HomeMade Mount Questions

marsofoldmarsofold Solar Expert Posts: 45 ✭✭
I've seen some estimates online of $7/watt for an installer to mount a solar system. Not sure what these estimates all include. I already have the panels, wiring with MC4 connectors, charge controller, batteries, battery box, and inverters. I think that I could build a mount for around $800 using aluminum Unistrut rails and a wood frame. Would an installer charge over $2000 to supply the labor, rails, standoffs, and misc stuff? My array would only be about 9.9ft x 9.9ft. I can't see paying someone much over $1200 labor for a days work.

If I do it myself would the general method be drilling pilot holes, filling them with silicone, than screwing in a bolt, tarring over the plywood around the bolt, then putting in a piece of metal flashing (with a center hole) tarred underneath. The opposing tarred surfaces would adhere. Then putting a nut over the bolt to hold down the flashing. Then using masking tape to hold down the flashing edges and tarring heavily all over that. That would be my approach to roof penetrations. Would it leak? My brother-in-law owns a construction company, has built lots of houses, thinks it wouldn't leak. But I'm less confident. Opinions?

Since panels have side holes for mounting, would it be practical just to bolt them down to aluminum Unistrut rails on a wood frame on standoffs attached to my roof penetration bolts? Seems the simplest way to me. Or would conventional clamps be preferred? I would feel better about bolting panels down, but since everyone seems to go for clamps is there a significant advantage to them?

Thanks for any advice offered...


  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: HomeMade Mount Questions

    $7/ watt was probably for buying everything, and doing everything from start to finish.

    Your roofing plan sounds fine.

    The clamps are just quicker installation.

    You can bolt things down if you prefer that way, just takes more time
  • FrxddyFrxddy Solar Expert Posts: 113 ✭✭✭✭
    Re: HomeMade Mount Questions

    I'd shy away from using wood. Even pressure treated can deteriorate in a matter of years. Asking wood to last the life of the panels is asking a lot.

    Flashing is good. It's hard to comment without seeing your actual idea. I put it this way: Any goopy stuff (tar, silicone, etc) should be incidental. If you used none, the flashing should be waterproof by itself. The goopy stuff is just a help to help fend off the occasional wind driven rain.

    On my 30 panel installation I saved almost two grand by building my own racks, but I did do it myself. As for hiring it done, I'd look to hire any competent roofer or mechanic.
  • solarixsolarix Solar Expert Posts: 713 ✭✭
    Re: HomeMade Mount Questions

    At a meeting involving most of the installers around here, the question was asked:
    What kind of worker would you like to hire?
    A) A newly trained young certified solar installer.
    B) An experienced, out of work electrician that wants to learn solar.

    Someone spoke up and answered:
    C) An out of work roofer, we'll teach him everything else.
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: HomeMade Mount Questions

    I've mounted my own solar panels use either homemade brackets (for the smaller panels) or purchased brackets (for the larger ones). In both cases, the brackets were aluminum. I will not put any wood outside here in FL. It'll rot sooner than later.

    The bolts & washers are stainless steel. Purchased at my local Ace Hardware. I buy this stuff by the box.


    Drill a pilot hole through the shingles, and into the plywood below.


    Fill the hole with 100% silicone caulk (do NOT use latex caulk as it will dissolve in rain).


    Drive the bolt home, but do not overtighten & strip the wood.


    The extra caulk will ooze out around the washer. Spread it around the bolt & washer.


    The larger 130W & 135W panels are mounted using Unirac #990009 RV Z-brackets. Pic at link. 4 stainless steel bolts & washers per foot. Raises it off the roof enough for airflow, but keeps it low profile so winds can't get underneath it during a tropical storm, and potentially a hurricane. A big enough storm will take them anyway, but better to keep them as low as possible.


    Zero leaks in the several years they've been up there. Not even a slight weep from looking at the underside of the plywood... despite the FL monsoons!
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: HomeMade Mount Questions

    those pvs are way to close to the roof surface. those pvs are super heating because of little airflow underneath.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: HomeMade Mount Questions

    I'm one of those who lags brackets to roofs. But the most important step is to check and make sure there's roof to lag it to. Putting a 2" lag bolt into 3/4" plywood (or 3/8" - which they allow up here) won't do. Make sure there's sufficient structure in the roof to handle the panels. Since this is forestry country, most of the cabins have 2" thick "sheathing"; no worries. But always check.

    Got to agree with Niel about the lack of space under the panels; should have at least 4" in my opinion. Up here you need 6" at the bottom of the tiltable mount or else you're in trouble from the wonderful wacky weather (hail yesterday - it's only August).

    So there you have another factor: adapting mounting practices to local conditions. We don't have to worry much about wind loads, but in Florida ... WHOOSH! :cry:

    P.S.: That silicon Robert is using - is it UV grade?
  • RCinFLARCinFLA Solar Expert Posts: 1,334 ✭✭✭
    Re: HomeMade Mount Questions

    Consider schedule 80 PVC pipe for the frame. 1 1/4" or 1 1/2" pipe. Very low cost, and very strong frame. Can be painted with latex paint for additional UV protection.

