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  1. #1
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    Default Can i limit the number of roof plumbing vent openings through the roof to one

    I am not sure if this is the correct forum for a serious diy remodeler to ask questions. If it isn't let me know and I will go back to just reading> I have learned a lot that way already.

    I am converting a barn into living space working under the 2009 IBC. My question is it possible to tie all the plumbing vents together to limit the holes through the roof to just one for the vent pipes.

    I will have two bathrooms, a kitchen and laundry room. If it can be done to code any tips, or caveats would be very welcome.

    Thank you Jim Bunton

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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Not sure about IL, normally 1 vent must extend through the roof covering. Pipe diameter must be 3" minimum and extend 6" above the roof covering or 6 inches above the anticipated snow load, whichever is greater.
    IRC is normally the standard for one & two family or residential construction, IBC for commercial. Dont have a 2009 of either on hand at the moment, the above is taken from the 2006 IRC.

    Alton Darty
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  3. #3
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by Alton Darty View Post
    Not sure about IL, normally 1 vent must extend through the roof covering. Pipe diameter must be 3" minimum and extend 6" above the roof covering or 6 inches above the anticipated snow load, whichever is greater.
    IRC is normally the standard for one & two family or residential construction, IBC for commercial. Dont have a 2009 of either on hand at the moment, the above is taken from the 2006 IRC.
    Thank you for your response Alton. I meant the 2009 IRC .


  4. #4
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by Jim Bunton View Post
    I am not sure if this is the correct forum for a serious diy remodeler to ask questions. If it isn't let me know and I will go back to just reading> I have learned a lot that way already.
    I am converting a barn into living space working under the 2009 IBC. My question is it possible to tie all the plumbing vents together to limit the holes through the roof to just one for the vent pipes.
    I will have two bathrooms, a kitchen and laundry room. If it can be done to code any tips, or caveats would be very welcome.
    Thank you Jim Bunton
    Hi Jim,

    It sounds like you can do it, but it will be necessary to size the pipe correctly and provide the necessary slope (as well as take in the considerations Alton posted). If you don't know how to calculate vent sizes, you should be able to pick up a CodeCheck Plumbing or Complete. It has tables for supply, drain and vent sizing.

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  5. #5
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Possible, probably. The best option, probably not.
    It will really depend on distances and pipe sizing. Also you need to increase the size of the vent pipe one size just before exiting through the roof.
    I've dealt with jobs where this has been done. Unless all the fixtures are essentially on a single vertical tier it tends to be a waste of pipe making horizontal runs over to that 1 vent stack. Going straight up from your fixture riser tends to be a better option.
    If there is some aesthetic issue then that just comes down to the old 'form of function' debate. If its a concern about roof leak potential then you need to hire a real roofer or read the NRCA manuals not some schmuck who tells you 'yes I do roofing, uh'.

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  6. #6
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by Markus Keller View Post
    Possible, probably. The best option, probably not.
    It will really depend on distances and pipe sizing. Also you need to increase the size of the vent pipe one size just before exiting through the roof.
    I've dealt with jobs where this has been done. Unless all the fixtures are essentially on a single vertical tier it tends to be a waste of pipe making horizontal runs over to that 1 vent stack. Going straight up from your fixture riser tends to be a better option.
    If there is some aesthetic issue then that just comes down to the old 'form of function' debate. If its a concern about roof leak potential then you need to hire a real roofer or read the NRCA manuals not some schmuck who tells you 'yes I do roofing, uh'.
    I have a seventy year old "slate" roof that doesn't leak and I think the fewer holes the better my chances are of it continuing not to leak. My house has the same material and just passed the 100 year mark.

    My thought was to run a 3" or 4'"pipe down the side of the house that contains most of the plumbing and tying into it as it passes by the various fixtures. I will maintain the proper slope, and size the various fixtures according to code.

    Does this sound correct?

    Jim

    Last edited by Jim Bunton; 10-19-2016 at 11:16 PM.

