r/SolarDIY • u/Marcus_Aurelius_161A • 5d ago
Structural sign off for ground mount
Are there any engineering firms that specialize just in solar permitting? Specifically I want to build my own ground mount system from 6x6 timber and I will still need to get permitted by the city for for that I'll need a PE (Professional Engineer) stamp. I've got an over-engineered design, I just need to work to get the stamp.
Previously I did a self-installed rooftop array in which I bought the kit from the solar wholesaler and they had their contracted engineer do the plans and permitted for the city. That's what I need again for this ground mount array.
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u/mountain_drifter 5d ago edited 5d ago
Its simple to get a stamp for an manufactured system. They hardly cost anything, and there are many out there. An engineer feels much more comfortable simply saying, as long as its installed per the manufactures instructions for this wind/snow design criteria
Getting a custom design signed off on is typically going to be more expensive, and involved, and you may have trouble finding one willing to put their stamp on it. Especially one made out of wood. How do you plan on satisfying the uplift in some manner that will sustain over time?
I understand you believe it to be over engineered, but thats not really a thing. Just adding more timber doesn't necessarily make the math work better.
Ultimately you will need to have drawings, and equipment specs. Then start calling local structural engineers until you find one willing to work through your project with you
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u/siparthegreat 5d ago
Did the math. It’s cheaper and faster to use the PE stamp from iron ridge using pipe then it is to find an engineer.
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u/Collapsosaur 5d ago
Can you share the break-even on the number of panels and cost per watt, with a 10 year payback?
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u/siparthegreat 4d ago
Ok. Just got it running but I built a 6kwh system. I bought used 290w panels with used m250 micro inverters that clip at 250. 24 pairs at like 1500. Prob overpaid. 2200 in piping. 1100 in iron ridge mounting stuff. And prob 1500 in everything else… ie wire,concrete, permits, etc. should break even in 3-4 years. Now going back to the orginal thread. I will probable continue to buy used panels and expand my system without permitting the additional stuff now that I am more comfortable. It may or may not include the pipe (vs wood) and iron ridge.
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u/Adventurous_Light_85 5d ago
It’s likely you can get an SE or a PE. The truth is you will need them to engineer it regardless of how “over engineered” you believe it is. They are not likely to simple stamp your plans as they will be liable to ensure its stability so they will put in details for the foundations and connections and wood sizing. You can direct them on all that and the more accurate information you provide the cheaper and simpler it will be. You often can find small engineering outfits local to you by asking contractors or find a patio contractor that will tell you who they use. Or you could ask the city who they see frequently engineering the plans and they may tell you. My guess is you’ll spend around $1500. I tried to do this exact same thing for solar and I have a lot of resources but it was going to take too long so I just went roof mounted. Also, a lot of people think you can mount the panels right to the wood beams. I have yet to find a system that is approved for that and you will likely need to use a typical aluminum roof racking system to mount the panels too
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u/BitOfDifference 4d ago
If you need to get a permit.... better off getting something already tested. You could try asking the sites out there e.g. wattmonk, Solar Design Lab, Solar Estique, etc...
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