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DIY ground mount - laminated posts..

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42OhmsPA

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I had another one of my bright ideas...

I'm considering using 3 2x6's glued and screwed together with the grain alternating to make my posts for the mount.

Why is this a bad idea?
 
Yea, they would be slightly more expensive than buying 4x6 but you'd gain an extra inch of material laminating the 3 2x6.

My biggest concern is water getting between the boards if the construction adhesive fails.

I got the idea when I was leaving for work this morning and saw the 3x 2x10 beam I built for my deck years ago.
 
If ground rated pressure treated it should last longer than larger cross section of treated timber since the chemicals can penetrate further into the wood. That what I read regarding poll barn construction.
 
Glue-lam will always be stronger and last longer.
And if you put it together close to its final location.
It's only back breaking for a short period. lol
 
Probably doesn't matter for your application, but the way lumber is graded will result in your laminated beam having a lower structural rating. It's easiest to just think about knots. In a #2 graded 2x6 the knots have to be a certain distance apart. If you glue two of those 2x6 together,you could end up with knots right on top of each other. That would disqualify a 4x6 being rated #2 because the knots are too close. If you buy a beam that's commercially laminated, this is all taken into account. I like making laminated beams because it's easier to get long lengths that are straight because I can put the bows against each other to pull both boards straight.
 
Lumber is a very poor choice for racking, all wood will warp and twist over time in the elements which stresses the framing of the solar panels which will lead to failures. Yes it can be built well and look good at first but time will always win.
 
timselectric said:
Glue-lam will always be stronger and last longer.
And if you put it together close to its final location.
It's only back breaking for a short period. lol
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Thank you. That's a great point about lighter weight / easier to handle. I don't miss the 6x6s and 2x12s I used building my deck years ago.
MarkSolar said:
Probably doesn't matter for your application, but the way lumber is graded will result in your laminated beam having a lower structural rating. It's easiest to just think about knots. In a #2 graded 2x6 the knots have to be a certain distance apart. If you glue two of those 2x6 together,you could end up with knots right on top of each other. That would disqualify a 4x6 being rated #2 because the knots are too close. If you buy a beam that's commercially laminated, this is all taken into account. I like making laminated beams because it's easier to get long lengths that are straight because I can put the bows against each other to pull both boards straight.
Click to expand...
That's a great point about the knots. I'm meticulous and would make sure none overlap.
I also found it very easy to orient the crown when I built the 2x10 beam years ago. It's still holding up great and shows no signs of age.
Solar Guppy said:
Lumber is a very poor choice for racking, all wood will warp and twist over time in the elements which stresses the framing of the solar panels which will lead to failures. Yes it can be built well and look good at first but time will always win.
Click to expand...
Agreed 100%.
This will only be a short term (3-5yrs) setup at the max. I've also considering using pallet racking due to another diy build on here.
I'll also be mounting the panels on 12ga strut to help negate some of the warping and twisting.
 
I do things simply and cheaply, especially with ground mounts as I have not had one in the same position for more than a year. Have withstood a few bouts of 80-90mph winds. But again, not considered permanent.
 

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HalfBaked said:
I do things simply and cheaply, especially with ground mounts as I have not had one in the same position for more than a year. Have withstood a few bouts of 80-90mph winds. But again, not considered permanent.
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I love the KISS method. Like almost everything else I do, I'm sure I'm over thinking this drastically.
If the price of galvanized pipe wasn't f'd this thing would have been built already.
 
Well I ended up going hybrid... Initially I had laminated 3 posts, the 2 outer and the center, then I decided it wouldn't be strong enough so I added 2 more 4x6's.
All in all I'm happy. There are a few minor imperfections but I can't complain for working alone, next time I'm phoning a friend for help...
I still have to add more diagonal bracing and I'm going to anchor the tall posts to the poured concrete wall.
Then it's unistrut and 12 LG Neon's on top.
It pivots with 1 hand...
I'm debating a coat of sealer before the panels go up.
 

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Pivots with 1 hand, minimal effort.
Such a gratifying feeling.
Huge thanks to the plethora of info here from all the great users and a sincere thank you to @Will Prowse and all the admins for making it happen.

For anyone just starting their solar journey, ground mounts are the way to go in my opinion. Just under a year ago the roofs were done.
Now I think I'm finally ready for winter...
 

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All I can say is I don't like wood for a structure that is supposed to last 20-30 years, is subject to decay, rot, cracking, flexes during heat and cold, dry and wet weathers. However, that being said, I think you should at least find a good penetrating wood preservative coating to give it a fighting chance and then keep applying it every few years as needed. Remember, panels don't shrink and expand, wood does, and it flexes under wind load.
 
glandpuck said:
All I can say is I don't like wood for a structure that is supposed to last 20-30 years, is subject to decay, rot, cracking, flexes during heat and cold, dry and wet weathers. However, that being said, I think you should at least find a good penetrating wood preservative coating to give it a fighting chance and then keep applying it every few years as needed. Remember, panels don't shrink and expand, wood does, and it flexes under wind load.
Click to expand...
Thanks for the advice, protecting and staining the wood is on my list of things to do after I take care of the deck that's seen 2 years of neglect.
The array has seen 60+mph winds with very minimal movements. I was monkeying all over it throwing up the rails and panels, it solid.
I understand the constraints of lumber and can assure you it's very sturdy.

It was meant to be a temporary mount while I prove out equipment and learn from my mistakes while I save money and plan my next system... My goal (that I will accomplish in the next year) is to find land to build on. I'm hoping the next owner wants the S & W facing Tamarack roof arrays.
The arrays will be steel and built to last a lifetime, the deck will be composite... They don't make lumber like they used to....
 

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RV10flyer said:
I have 50kWpv on PT lumber. 18 mo. It’s handled 60mph. Staining it like your deck will help it last longer. I’ll let you know how it worked out in 20 years. It’s 1/3 the cost and no shipping.
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How often do you stain it? And what do you use? I use Thompson's water seal.

My PT wood ground mount has been in the ground for about 14 months. I stained all of the wood before I installed the rails and panels then.

I re-stained the wood (vertical posts and some horizontal support posts) I could reach last weekend. My concern is the wood supports under the panels, I can't really reach the top of those 4x4's. Well technically I can, but I only have about 2 inches between the top of the posts and the panels, so it would be very tedious, time consuming work.
 
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