    There are several options for the roof mount flange. There are floor mount flanges and closet flanges.

  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: HomeMade Mount Questions
    niel wrote: »
    those pvs are way to close to the roof surface. those pvs are super heating because of little airflow underneath.

    Might be true for the few 15W Harbor Freight panels, but since they're operating attic fans (etc), not a big deal.

    Most of my energy comes from the larger Kyocera 130W & 135W panels. Those do sit higher off the deck. IIRC, the Z-brackets raise the frames up an inch, and the frames are ~2" thick.


    Have to make some compromises here. Yes, having the panels elevated would certainly improve cooling/efficiency, but having them end up in the next country - not so good!

    My panels survived Tropical Storm Fay a couple of years ago. Hurricane season lasts 6 months per year, and I'm 10 minutes from the beach in central E. coast of FL.

    This was my previous house in 1995, when Hurricane Erin (only a Cat I) thumped our house.


    In 2004, we had two back to back hurricanes... This is my present house:

    The first storm ripped off many of the shingles. I put on a 30W roofing felt patch.


    A couple weeks later, a second hurricane ripped off another patch of shingles, but left the patch.


    So you can see why I'm gunshy of mounting ANYTHING much above the roof level.

  • snuffysnuffy Solar Expert Posts: 72 ✭✭✭✭
    Re: HomeMade Mount Questions

    I don't like the idea of mounting panels on the roof so I did this.
    Attachment not found.
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: HomeMade Mount Questions

    So there you have another factor: adapting mounting practices to local conditions. We don't have to worry much about wind loads, but in Florida ... WHOOSH! :cry:

    P.S.: That silicon Robert is using - is it UV grade?

    What I haven't done yet, but plan on measuring, is the temperature of the panels. Front side, back side, roof temp beside a panel, and under a panel. Curious to see what the thermal characteristics are under these less than ideal conditions.

    My small 880W array still not doing too bad, even on a hot day:


    The caulk I use is 100% silicone rubber. The specs say:

    · All-purpose, indoor/outdoor use
    · Watertight seal
    · Long-lasting flexibility
    · Minimal shrinkage
    · 50 year durability guarantee

    DAP® 100% Silicone Sealant Rubber Sealant is an all-purpose, one component, acetoxy cure sealant ideal for indoor/outdoor use. It provides a watertight, flexible seal that won’t crack, crumble or shrink. Once cured, it is unaffected by temperature extremes (-40°F to 400°F). It meets ASTM Specification C 920, Class 25, Type S, Grade NS and has a 50 year durability guarantee.

    More blah blah here: http://www.dap.com/docs/tech/00000683.pdf Bottom line, I've been using this stuff for years, no issues.
  • marsofoldmarsofold Solar Expert Posts: 45 ✭✭
    Re: HomeMade Mount Questions

    OK, lots of good replies. I'm looking at doing five roof penetrations forming a 8' x 8' square with the fifth penetration at the center. 6" Pro-solar FastJacks to do the penetrations since they only need one hole. Since the array will be 10' x10'' & held by aluminum Unistrut, will these five penetrations be enough to hold it securely down from the wind? I live in a valley within Lancaster County, PA. Thank you guys for all of your insightful help...
  • PhotowhitPhotowhit Solar Expert Posts: 5,422 ✭✭✭✭✭
    Re: HomeMade Mount Questions

    I just wanted to defend pressure treated wood, though why you would use it for a roof mount, I have no clue.

    In the battery box I built, I used a 3/4 4x8 sheet of pressure treated plywood, that I had been saving, I 'found' it while doing a lot cleanup on one of our camping lot that had been left abandon and we got it back from the original owners, I came in and raked leaves picked up rubbish, mowed... I found this sheet of plywood laying on the ground under decaying leaves which had become dirt, I promise I did not know it was there until I was racking.

    I hosed it off and kept it arround until I built my box and recycled it. I'm sure it is 15 years old at least and perhaps made back when they put asenic and alsorts of good poisons into the wood, but I got to tell you, I have an 1100lb battery on it now and slid it across that old surface with no problems, and have no worries about it.

    I built my free standing frame from pressure treated lumber and I think it'll be fine, a tornado will take out most anything, it's withstood 60 mile and hour straight line winds. Missouri's finest.

    I lived in Forida, and understand it's extreams, use to love watching the national Sears(?) termite home service with warranty except in Florida...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • marsofoldmarsofold Solar Expert Posts: 45 ✭✭
    Re: HomeMade Mount Questions

    OK gonna drop the wood and go for all aluminum. Ordered nine 6" FastJacks to do nine penetrations for better span support. Can anyone tell me what is the best type of conical flashing to use with these 6" high penetrations? The best that I can come up with is to use polymer/rubber collars attached to aluminum flashing. I'd prefer to use an all metal solution to avoid ozone rubber degradation, but don't want to pay $50 per penetration. Or worst of all to leak. Any help on this would be much appreciated...
  • mike95490mike95490 Solar Expert Posts: 9,099 ✭✭✭✭✭
    Re: HomeMade Mount Questions

    I asked my roofer to use regular "Plumbing Roof Jacks" that are used around vent pipes. Tin (or something) with a polymer gasket.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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