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Wood Truss Protection

Wood Truss Protection

Wood Truss Protection


I have a project that is a 2 story wood frame aprox. 5,000sqf per floor educational facility. Between 1st and 2nd floor and 2nd and roof they are using 18" wood trusses. The truss will have sheet rock attached directly to the bottom and a drop ceiling will be placed roughly 1'-6" - 2'-0" below. I'm following NFPA 13 2010. Section Bottom line is a truss is not a solid member. I am providing interstitial sprinkler protection for these areas. The problem i'm having is that the architect doesn't think the area is exposed cause the sheet rock is attached to the bottom. Well I think he's right if you look from the floor up but it you look inside the space the trusses are exposed.

Has anyone else had this problem? How was it explained?

RE: Wood Truss Protection

1st rule in NFPA 13 is your protect ALL areas. Then, you can look for areas to omit protection from. You have a concealed combustible space. Based on what you describe, sprinkler protection is needed. If they want to fill with non-combustible insulation then you can eliminate protection. However, be sure to use the specially listed sprinklers for your situation. It sounds like you have between 6" and 36" of clear space in a "flat" concealed space. This requires specially listed sprinklers. Tyco, Reliable, Viking, Globe and Victaulic all make a sprinkler that is listed for this specific application. Also be sure to fully read the data sheet. You have to do draft curtains every 1000 sq ft, or have full height walls that make 1000 sq ft compartments.

You may want to kindly suggest that the architect not try to step into fire sprinkler system nuances and you won't get into how the building should be designed smile

Travis Mack
MFP Design, LLC
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

RE: Wood Truss Protection

Mark, you are correct.

Went with a VK900 and the area is scheduled to have drafting every 1,000sqf. The kind suggestion is the problem I'm having. Other than manufactures spending tons of money to make a head specifically for this situation, I'm not sure hows else to brake it down.

RE: Wood Truss Protection

Break it down this way: Additional testing revealed that a standard spray sprinkler could not fully develop the sprinkler pattern in the shallow, flat concealed spaces. In order to address this, the manufacturers came up with the concealed combustible sprinkler. Part of the ability to pass the required tests were to compartmentalize to 1000 sq ft.

If he can't take that, then just say because that is what the standard states and if you are going to force this to be standard sprinklers then get your lawyer to draft me a waiver of liability for you deviating from the published standards based on the architects vast fire protection engineering experience. SMH!!!

Travis Mack
MFP Design, LLC
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

RE: Wood Truss Protection

Fill with non combustible insulation??

RE: Wood Truss Protection

Adding to Travis's comments,

The 1,000 square foot area limit is necessary because if a fire develops in the concealed space, containment of the heat is essential for the sprinklers to operate fast enough to control the fire.

Your architect is more than likely going to challenge the draft curtains because they are not required by IBC Chapter 7 if a building is protected using a NFPA 13 sprinkler system. However, the draft curtains are required as a condition of the sprinkler listing and for the design to be approved, they must be provided. If you go with this design approach be sure to demarcate the area of each draft curtain area - your fire AHJ will thank you.

The space can be filled with noncombustible insulation. If this option is selected, review the data sheet for the selected insulating material and confirm that it has successfully passed an ASTM E 136 test. If it hasn't been tested to this standard, it's not a compliant material in NFPA 13 or the International Building Code.

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