  7. #7
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Based on the probable fixture count you'd need at least a 3" vent stack which would need to be increased to 4" before it leaves the interior.
    When you say 'down the side of the house' I hope that means at the interior. Unless you are all the way down in southern IL running the vent stack along the outside causes other issues.

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  8. #8
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by Markus Keller View Post
    Based on the probable fixture count you'd need at least a 3" vent stack which would need to be increased to 4" before it leaves the interior.
    When you say 'down the side of the house' I hope that means at the interior. Unless you are all the way down in southern IL running the vent stack along the outside causes other issues.
    Markus,

    He could insulate around the stack, box it in, and cover it with sheathing/siding the same (or similar) as the building, couldn't he?

    That should resolve the issues with the stack "outside" the thermal envelope (freezing) and "outside" the structural envelope (wind, snow, etc) - the stack would now be "inside" both.

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  9. #9
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Yes he could probably do that but not really the norm around here. I'd have to look up if there is a Code restriction on that because its just not a common installation anymore. Once in a while I'll run into an old cast stack going up the outside of a house from way back when but that's about it.

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  10. #10
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by Markus Keller View Post
    Based on the probable fixture count you'd need at least a 3" vent stack which would need to be increased to 4" before it leaves the interior.
    When you say 'down the side of the house' I hope that means at the interior. Unless you are all the way down in southern IL running the vent stack along the outside causes other issues.
    I am talking about in the unheated attic (hayloft). Is freezing an issue? If it is could I insulate,and heat trace the 3" pipe

    Jim


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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by Jim Bunton View Post
    I am not sure if this is the correct forum for a serious diy remodeler to ask questions. If it isn't let me know and I will go back to just reading> I have learned a lot that way already.

    I am converting a barn into living space working under the 2009 IBC. My question is it possible to tie all the plumbing vents together to limit the holes through the roof to just one for the vent pipes.

    I will have two bathrooms, a kitchen and laundry room. If it can be done to code any tips, or caveats would be very welcome.

    Thank you Jim Bunton
    Jim, from my understanding no.
    Please expand further through.
    How many main waste drains are there?

    The IPC states; 903.1
    903.1 Required vent extension. The vent system serving "each building drain" shall have at least one vent pipe that extends tothe outdoors


    - - - Updated - - -

    Quote Originally Posted by Jim Bunton View Post
    I am talking about in the unheated attic (hayloft). Is freezing an issue? If it is could I insulate,and heat trace the 3" pipe

    Jim
    No issue. You do not have to insulate the pipe.

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  12. #12
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by ROBERT YOUNG View Post
    Jim, from my understanding no.
    Please expand further through.
    How many main waste drains are there?

    The IPC states; 903.1
    903.1 Required vent extension. The vent system serving "each building drain" shall have at least one vent pipe that extends tothe outdoors



    No issue. You do not have to insulate the pipe.
    I am not sure what you mean by main waste drain. I assume it means the line carrying the waste out of the house to the septic tank. If this is correct I have one. Jim


  13. #13
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by Jim Bunton View Post
    I am not sure if this is the correct forum for a serious diy remodeler to ask questions. If it isn't let me know and I will go back to just reading> I have learned a lot that way already.

    I am converting a barn into living space working under the 2009 IBC. My question is it possible to tie all the plumbing vents together to limit the holes through the roof to just one for the vent pipes.

    I will have two bathrooms, a kitchen and laundry room. If it can be done to code any tips, or caveats would be very welcome.

    Thank you Jim Bunton

    Jim, sorry for any confusion on my part.
    Also, I did not realize you had a styptic system although I do not know if that makes a difference.

    Lets work on the premise, the house was waste vented/plumbed correctly. Therefore, the need for two vent stacks.
    One main stack for the two bathrooms and kitchen, and the other a secondary stack for the laundry room added later that is far enough away from the main wet stack.

    dwv.JPG

    Venting distance is likely why you require a secondary stack.

    Why worry about holes in the roof? If the roof is properly covered the likelihood of a leak at the stack is few and far between.

