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How much concrete footer do I need for a given wind load?

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  • How much concrete footer do I need for a given wind load?

    This structure will hopefully be installed in the fall. the biggest wind load would be on the south North side which is about 65' long and 10.5' tall. made of treated plywood probably 5/8" thickness.
    Will be in Orlando Florida, must be designed for 3 second wind load of 110mph winds.

    how much concrete do I need to pour? Maybe I just have to ask my local building codes people?

    Here is a photo.

  • #2

    Re: How much concrete footer do I need for a given wind load?

    Re: How much concrete footer do I need for a given wind load?

    You absolutely have to talk with the local inspector. Ultimately that is who will say "yea" or "nay" to your plan. Even if you have a certified engineer design the foundation the inspector has the final say. Asking him/her is the fastest way to get the 100% correct answer for your area. They will probably also give you specs for hurricane ties as well.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

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    • #3

      Re: How much concrete footer do I need for a given wind load?

      Re: How much concrete footer do I need for a given wind load?

      I don't know--but you may also run into problems if the "roof" (panels) are less than ~8' off the ground (or whatever the exact code is) because of the possibility of somebody standing in wet grass and touching a "defective" panel (rated up to 600 VDC above ground). Unless you put a locked fence around the structure (which you would not want to do--I presume).

      -Bill
      20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

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      • #4

        Re: How much concrete footer do I need for a given wind load?

        Re: How much concrete footer do I need for a given wind load?

        OK, thanks I just wrote an email to the permit dept.

        Comment


        • #5

          Re: How much concrete footer do I need for a given wind load?

          Re: How much concrete footer do I need for a given wind load?

          Well the building codes dept did NOT respond to my email and instead said it would be easier to call me and answer my questions which I thougth was lame.

          Conversation went like this:
          ME: Is a fence is required around the PV?
          HIM: Yes due to high voltage
          ME:how tall does it need to be?
          HIM:It can't be over 6 feet.
          ME: OK, but that' not really what I asked what is the minimum height it needs to be.
          HIM: Typically 4 feet, but with such high voltage you should probably make it 6.
          ME: What do you mean "probably?" I don't want to make a six foot tall fence and then find out it needs to be a different height.
          HIM: Well we've never had anyone make such a big solar PV system so you'd have to submit plans first and get them approved.

          Any other question I asked him about wind loads was basically a useless response like I'd have to get a professional engineer to submit wind load requirements.

          Even a simple question like what type of conduit is required? got me an answer like look it up in the NEC book, I'd hate to misinform you.

          The problem is hiring an engineer is not really economically viable, I might as well buy a unirac system that is already tested.

          I'll probably try to build a shed and then just mount the units on top of it. He seemed to think that was fine and would avoid the whole wind load issue, didn't really make sense to me since there are still wind loads on the panels, just not as much.

          Only problem is I"ll have to call it Solar PV mounting structure since the HOA doesn't allow sheds.

          I wish I could just over engineer the thing instead of having to pay someone to do a bunch of white collar desing work to tell me that I can get away with the lightest metal possible.

          Comment


          • #6

            Re: How much concrete footer do I need for a given wind load?

            Re: How much concrete footer do I need for a given wind load?

            Thank you for once again making me ever so glad I no longer have to deal with such people!

            You might also notice that's another reason why we don't hand out building code advice around here; what's right for one locale is not right for another, and even one that is can be wrong if the half-wit bureaucrat in charge says so.

            Mock conversation with Building Inspector:
            RE: Are you a blinking idiot?
            BI: No. Yes. Maybe. It all depends. You'd better get a professional psychiatrist to assess that.
            1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

            Ohm's Law: Amps = Volts / Ohms
            Power Formula: Watts = Volts * Amps

            Comment


            • #7

              Re: How much concrete footer do I need for a given wind load?

              Re: How much concrete footer do I need for a given wind load?

