"Combustible" concealed space? 1

[SprinklerDesigner2]

I have a two story bank building.

The first two floors are non-combustible construction with metal studs, masonry and drywall.

The attic is wood truss and will need to have a dry system protecting the space.

The architectural drawings shows batt insulation between the bottom chords of the truss. It appears the bottom of the wood trusses will be exposed.

Here's a screen capture.

http://img211.imageshack.us/img211/3182/concealedspacell8.jpg

My question is will the space between the bottom of the wood truss and second floor suspended ceiling need sprinklers?

From NFPA #13 - 2002

8.14.1.2.13 Concealed spaces below insulation that is laid directly on top of or within the ceiling joists in an otherwise sprinklered attic shall not require sprinkler protection.

I think this applies, the space doesn't need sprinklers but I would feel better with confirmation.

Thanks

 

[cdafd]

I would say yes

if it looks like wood it burns like wood.

can they sheet rock it to cover it?? verses the sprinklers??

 

[TravisMack]

I think the section you quoted from NFPA 13 directly addresses your situation and sprinklers would not be req'd in that interstitial space you have there.

You have sprinklers at the ceiling and in the space above the insulation.

So, 1 for and 1 against...let's see how it tallies up..

Travis Mack
MFP Design, LLC

 

[stookeyfpe]

Nope, sprinklers are not required as indicated in Travis's post.

 

[cdafd]

With all due respect to the great HAZ and others

believe the section quoted does not address what the picture shows.

WHAT IF, oh no, the fire starts above the drop ceiling and below the exposed bottomof the wood truss,

1. the attic sprinklers are ot going to do any good till the roof burns off.

2. the sprinlers below the drop ceiling are not going to do any good till the building burns down

to me if you pop a ceiling tile and see wood and there is no 8.14.1.2 section that does not require sprinklers you sprinkle it.

 

[cdafd]

appears you have a three foot VOID space??????? combustible type.

 

[SprinklerDesigner2]

cdafd,

Yes, drawings show anywhere from 2' to 4' void space but there are two considerations which lead me to think sprinklers were not required.

There section 8.14.1.2.13 I quoted. Accoding to this even if the construction below the insulation was combustible, say wood studs were used instead of metal studs, sprinklers still wouldn't be required.

Consider as well non-combustible or "limited combustible" spaces.

8.14.1.2* Concealed Spaces Not Requiring Sprinkler Protection.
8.14.1.2.1 Noncombustible and limited combustible concealed spaces with no combustible loading having no access shall not require sprinkler protection. The space shall be considered a concealed space even with small openings such as those used as return air for a plenum.

I don't feel I am qualified to determine what is "limited combustible" so I don't. That being said I do know just because you see wood doesn't necessarily mean it has to be sprinklered. When I have a project where there limited is a question I have it reviewed by a FPE because that's their job.

 

[Oremus]

I voted for it before I voted against it. I've interpreted that code to mean no sprinklers were neccessary but this was clarified in the 07' code and sprinklers are indeed neccessary in this particular case:

nfpa #13 2007: 8.15.1.2.13 Concealed spaces below insulation that is laid directly on top of or within wood joists or composite wood joists used as ceiling joists in an otherwise sprinklered concealed space, with the ceiling attached directly to the bottom of the joists, shall not require sprinkler protection.

I think the earlier intention prior to 2007 was that batt insulation laid on top of the bottom chord of truss (or joist) sometime had pockets due to the insulation actually being tented over piping, light fixtures etc... and was referring to no added protection in this case.

 

[cdafd]

nfpa 3.3.14

3.3.14 Limited-Combustible Material. A building construction material that does not comply with the definition of noncombustible material that, in the form in which it is used, has a potential heat value not exceeding 3500 Btu per lb (8141 kJ/kg) (see NFPA 359, Standard Test Method for Potential Heat of Building Materials), and that complies with either of the following, (a) or (b). Materials subject to increase in combustibility or flame spread rating beyond the limits herein established through the effects of age, moisture, or other atmospheric condition shall be considered combustible. (a) Materials having a structural base of noncombustible material, with a surfacing not exceeding a thickness of in. (3.2 mm) that has a flame spread rating not greater than 50. (b) Materials, in the form and thickness used, other than as described in (a), having neither a flame spread rating greater than 25 nor evidence of continued progressive combustion and of such composition that surfaces that would be exposed by cutting through the material on any plane would have neither a flame spread rating greater than 25 nor evidence of continued progressive combustion.







would say 8.14.1.2.13 would apply if there was some non com attached to the bottom of the wood truss.

if you read the section to me it is saying that the attic sprinklers would wet the wood/ insulation,

but do not see that happening if the fire starts in the void area above the drop ceiling.

once again if there was another section that applies would not require them.

also would look to see if there is an ignition source in the void space.

I know I have gotten my hand slapped for saying that before. slap away.

 

[Cidona]

NFPA 13, 2007 section 8.15.1.2.16, A.8.15.1.2.16 and figure A.8.15.1.2.16 seem to address this situation and allow sprinklers not to be ommitted. There is limitations of the specs of the insulation.

 

[Cidona]

I meant shall be permitted to be ommitted - as in no sprinklers required.

 

[SprinklerDesigner2]

"NFPA 13, 2007 section 8.15.1.2.16, A.8.15.1.2.16 and figure A.8.15.1.2.16 seem to address this situation and allow sprinklers not to be ommitted. There is limitations of the specs of the insulation.

I meant shall be permitted to be ommitted - as in no sprinklers required."

I don't have a copy of 2007 yet having put it off since we're still operating on the 2002 edition.

Can someone copy and paste NFPA 13, 2007 section 8.15.1.2.16, A.8.15.1.2.16 and figure A.8.15.1.2.16? Well, not the figure.

 

[Cidona]

8.15.1.2.16* Concealed spaces formed by noncombustible or limited combustible ceilings suspended from the bottom of wood joists that have insulation filling all of the gaps between the bottom of the trusses or joists, and where sprinklers are present in the space above the insulation within the trusses or joists, shall not require sprinklers protection. The heat content of the facing, substrate, and support of the insulation material not to exceed 1000 Btu/ft2 (11,356 kJ/m2)

A.8.15.1.3 See figure A.8.15.1.2.16

Picture is a bit blurry but should help.

 

[Cidona]

Just to clarify the picture:

The description under it says 'Figure A.8.15.1.2.16 One acceptable arrangement of a concealed space in a truss construction not requiring sprinklers.

To the left under the insulation it says 'Concealed space below truss bottom chords.'

 

[SprinklerDesigner2]

Cidona,

That appears to be exactly the situation I am dealing with.

I am going to order the handbook tomorrow.

Thanks.

 

[Cidona]

No problem.

 

[cdafd]

8.15.1.2.16* Concealed spaces formed by noncombustible or limited combustible ceilings suspended from the bottom of wood joists, composite wood joists, wood bar joists, or wood trusses that have insulation filling all of the gaps between the bottom of the trusses or joists, and where sprinklers are present in the space above the insulation within the trusses or joists, shall not require sprinkler protection. The heat content of the facing, substrate, and support of the insulation material shall not exceed 1000 Btu/ft2 (11,356 kJ/m2).


not sure if your set up meets ALL requirements of this section