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Silicone Roof Jack with Class A Chimney

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by mchristo, Dec 8, 2009.

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  1. mchristo

    mchristo Member

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    I'm installing a class A chimney through a roof that has metal roof panels.

    I think the easiest install of the flashing around the chimney is with a Silicone Rubber Roof Jack. The bottom of the roof jack has a piece of aluminum that is soft enough to form a perfect fit around the contours of the roof panel to get a good seal.

    They have two types of rubber.

    1. is EDPM rubber that is rated to 212 degrees F.
    2. is Silicone rubber that is rated to 437 degrees F.

    I'm guessing the EDPM is definitely not rated high enough for the class A, but the Silicone would be ok at 437 degrees?

    would the EDPM work? there is a big difference in price!
    thx

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  2. Hogwildz

    Hogwildz Minister of Fire

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    Use the silicone
  3. begreen

    begreen Mooderator Staff Member

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    +1 - listen to the man. He knows his roofing stuff.
  4. summit

    summit Minister of Fire

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    is it a standing seam roof, or corrugated w/ the screws? if its standing seam, there is an easier (and prettier) way to do this than the flimsy silicone boot.
  5. Metal

    Metal Minister of Fire

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    Neither will work unless you keep them at least 2" (or whatever the clearance to combustibles for your pipe is) from the pipe. Silicone and EDPM are classified as combustible. There is a company that sells a kit with standoffs to ensure they don't touch, but it is very expensive. The best/cheapest way is to get a standard flashing, cut a hole to just fit around the cone portion, and then install it from the bottom and then silicone around the top of the cone to prevent leaks.
  6. Eric Gradoia

    Eric Gradoia New Member

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    Hey Summit:

    I'm curious to know the method your talking about. I'm going got have to go through a modern standing seam metal roof when I run another chimney and have been wondering how to deal with this. I was going to try and avoid the problem by going through the ridge, but if there is a way to deal with the seams that comes out water proof and decent looking I'd consider that, it would eliminate the need for me to use offsets.
  7. summit

    summit Minister of Fire

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    drill your pilot hole thru the roof. Then center the opening at the top of the cone up w/ your pilot hole. Using a marker (or even a fog of spraypaint) trace out the inside opening of the flashing onto the roof. cut that oval out of the metal roof w/ a grinder (with a cutting wheel) or snips. Next, measure 2/3 the way downhill on the oval and cut an even slit laterally the width of the flashing. Next, slide the flashing upwars thru the slit, putting a fine bead of silicone where the seams meet and a couple self tapping pole barn (rubber gasketed roofing screw) where the bottom and top corners of the flashing are to keep it from sliding out... This method looks nice, (even if you have to cut a seam level w/ the roof to accommodate the lower overlap) and requires minimal silicone... it also give lots of natural overlap to let water flow over like a shingle, not back up and around.
  8. Hogwildz

    Hogwildz Minister of Fire

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    The silicone boot is rated over 400 degrees. If his Class A gets that hot on the outside skin, that high up, he has more problems to worry about than the silicone boot.
    And what makes you think the silicone your telling him to caulk around the top of the cone is any better than the silicone boot?
    BTW, just cutting a hole and popping the cone up through & caulking is asking for a sure leak down the road. Guaranteed.

    Summit has a good suggestion.

    There is also not much room for much sealant, and the small corners on each side of the slot may be susceptible to leaks. If done correctly and sealed good, Summit's suggestion is a good one. As with any way its done, if not done carefully and correctly sealed, its going to leak. Good suggestion Summit.
  9. gasavage

    gasavage Member

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    This is a pic of what I did on my pole barn. I bent & cut a standard flashing. Excel makes a metal roof flashing like this & has insructions in their installation manual. I was fortunate to be near the ridge, so I didn't have to cut a slit for the flashing. (Note: I was in the middle of installation when I took the pic.)

    Attached Files:

  10. Eric Gradoia

    Eric Gradoia New Member

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    Summit:

    Many thanks for the information. Great idea.

    Gasavage: That's the same roof profile that I'll be dealing with. You're lucky you were so close to the ridge. I'm considering just going through the ridge (no ridge pole to deal with) and dealing with an offset down below.