    Robert Young's Montreal Home Inspection Services Inc.
    Call (514) 489-1887 or (514) 441-3732
    Our Motto; Putting information where you need it most, "In your hands.

  14. #14
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Quote Originally Posted by ROBERT YOUNG View Post
    Venting distance is likely why you require a secondary stack.
    This could be addressed by installing an AAV on the secondary vent (AAV's are allowed in most areas, not sure if Illinois still prohibits them or not).

    That would leave the required "at least one" vent to vent to the outdoors.

    Why worry about holes in the roof? If the roof is properly covered the likelihood of a leak at the stack is few and far between.
    If a roof is not leaking, why potentially "cause" it to leak? Typically, roofs leak at "penetrations" (vents, exhausts, flashings at head walls/valleys/side walls/parapets/etc) ... a "penetration" is anything that disrupts the plane of the roof covering and causes the roof covering to be breached and go around the items (plumbing vents, dryer vents, etc) or stop/start again (any flashing for a head wall, side wall, valley, etc).

    By installing the stack up the exterior side of the house/barn, then enclosing the stack as previously described, the stack is no longer "outside", the stack is now "inside" just as though it was enclosed within the wall (which it now is).

    The code allows plumbing vents to terminate out through a wall (albeit that is not the most effective venting - through the roof is, but codes are minimum and that would meet the minimum code ... and to remind all - code is not not good/better/best practices, only minimum requirements).

    From the IRC: P3103.6 Extension through the wall.

    However, in Illinois ... as I recall, the IRC does not apply, Illinois has its own codes from the past and driven by unions (not saying that unions are a bad thing, but unions can create and maintain "overkill" for some things, however, unions are a result of "overkill" by business in the first place, so were extremely necessary at the time, and to some extent remain so).

    Jerry Peck, Construction / Litigation Consultant
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  15. #15
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    First, I'd agree with the premise of reducing roof penetrations when you can do so easily, and that's especially true for a slate roof -- it's difficult to find competent slate roofers, and they're expensive. And, it's a delicate roofing system, so the less time anyone is on the roof the better (the flip side being that it will last decades longer than composite shingles).

    Next: what you need re: vents depends on the fixtures you're venting (specifically, if you are an IRC area, "fixture units" defined by Table P3004.1). For "two bathrooms, a kitchen and laundry room"
    full-bath groups worst case: 6 units
    kitchen: 2 units
    laundry: 3 units
    All this leaves you well under the 24 units a 3" vent (your most likely size) can take through the roof. You have to slope things properly: remember that vents drain away from the stack when they join it (otherwise: they drain toward the fixtures they are venting). Hopefully that's obvious. Pipe sizing will depends first on the required drain pipe size (3" I suspect: vents must be no less than 1/2 that, with at least one 3" all the way through the roof): a developed length of pipe runs of greater than 40' requires bumping up a pipe size. Obviously I'm not walking through everything you'll need for planning your drain lines, etc, so don't imagine I am. These are just the basics.

    It looks to me like most of IL does use the ICC codes:
    http://www.iccsafe.org/about-icc/gov.../map/illinois/

    Around here you don't ever insulate vent pipes, but I'm in the mid-Atlantic. P3101.4 says that in areas with 97.5% value for outside design temp <= 0 F, you have to insulate vent pipes that are outside: that's almost everywhere in IL. In such areas, every vent extension through a wall or roof must be 3" or more (P3103.2): the origin of the "one size up" concept, I think (that doesn't appear in the code otherwise, afaik).

    As noted before, you may be able to use air admittance valves, and that might save you some trouble. It might be easiest to put them in the attic (assuming you have one), at least 6" above the insulation if the ceiling is insulated (vs. roof): they must be accessable and in a "ventilated space" (p3114.5).

    Good luck.


  16. #16
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    Default Re: Can i limit the number of roof plumbing vent openings through the roof to one

    Thank you one and all I got a lot of useful advise and think I know how to proceed. I will talk to the county now that I have a plan. They are not the best at helping but they are good at telling you what you did wrong in your plan and how to corect it.

    Jim


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