ASTM E 84 or UL 723, as described in Section 803.1.1. Combustible trim, excluding handrails and guardrails, shall not exceed 10 percent of the specific wall or ceiling area in which it is attached.

If the material installed does not have an listing in accordance with ASTM E84 or UL 723 and exceeds 10% of the ceiling area..... take it out.
 
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