    Thanks fellow burners,

    Best, CR
  11. mchristo

    mchristo Member

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    I have a very similar if not the exact same profile roof panel as the last picture posted by Gasavage.

    The silicone is rated to run continuous at 437 degrees and intermitent up to 500 degrees.

    I would think (As Hogwildz said), if the outside of that class A gets to 500 degrees, then I'd think the 2" clearance to combustible/wood will come into play much sooner than the silicone will melt or burn.
  12. Metal

    Metal Minister of Fire

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    You're wrong Hogwildz, the silicone around the cone will be more then the 2"(or whatever the Type 103HT pipe is listed for) clearance to combustibles that is required. UL defines "combustible," not me. You can do anything, but that doesn't mean you should.
  13. Hogwildz

    Hogwildz Minister of Fire

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    The top of the cone would be the part that contacts or is about 1/2" from the pipe. So YOUR wrong. Unless you mean around the top of metal roofing where the cone goes though and meets the flashing.
    Either way, as I said before, if you reach anywhere near the rated temp of the silicone, your going to have a much bigger problem than that silicone boot.
    One more note, what would you suggest everyone seal the storm collar with if silicone is not good? I guess 99% of all members here sealed their storm collars with the wrong stuff then?
    That pipe ain't reaching nowhere nears 400 on the outer shell, in normal use & output. If there is a chimney fire, then as stated before, the silicone is the least of the worries.
    I'm done with you, you may go now.

    mchristo, let us know how ya make out, and post some photos.
  14. JerseyWreckDiver

    JerseyWreckDiver New Member

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    Silicone tubing is what is spec'ed by boiler manufacturers and building codes to be used to drain condensate from vent pipes on class I & II boilers. The drain fitting is within several feet at most from the beginning of the exhaust flow... If it can handle that it can handle being outside in winter on the outside of a double walled pipe. It is approved by the building codes for that use.

    or you can just go here

    http://www.selkirkcorp.com/Heatfab/Product.aspx?id=7180

    and look at this;

    Saf-T Vent EZ Seal

    Saf-T Vent EZ Seal is the strongest special gas vent.Saf-T Vent EZ Seal is the fastest and most reliable venting solution for Category I, II, III, and IV gas appliances – with no RTV sealant required.

    Single Wall

    *
    AL29-4C® Stainless Steel
    *
    3” through 16” diameters
    *
    Factory built-in silicone seal
    *
    3”-5” primarily for Residential applications
    *
    Tested and Listed to UL1738/ULCS636 by Underwriters Laboratories, Inc



    Hog & Summit know what their talking about.
  15. mchristo

    mchristo Member

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    I think you guys are probably both correct. From a purely technical or code perspective, I don't think the Silicone roof jack would be approved.

    But...I think it will work just fine.

    The approved method for flashing it is with the metal cone and a metal storm collar sealed with RTV silicone (rating 600 degrees). If something went wrong there would not be enough silicone there to add enough combustible material to contribute to a fire.
    More importantly, (as has been said before) if the exterior of the pipe gets to 500 or 600 degrees, the wood roof, that has only 2" clearance, will catch fire I think before the silicone boot or RTV caulking fails.

    I cant go with this method anyway because of my metal roof.

    I guess if I wanted to be REALLY cautious, I could cut the cone off the metal flashing and stretch the silicone boot over that such that the silicone is more than 2" off the chimney, then pull that whole assembly over the chimney and then install the storm collar with RTV over the cone. That would probably satisfy Metal.

    It won't change the fact that if the outside of the chimney gets that hot, the building will burn down so I kinda wonder what's the point of doing that?

    Once I make a decision and get to install it, I will post pictures.

    unfortunately, with holiday travels, you will all have to wait because I won't be back to that cabin until mid January (which is breaking my heart).

    Thanks and happy holidays!
  16. Metal

    Metal Minister of Fire

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    Unless the flashing he uses is listed for use with the system, it, and the system as a whole, will not by UL Listed. Most if not all standard flashings for Class A (103HT) Pipe are ventilated and MUST be ventilated to pass the UL Testing, therefore unless you buy one of the expensive boot flashing kits (Selkirk sells one for ~$200) the only correct way to install it is as I stated.

    I’m done with you, you may go now.
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