When you look closely at it you'll see that TJI's are composite wood joist, not solid wood joist. Studies show they fail in 6 Min in a fire as compared to up to 27 Min for solid wood joist or traditional framing. Yes you have the 3000 Sf in both the crawl space and in the "Adjacent space" above the crawl space.
To avoid this you could "fill" with non-combustible insulation. 11-7/8" TJi=12" batt insulation. Why this exception. Because the insulation will both starve the fire of Oxygen, and slow the spread of fire in the joist space. Thom McMahon, SET Firetech, Inc. 2560 Copper Ridge Dr P.O. Box 882136 Steamboat Springs, CO 80488 Tel: 970-879-7952 Fax: 970-879-7926 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of A.P.Silva Sent: Thursday, May 07, 2009 8:09 PM To: [email protected] Subject: RE: Combustible crawlspace No takers for my original questions. So let me try again. 16" deep TJI's (composite wood construction). Sprinklers can be upto 6" below the bottom of the TJI's and comply with NFPA for obstructed construction. Same scenario, but with drywall or insulation at the bottom of the TJI's forming an unsprinklered combustible space. Does it trigger the 3000 sq.ft. design? If it does, I fail to see the logic. Tony -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of A.P.Silva Sent: May 5, 2009 2:41 PM To: [email protected] Subject: Combustible crawlspace A crawlspace comprising of a wood deck, 16" deep TJI's and open space below the TJI's. Between the TJI's there is batt insulation, kept in place with wire mesh attached to the bottom flanges of the TJI's. The insulation is only couple of inches (approx) thick and doesn't fill the entire TJI space. The crawlspace is 1 foot deep at the perimeter and 4 feet at the centre of the building. The depth is from bottom of the TJI's to the ground. The crawlspace is being sprinklered. Questions: (1) Are the pockets formed by the TJI's and insulation have to be sprinklered? If there was no insulation, the sprinklers could be below the bottom of the TJI's due to obstructed construction. The pockets are less than 160 cuft in volume, but there is no non-combustible or limited combustible ceiling at the bottom. Just non-combustible insulation and wire mesh. My opinion is the insulation can be ignored. The sprinklers will be at the permitted distance below the deck, so the pockets don't have to be sprinklered and the 3000 sq.ft. design is not required. Anyone disagree? (2) The height below the bottom of the TJI's vary from 1 foot to 4 feet. Are combustible concealed space sprinklers required? (using NFPA 13, 2007) I don't think it will be a good design to have them only at the perimeter and standard heads at the centre. Section 8.15.1.7 states that the listed sprinklers are "permitted" to be used to protect composite wood joist construction less than 36" "between the top of the bottom joists and bottom of the upper jpists". (In other words the depth of the TJI's. Could this be a mistake, as the TYCO cut sheets show this distance from the bottom of the TJI's to the ceiling). In anycase, it appears that the listed heads don't have to be used for composite wood joist construction, due to the use of the word "permitted". Anyone agree/disagree? Sub-questions: (3) If the construction was combustible wood truss or joists, the listed sprinklers may have to be used, depending on the height of the space. What happens when the height varies such as in my case? (4) NFPA imposes the requirement of cc sprinklers depending on the depth of the space. However, Tyco imposes other restrictions, such as maximum 54" from deck to deck for solid wood joist consruction. What happens if Tyco requirements are not met, and the listed heads are required by NFPA? Tony _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
