# "Concealed spaces not requiring sprinkler protection" (NFPA 13 8.15.1.2.1)



## Code Neophyte (Dec 15, 2010)

We have an I-1 structure of V-B construction being constructed with an NFPA 13 system.  The roof structure is a 6/12 gable roof, constructed of light gauge steel trusses and 5/8 CDF plywood sheathing (shingled roof).  Because of the width of the building, the 6/12 pitch yields a rather large "attic" space above the ceiling.  The sprinkler drawings that have been submitted do not provide attic coverage, citing the section (NFPA 13 8.15.1.2.1), which exempts concealed spaces of non-combustible construction.

The question is:  Does the commodity fir plywood roof sheathing make this a combustible concealed space?


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## High Desert (Dec 15, 2010)

Look at the definitions in NFPA 13 for Noncombustible and Limited Combustibles. I don't think plywood will meet the ASTM test.


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## FM William Burns (Dec 15, 2010)

FRT is what may be used in applications considered under the provisions for non/com spaces in accordance with NFPA 13 if I'm not mistaken.


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## FM William Burns (Dec 15, 2010)

FRT is what may be used in some applications considered under the provisions for non/com spaces in accordance with NFPA 13 if I'm not mistaken.


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## cda (Dec 15, 2010)

what is the rest of the attic area or ceiling/ studs of the floor below made out of ??? wood???

my call is if you can see wood you sprinkle, now if they want to sheetrock so you do not see the roof deck, and there is no other wood in the attic area, then they are good to go.


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## Code Neophyte (Dec 16, 2010)

cda said:
			
		

> what is the rest of the attic area or ceiling/ studs of the floor below made out of ??? wood?


All the rest of the attic is non-combustible:  Light-gauge steel trusses, fiberglass insulation, gypsum ceiling, walls beneath are steel studs - everything but the roof sheathing, which is _not_ FRT.

So the consensus is that it does not meet the requirements for the exemption??

Thanks, by the way, for helping with this...


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## cda (Dec 16, 2010)

like fm reply either sprinkle or use wood that meets nfpa 13 for non com or limited

Yes I would tell them to sprinkle if I could see the wood


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## steveray (Dec 16, 2010)

Not to get off topic....but is there a fire treated wood that meets ASTM E 136? Which I believe is the test for noncombustibility? Every time I have seen it here...it has not...


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## mtlogcabin (Dec 16, 2010)

Do the steel trusses have the correct coatings for FRT to be used? If the hangers and connectors have to be properly coated then the same logic would apply to steel trusses that will come in contact with FRT. The preservatives are corrosive to steel over time


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## Code Neophyte (Dec 16, 2010)

Thanks, mtlogcabin - good points!  I'll try to file all of this information away in my unreliable memory for the next project that comes along.

In this particular case, the sprinkler plans were a deferred submittal; the building plans were approved, which included notes indicating a full '13' system.  Now the trusses are up, sheathed, shingled, and they are ready to hang ceilings.  I would doubt that complete removal of the roof structure is a viable option at this point.

Oh well!!


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## cda (Dec 16, 2010)

Sheetrock or treated wood to cover the wood deck would eliminate sprinklers

Just have to figure which is cheaper


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## steveray (Dec 16, 2010)

Good point about the treated and steel framing MT....they do usually spec stainless fasteners, but I have never heard anyone address the framing...


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## TJacobs (Dec 20, 2010)

What FM said...I believe the use of FRT is a permitted exception in NFPA 13...


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## code2driver (Jan 19, 2011)

cda, you mention if you can't see wood, you don't have to sprinkler.  Would you apply that criterion to layed-in ceiling tiles within 6 inches of the bottoms of the joists?


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## cda (Jan 19, 2011)

Have to look at 13 to see what it says

Seem to remember it says sheet rock or similar attached


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## Builder Bob (Jan 20, 2011)

Code2Driver ---- I would not allow it for the following reasons -

ACT tiles are not permanent

The fuel gas code states that this area (between the ACT tile and the wood joist/flooring syste) is not a concealed space -

ACt tiles do not count as a thermal barrier for building envelopes ( allows air movement)

To many times while performing fire inspections, ceiling tiles are missing due to moisture problems, IT Cables, phone cables, or removed for access and never put back.

JMHO - yours and others may vary greatly.


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