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  1. #1
    Join Date
    Feb 2005
    Location
    Gloucester MA
    Posts
    244

    Default Post base on EPDM

    Hello, I am looking for a post base/system designed to be installed on top of a EPDM roof for a 6x6. Ideally the base would be leak free, have some stand off for the wood post and be solidly attached with fastener to the structure below. I thought this would be an easy detail, but I am having a little trouble finding something for this application.

    6x6 Posts are meant to bear on flat roof (2nd floor) and support a 3rd floor deck above.

    Thanks for any ideas
    "I smell a lot of 'if' coming of this plan." -Jayne Cobb

  2. #2
    Join Date
    Aug 2004
    Location
    Fort Worth, Texas 76109
    Posts
    270

    Default Re: Post base on EPDM

    I don't know if there is a 100% fool proof way to doing what you are asking. As you know anytime you penetrate your roofing system, you are inviting water to penetrate it.

    What I did was similar to what you are suggesting, except I was using steel post/columns. My roof was also a tiled deck using a modified Schluter system.

    I took 2-1/2"x 20" long sq. tubing and bolted them to the 2x10 joist below allowing them to extend above the deck about 9". The roofing was turned up +/- 4" on the tubing and sealed as best possible. I then installed 3" steel post over the smaller tubing. I welded the steel post through holes that had been cut in the post +/- 6" above the finished tile and clear of the finished tile deck +/= 1". I covered the gap at the bottom with a metal shoe to trim it out.
    This is an over simplification but it is the best I can do. I hope it helps.

  3. #3
    Join Date
    Apr 2008
    Location
    SF Bay Area (East Bay)
    Posts
    2,014

    Default Re: Post base on EPDM

    Quote Originally Posted by Slaughter Construction Co View Post
    I took 2-1/2"x 20" long sq. tubing and bolted them to the 2x10 joist below allowing them to extend above the deck about 9". The roofing was turned up +/- 4" on the tubing and sealed as best possible. I then installed 3" steel post over the smaller tubing. I welded the steel post through holes that had been cut in the post +/- 6" above the finished tile and clear of the finished tile deck +/= 1". I covered the gap at the bottom with a metal shoe to trim it out.
    This is an over simplification but it is the best I can do. I hope it helps.
    If you used steel tubing, couldn't you use a regular round roof jack?

    kevin

  4. #4
    Join Date
    Aug 2004
    Location
    Fort Worth, Texas 76109
    Posts
    270

    Default Re: Post base on EPDM

    Kevin. First, the use of sq. tubing was an arch/esthetics decision. Second, I think it might be a little is easier to fasten/bolt something square to the joist and or fasten something else to it. If round works best for a particular situation, I've no problem with it.

    I was not trying to suggest any particular shape or material as I was just trying to describe a method that I had used when solving a similar problem that toobiloo was asking about. Bruce S.

  5. #5
    Join Date
    Jan 2009
    Location
    Danbury area of western CT
    Posts
    4,440

    Default Re: Post base on EPDM

    Some pics might help.
    If you use round galvanized pipe/tubing as a stand off pylon type fixture, you can use standard roof penetration boots used for plumbing vents. As close to water proof as you can get.

    Phil
    It's better to try and fail, than fail to try.

  6. #6
    Join Date
    Aug 2009
    Location
    St. Paul, MN & Northern WI
    Posts
    267

    Default Re: Post base on EPDM

    You really shouldn’t support a 6x6 post on top of a EPDM roofing, insulation, and roof sheathing, etc. sandwich. That’s just too much compressible material and furthermore, your bolts will still likely leak, because they move and are tough to seal. You have to cut through the roofing and then flash and waterproof that penetration like you would a plumbing vent or some such. In fact a round pipe through the roof might use the same rubber boot system they use on a plumbing vent pipe. Years ago the solution at these penetrations was a pitch pocket. The bigger question is that you are proposing to support and upper deck on a number of 6x6 posts, which concentrate the deck loads at a few points. Then you are thinking these post will bear on an existing roof joist below. How does that work? One would assume that those joists were not over designed by the original builder, thinking/knowing that you would have a pipe dream some years later. Those post loads have to be taken down to the foundation, and you have to determine, or make that load path, without allowing the flat roof to leak.
    Dick Hackbarth, PE
    RWH&AI, Consulting Engineers

