Fire stops required around type B-vent

**Terry Beck** · 07-01-2008, 07:25 AM

Maybe I am getting messed up by terminology. I have always assumed that exhaust vents for gas fuel appliances (furances, water heates, etc - in this case a Burnham gas hot water boiler) require a fire stop when they pass through a ceiling (i.e. of a utility room) into the attic space. Though, I am not sure which specific code (IRC) applies.
Back in March, there was a thread in which Jerry Peck said, "The collar *is not* a proper firestop or draftstop - its only purpose is 'purtyness'.

IRC R602.8 says "Fireblocking required .... to form an effective fire barrier between stories... etc" (... around all vents, etc).

There is referance to fireblocking required for chimneys and fireplaces (R1003.19), but does this not apply to gas appliance vents?

M1801.9 refers you back to R602.8.

See picture. There is no collar, or support, or insulation shield, and the clearance is less than the 1" required for type-B exhaust vent. But Jerry's comment confused me. Doesn't is also need a fire stop (Collar) around the exhaust vent where it passes through the ceiling??? Which code reference is the proper one?

Similar Threads:

**Terry Beck** · 07-01-2008, 07:31 AM

sorry, a picture is worth a 1,000 words,
here's are pictures

**Jerry Peck** · 07-01-2008, 09:52 AM

Originally Posted by Terry Beck

Back in March, there was a thread in which Jerry Peck said, "The collar *is not* a proper firestop or draftstop - its only purpose is 'purtyness'.

Terry,

What I was referring to is when some installers use the collar as a "firestop or draftstop", and a collar is not intended nor approved for that purpose.

To answer your question in the post above, you would need to go to the manufacturer's installation instructions.

(underlining is mine)
Metal-Fab: http://www.mtlfab.com/media/L041r.pdf Page 1 - see Installation: 3. When a combustible floor is penetrated by B-Vent, a MFS firestop or MSP support plate is used to close the opening. If the area above the ceiling is an attic, the firestop or support plate is mounted above the joist to assure that insulation does not drop into the joist area. / Page 2 - see Figure 1.

Snap Fast: http://www.continentalindustries.com...nt-Install.pdf Page 1 - see 10. Provide 26 ga. metal firestops (-GF) at each floor level. Locate firestop on flooring or subflooring to prevent saw dust and chips collecting against vent. Frame opening to attic on all four sides and place firestop on top of attic floor or joists to prevent insulation or other debris from contact with vent pipe. / Page 2 - see both figures.

American Metal Products (AmeriVent): http://www.ampcostacks.com/pdfs/bven...structions.pdf Page 2 - see 11. Firestops must be used where vents pass through floors or ceilings. / Page 4 see - B. Fire Supports

Simpson-Dura-Vent: http://www.duravent.com/docs/instruct/L204A_apr00.pdf Page 2 - see Fig 1 / Page 3 - see Fig 2 / Page 4 - see Steps for Typical Installation 3.

Ceiling Support

. For a ceiling supported system, install the Square Firestop/Support as shown in Figures 6, 7, and 8. The Firestop Support must be framed in and the dimensions are shown in Table 1 and shown in Figure 4. Firestop Supports are currently manufactured for pipe sizes of 3" through 12" only. Larger sizes may be locally fabricated from sheet metal, provided that the mandatory 1-inch clearance is maintained, the pipe is adequately supported, and the installation is acceptable to Local Authorities. In multistory buildings, a Firestop/Spacer must be provided at every floor /ceiling level other than the first floor which requires a support.

**Bob Harper** · 07-01-2008, 10:30 AM

In cases such as shown in the photos, I recommend you shoot pics of the listing sticker on the B-vent. Once back at the office, you can reference chapter and verse where that mfr. requires a listed firestop, part#123xyz and so on. BTW, I doubt you have the requisite 6" clearance from that single walled pipe to the wall and ceiling. The single walled is not properly supported either. In the attic, you would need a listed firestop (and fire blocking per IRC 602.8) AND an attic insulation shield to keep the insulation and Romex off the vent or better yet, Vertical Fireblocking, which is needed because I see plywood. The presence of plywood means there is a reasonable expectation the occupants can access that area where they can be expected to come in contact with the vent. This could result in personal injury or damage to the vent. This can be addressed by simply enclosing the vent with 2x4s and plywood while maintaining clearances. You also woul want to double check the appliance listing for suitability of this vent and any special venting considerations.

As with all listed products and appliances, you answer always starts with the listed instructions.
HTH,
Bob

**Terry Beck** · 07-01-2008, 01:35 PM

Thanks Bob & Jerry. That confirms what I thought. Your help is deeply appreciated.

I see SO MANY exhaust vents in this region, even in newer homes, that don't have proper firestops, supports, clearances, etc, that after awhile I begin to doubt myself on occasion. I have installation guides from some of the manufacturers, but am not always clear which IRC or Mechanincal code is pertinant in case I have to back myself up with the contractor.