Meaning of "Exposed members"
Meaning of "Exposed members"
(OP)
What does "exposed" mean in the phrase "exposed members"? How would you convince the AHJ that's what it means?
In NFPA 13 2013, Table 8.6.2.2.1(a) has many interesting things going on...

A short snippet from the handbook giving us additional info:

If you look at the table where it says "Combustible unobstructed with no exposed members" under "Construction Type", I want to ask how this is possible to be constructed?
A couple of senior sprinkler nicet IV's have given me the interpretation that "exposed members" means "combustible members" such as wood. So having rigid metal frames or steel bar joists would not be counted as "exposed members", meaning this "Combustible unobstructed with no exposed members" type of construction is entirely practical and common.
However, if you interpret it literally, "exposed members" does not say "combustible members" and I would say it would literally apply to any member - including steel ones. But then the question is, is it even possible to construct a large-area roof without exposed members? If not, obviously there is more here than just the literal interpretation.
What does "exposed" mean in the phrase "exposed members"? How would you convince the AHJ that's what it means?
In NFPA 13 2013, Table 8.6.2.2.1(a) has many interesting things going on...

A short snippet from the handbook giving us additional info:

If you look at the table where it says "Combustible unobstructed with no exposed members" under "Construction Type", I want to ask how this is possible to be constructed?
A couple of senior sprinkler nicet IV's have given me the interpretation that "exposed members" means "combustible members" such as wood. So having rigid metal frames or steel bar joists would not be counted as "exposed members", meaning this "Combustible unobstructed with no exposed members" type of construction is entirely practical and common.
However, if you interpret it literally, "exposed members" does not say "combustible members" and I would say it would literally apply to any member - including steel ones. But then the question is, is it even possible to construct a large-area roof without exposed members? If not, obviously there is more here than just the literal interpretation.
What does "exposed" mean in the phrase "exposed members"? How would you convince the AHJ that's what it means?





RE: Meaning of "Exposed members"
Combustible = burns. (Wood for the most part but could be any other type building material like a plastic board.
How is "Combustible unobstructed with no exposed members" possible to be constructed?
How about support of mezzanine with glue-lam beams 7'-7" on center. Place a ceiling 7" below the bottom of the glue lams.
R/
Matt
RE: Meaning of "Exposed members"
If so, what's an example of a non-exposed (invisible) member?
RE: Meaning of "Exposed members"
RE: Meaning of "Exposed members"
Full Definition of EXPOSED
1
: open to view
2
: not shielded or protected; also : not insulated <an exposed electric wire>
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Matt
RE: Meaning of "Exposed members"
completely agree though that exposed shouldn't have anything to do with combustibility in-of-itself
still perplexing as to why it seems to be associated with combustibility from multiple people who have never met and some of whom are very experienced
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usually such behavior is a sign of something that was different in the past, talked about in a tech note, or something at least, because I agree it's a weird leap to go from a term like "exposed" to mean "combustible"
RE: Meaning of "Exposed members"
Chapter 3
Section 3.1, is the definition.
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Matt
RE: Meaning of "Exposed members"
Link
Link
about the definition of exposed, in the context in which it is used, seems like fire treated wood could be considered shielded or protected (from fire), steel could be considered shielded or protected (from fire), but non treated wood could be considered exposed (not protected from fire)
yet a see-through plastic ceiling down below some structural members means the beams are open to view, but obviously isn't what is intended
in short I don't think a merriam-webster dictionary definition is enough to get an answer, especially when the definition includes talk about "shielding/protection" and "shielding/protection" can change something from being "combustible" to "limited-combustible" or even "noncombustible".
RE: Meaning of "Exposed members"
RE: Meaning of "Exposed members"
The definition is correct. There is no way talk about "shielding/protection" can change the combustibility of an item. It changes if the heat can reach it, but not how it burns.
Is you pipe concealed or exposed in an office bldg. with ceilings?
If we use your interpretation and consider the glue-lams above the ceiling in my example as exposed, wouldn't the maximum listed spacing for a residential sprinkler attached to CPVC be 15'-0"? This is because to be installed "exposed", CPVC piping has specific criteria. One of which is no more than 15'-0" on center for sprinklers.
Why do you think we have an entire chapter, 8.15.1 addressing concealed installations?
Even in the link that works above, the terms are very distinct and different. Exposed/Concealed, Combustible/Non-Combustible.
You are trying to get wine from mixing apples and oranges...
R/
Matt
RE: Meaning of "Exposed members"
Mike McCann, PE, SE (WA)