  7. #7
    Join Date
    Feb 2005
    Location
    Gloucester MA
    Posts
    244

    Default Re: Post base on EPDM

    Thanks for the ideas. Pitch pockets seams like it would eventually rot the bottom of the post?
    I am leaning towards a stainless stand of sealed to roof.
    I did plan enough ahead to put solid bearing at the areas i need it (I used plywood at bearing points instead of the recovery board. Construction is post over post to the ground, so my load path is straight forward.

    Thanks
    Tobias
    "I smell a lot of 'if' coming of this plan." -Jayne Cobb

  8. #8
    Join Date
    Jul 2006
    Location
    Portland, OR
    Posts
    2,396

    Default Re: Post base on EPDM

    ON the roofing simply WILL NOT WORK.
    THROUGH the roofing, if the post is to be left exposed WILL NOT WORK.
    THROUGH the roofing, with an EPDM base detail, the post fully wrapped with a top quality WRB, then clad with a finish material, is the ONLY way this will work

  9. #9
    Join Date
    Jun 2004
    Location
    Houston & Washington Texas
    Posts
    11,892

    Default Re: Post base on EPDM

    This is how we do it, see diagram. We typically build up 2" or so with stone, so we have to allow for mud/stone.

    Post Detail.pdf

  10. #10
    Join Date
    Jan 2007
    Location
    Louisville, KY
    Posts
    3,753

    Default Re: Post base on EPDM

    If a wood post is necessary I would create something out of steel to act a pedestal of some sort. Then you could mount a post on top of it properly.

    Depending on how you did the steel pedestal would determine whether a pitch pocket or field flashing would work.

    Like others said. You can't sit it on top of epdm and insulation.
    Louisville Exteriors
    Professional Installers of:
    Siding | Replacement Windows | Roofing | Hand Rails | Gutters | And More!

  11. #11
    Join Date
    Jun 2004
    Location
    Des Moines, Iowa
    Posts
    3,764

    Default Re: Post base on EPDM

    here are a couple of pictures of pitch pockets.
    Attached Images Attached Images
    Mark Parlee
    BESI(building envelope science institute) Envelope Inspector
    EDI Certified EIFS Inspector/Moisture Analyst/Quality Control/Building Envelope II
    Level one thermagrapher (Snell Training)
    www.thebuildingconsultant.com
    www.parleebuilders.com
    You build to code, code is the minimum to pass this test. Congratulations your grade is a D-

  12. #12
    Join Date
    Nov 2005
    Location
    VA
    Posts
    1,405

    Default Re: Post base on EPDM

    NW Architect has the best idea. I have done it that way a few times.

  13. #13
    Join Date
    Apr 2008
    Location
    SF Bay Area (East Bay)
    Posts
    2,014

    Default Re: Post base on EPDM

    Quote Originally Posted by toobiloo View Post
    Construction is post over post to the ground, so my load path is straight forward.
    That covers the vertical load- what is resisting the lateral and rotational forces generated when large marge leans on the railing? Or are these posts/railings simply decorative?

    k

  14. #14
    Join Date
    Jul 2006
    Location
    Portland, OR
    Posts
    2,396

    Default Re: Post base on EPDM

    #11, photo 1: Good example of why exposed posts do not work. The pitch pocket is sealed to the outside of the base hardware. The hardware is just butted to the side of the post. Water enters between hardware and post.

    Even if pitch pocket covered the hardware, checks eventually open up in the wood and allow a water entry path behind the pitch, or any other flashing.

    Even Allen's detail at #11 is vulnerable unless the post just site on the pin. If the post has to be tied down for uplift, there is a bolt or two through the wood and into the pin/plate. Water can enter there and bypass the flashing

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