Construction of Laminated posts for Pole Barn

[MarkV]

Steve, you’re an engineer so I bow to your expertise as far as wind load. We tend to build with plywood or T-111 siding rather than metal and as you know that adds considerable shear strength. Do you agree that a laminated post will offer more strength than a solid 6x6? How do you feel about the construction detail of the pole itself? Wind load is not a big factor in the local codes where I work so I may be wrong making blanket statements. I do believe what I have said meets the codes of our area.

Richard, Wish we had ready made laminates poles around our area. I have never seen them. Are the ones you get pressure treated on the lower half only? That sounds like the best of both worlds to me.

MarkV

 

[SteveBenson]

>We tend to build with plywood or T-111 siding rather than metal and as you know that adds considerable shear strength.

Absolutely. Metal siding provides negligible shear bracing. Conventional bracing or strap bracing is needed when using metal siding.

Proper bracing no matter how it is achieved will reduce the bending load at the base of the pole (where it would be highest if not properly braced) due to wind load, which is a good thing. However, when you get into some of the taller buildings (18'+) windloads can genereate large bending loads near the vertical center line of the side walls. This probably isn't much of a factor in your 10 an 12 foot high buildings (using 6x6s), just your taller buildings as the bending load increases both due to increased load area and longer beam length as the side walls get taller.


>Do you agree that a laminated post will offer more strength than a solid 6x6?
Absolutely. Since only one material is being used in the laminate the better strength characteristics comes only from the minimization of impact of defects. Defects will be limited to each ply AND sterengthened by attachment to adjacent plys.

>How do you feel about the construction detail of the pole itself?
I would buy them from a glu-lam manufacturer. Nobody can do it better than them. They are PT on the bottom only and use finger joints at the end joints. I'll see if I can find the link to the manufacturer I saw in PA. All the PT & SYP comes from down your way, there should be something in your area.

 

[SteveBenson]

This is the manufacture (RigidPly Rafters) is saw them from, but from a different lumber yard.

Glu-Lam Posts

 

[yooperdave]

What some people here seem to be missing is that the perimeter poles are subject to both axial loads due to gravity loading, and bending moments due to wind loads and sometimes eccentric loading from the truss connection.

This is why continuity is so important in the poles. Making a built up column with splices a foot or two apart is asking for trouble. Glue laminated columns as stated earlier are the best, but are also very expensive.

Why don't you mechanically laminate full height members together? This would seem to be an acceptable alternate.

If you are trying to acheive the section modulus and moment of inertia of a solid 6x6, why don't you use (4) 2x6's and use that price to compare to the cost of the 6x6?

Just some suggestions.

Yooper Dave

 

[cowboydoc]

Mark,

You can buy them either way. You can get pressure treated all the way up or just pressure treated at the base.

 

[gmason]

Sorta just for fun, but also to see how much $$ and work it would take to build a laminated pole for my pole barn project, I bought 3 (2"x4"x 8') and 3 (4"x4" x8'). They we on sale at the local HD. Also I bought a tube of Liquid nails and a box of 3" 12d gal ring nails.

I cut one of the 2x4's in half and glued this, starting at one end of the 4x4, and nailed every 18" and 2 and each end. I used me biscut joiner and put #00 biscuts in the ends of the 2x4's and glued and nailed the next full 2x4 to the 4x4. So I basically stagered the joints by 4' with glue, nails, and biscuts holding it all together.

So now I've got something that is a true 3.5" x 5" x24' and if I attach a 2x6 to the adjoining side, then I'll have a 5"x5" (after I plane off the extra edge of te 2x6).

I've already got 6 30' power poles that are a good 12" dia for most of the structure.

Does anyone know of a comparison eng rating chart for comparing load ratings for hardwood beams vs steel I beams, or LVL's, or the wooden I beams ?

thanks
gary

 

[SteveBenson]

>Glue laminated columns as stated earlier are the best, but are also very expensive.

I've never priced the poles myself but I have heard the glu-lam poles are reasonable if you are shopping for longer poles (>16'). I'm sure there is some length were the glu-lam posts become a no-brainer. Probably not for your 12', 14', or 16', posts though.

I used 16' solid posts on my last barn and ordered 6 extra "just in case". Boy was I glad I did that, a bunch were warped and or twisted, and couple had some big nasty cracks down the length of the pole. In the future it's nothing but glu-lams for me. I'll probably save money as I know I won't have to buy extra /forums/images/graemlins/grin.gif

 

[Anonymous Poster]

Take a look at this site. I'm not sure it has a comparison chart but it has all the info you need to compare them yourself.

Engineering Fundamentals

 

[kubotasaurus]

RE:>I would buy them from a glu-lam manufacturer<

I'd agree with you there. Back in my engineering days it was common to see failure of bonded joints that were created in the field. You CAN do a good job of it, but you need to pay very close attention to the adhesive you're using, the conditions you are using it under (temperature, humidity) and maybe most important, how well you can get the surfaces to mate while the bond is curing. The glu-lam guys do all this in big presses and know their adhesive qualities. It pays to watch the details. There's not many things uglier than a long delaminating beam or column only held together by nails.