              Hi RE, I see you did not ask the concrete question..
              IMHO, yes the inspectors are quite vague at times but they normally do concede/defer to a P.Eng. especially to plans with a stamp/seal on them. The seal transfers the legal responsibility to the PE.
              You being in a HIGH wind area , to me, would make it worthwhile, especially to meet that "must be designed for 3 second wind load of 110mph winds" requirement.

              ej
              100% Off Grid @ 51* 46' N lat 124* 44' W long

              New House system: coming - 2 arrays @ 2240W
              CL150&Epanel 4 @140 W 12v PVs , 24V C&D AT-15P AGM @ 950Ah, Linksys wet54g - WiFi bridge, Cotek ST1500W inverter,TBS Omni-charger 30a-24v, ,
              + CL150 4 @140W 12 V panels, 24V C&D AT-15P AGM @ 950Ah
              Honda Eu3000is,Eu1000is

              Guest cabin system: 3 - 70W panels to BS 2000e CC, with 2 - 100 ah 12v SAFT wet NiCd's , 600W TSW Inverter

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              • #8

                Re: How much concrete footer do I need for a given wind load?

                Re: How much concrete footer do I need for a given wind load?

                You are required to have plans stamped by a state licensed professional engineer. This isn't a DIY calculation that this website or the building department would provide.

                This is no code requirements for fencing of ground mounted PV in the State of Florida, and in my county there is no local requirement either.

                You have to find a PE, and submit plans.

                For a roof mount system, it cost me and people I have referred about 250.00 for the review and approved/stamped plans that in my case I did in MS-Paint. For your building it will be allot more as you now have a structure that must be reviewed to meet hurricane codes on top of whatever is need for the PV support and uplift requirements, detailed blue prints will be required for construction which for the permit will require the PE signoff.
                www.solar-guppy.com
                sigpic

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                • #9

                  Re: How much concrete footer do I need for a given wind load?

                  Re: How much concrete footer do I need for a given wind load?

                  thanks solar guppy! you're right, which is why I'm looking to purchase a solar carport that is preengineered with drawings/windload calcs, etc, which I can buy and DIY install.

                  It will cost more than the aluminum structure I was going to build which was wayy over engineered with solid 1.5" square posts, but less than having to hire a PE and get them to approved my custom design.

                  Peace, Rolland

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                  • #10

                    Re: How much concrete footer do I need for a given wind load?

                    Re: How much concrete footer do I need for a given wind load?

                    You'll need a Florida PE no mater what ... There is no short cuts for this
                    www.solar-guppy.com
                    sigpic

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                    • #11

                      Re: How much concrete footer do I need for a given wind load?

                      Re: How much concrete footer do I need for a given wind load?

                      This may help point you in the right direction.


                      http://signcost.org/winds.html

                      HTH

                      Square footage of exposed area, height, then shear factor of the uprights, type of soil and a good bit of overbuild. =)

                      Comment


                      • #12

                        Re: How much concrete footer do I need for a given wind load?

                        Re: How much concrete footer do I need for a given wind load?

                        I was playing around with this yesterday, thinking about building a solar tracker.

                        I was amazed how much wind load a 12x10 area has.

                        But my area is rated at 110 mph.
                        Last edited by bluetick; July 8th, 2011, 13:28.

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                        • #13

                          Re: How much concrete footer do I need for a given wind load?

                          Re: How much concrete footer do I need for a given wind load?

                          Even the professionals get it wrong once in a while:

                          Large Windmill collapse in NH

                          -Bill
                          20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

                          Comment


                          • #14

                            Re: How much concrete footer do I need for a given wind load?

                            Re: How much concrete footer do I need for a given wind load?

                            got a quote back from schletter.us
                            standard ground mount was a little less than 3 yd3 of concrete
                            However car port design raised that to 10 yd3 of concrete!

                            Comment


                            • #15

                              Re: How much concrete footer do I need for a given wind load?

                              Re: How much concrete footer do I need for a given wind load?

                              Call a steel building company. That industry is very competitive and will willingly whip out at least a modification of their standard building for what you want that is engineered for your location. Buy that or something similar. Pretty hard to beat the cost effectiveness of a steel structure. Your permit people will love it. They don't usually do the foundation design as part of the building design though. But I never heard of a conc. slab getting picked up by a hurricane.
                              2.7kW Trina/Xantrex GT, 3.7kW Trina/SolarEdge, 3kW CSI/SMA GT, Solar well pump on 6, 25yr old Holeck 48W modules. Toyota SR5 converted to 108V EV. Prius w/Enginer PHEV conversion. BSEE, R11-residential, NABCEP, SunnyPro, >800kW installed
                              "Faced with the choice between changing one's mind and proving that there is no need to do so, almost everyone gets busy on the proof." - John Kenneth Galbraith

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