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  • 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
    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.

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    • #3
      Re: Post base on EPDM

      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
      “It is difficult to get a man to understand something, when his salary depends on his not understanding it.” - Upton Sinclair

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      • #4
        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.

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        • #5
          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.

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          • #6
            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

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            • #7
              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

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              • #8
                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

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                • #9
                  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.

                  435bcdadb1f86d6dea904b8f494d3438.pdf
                  ============================================

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                  • #10
                    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!

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                    • #11
                      Re: Post base on EPDM

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

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                      • #12
                        Re: Post base on EPDM

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

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                        • #13
                          Re: Post base on EPDM

                          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
                          “It is difficult to get a man to understand something, when his salary depends on his not understanding it.” - Upton Sinclair

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                          • #14
                            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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