 

[Darren]

Marine grade PT is 2.4 as compared to the .4 deck material at the big box stores. Big difference. The stuff is heavy. Don't know what .8 is but anyone who builds docks or bulkheads in salt water wouldn't touch .4 or .8 stuff.

FWIW, I had no problem getting a quote on true 8x8 sized marine spec. 26' posts.

 

[yooperdave]

Don't know what .8 is but anyone who builds docks or bulkheads in salt water wouldn't touch .4 or .8 stuff.



They are referring to the density of the preservative treatment being retained in the wood.

Green treated has the least, brown treated has more, and marine grade has even more yet. This is why the wood is so heavy.

Yooper Dave

 

[Anonymous Poster]

buckeye:

Are you dead set on the "pole barn" style? If not consider quonset. I have designed and built a couple smaller structures using laminated frames. Advantages include less material per sq ft of floor, stronger load factor (for same material) and cheaper (for same quality).

Of course, like a carpenter with a hammer in their hand (the old cliche), I have built sailboat - ply over frame - so everything looks like a sailboat. Very strong. Laminate frames using resorcinal glue (or liquid epoxy - I guess the West system is still around), notch for longitudinal stringers, and, if you really want it strong, build up your own plywood using cheap door skins (one layer in one direction 45 degrees, then the next layer in the other direction). No hardware needed (except staples to hold the ply together until set up). Or, use thinner CDX ply running fore-aft. The slight bend on the ply greatly increases rigidity. The resulting structure will be extremely light weight and very, very rigid and strong. It can be built up/bolted to a concrete footing.

Another option, if you don't want to build it yourself, is to purchase corregated metal arches (bolted together) which are tipped up one at a time. The corregation in the metal provides great rigidity. Quick, easy and relatively painless.

JEH

PS How do you like your TC40? Just bought one a few months ago (only 100 hrs so far) myself and it works nice for me. Have you have many probs with it?

 

[buckeye]

grimreaper:

Thanks for your comments. I am not really set on any one type as of yet, but I am leaning towards the pole barn. No matter what it will be, it will be something I put together myself along with my Dad and some friends.

As for the TC-40, it has been great for us. I would buy it again, no questions asked. The only problem I have encountered to this point is with my 16-LA loader. I just wasn't attaching and detaching it correctly and slightly bent the metal that allows the support leg to pivot on. Thanks to Jinman, I have downloaded a series of pictures that shows a better way to do things and I should not have any more problems. Just to be sure, Dad and I are going to weld a support behind the metal this fall when it gets cool and we have time for shop work.

 

[Gatorboy]

I am probably repeating what is already said, but what I have found to be the benefits of laminated posts are:

1. Lower cost -- no need to have PT all the way up, just the portion that is in the ground.

2. Better treated wood -- 2x6's are going to be treated more uniformly than a 6x6 would. Not sure how much of the treatment of a 6x6 would make it to the middle of the beam.

3. Weight - Untreated wood for the upper portion of the pole will be far lighter.

4. Ease of use - Setting your posts in the ground should be far easier with a shorter lower section of laminated PT than trying to set a 12'-16' PT post.

Morton Buildings use the build-up method for making posts. I am sure if there were problems with using them, they would have stopped years ago.

I started making some posts for building my own Pole Barn -- I made them with one 2x6x8 and one 2x6x12. The 8' piece is in the middle, and I cut the 12' piece into a 6'8" piece and a 5'4" piece.

 

[Darren]

What I meant was I didn't know for what application the .8 treatment was intended. If you order the material from the treatment plant you can also specify the grade of lumber. Because of the process, vacuum first to extract moisture then pressure to force the CCA into the wood over a period of time, there should be no problem with treating the "stick" all the way through at least for the marine grade stuff. The stuff comes out with a dark green almost black coloring.

FWIW, if you're going to use a glue consider resorcinal. It's a structural glue meaning that if you try to break a resorcinal glued joint the wood fibers will tear before the glue will release. Resorcinal is also insect proof and waterproof. Not water resistant, waterproof. It may be the two part glue others have mentioned.

For the amount of labor involved in gluing stuff up, I'd find a local lumber yard that buys their treated lumber straight from the treatment plant and order the marine grade. A Home Depot or Lowes will not be able to do that. Another plus is that carpenter bees won't bore holes in your posts if they're treated from top to bottom and the structure will still be standing long after something built with lesser treatment has rotted.

The .4 stuff buried in the ground is eventually going to rot. The heavier the treatment the longer the life. Do you want your structure supported by .4 or .8 treated posts or 2.4?

 

[SteveBenson]

>The .4 stuff buried in the ground is eventually going to rot. The heavier the treatment the longer the life. Do you want your structure supported by .4 or .8 treated posts or 2.4?

You are right about marine grade, I was wrong. .8 is not marine grade. Someone told me that once and it stuck I guess. I did a little research:

Termite protection: .25 pcf
Ground or fresh water contact: .4 - .8 pcf
Saltwater contact: 2.5 pcf

 

[Anonymous Poster]

<font color="blue"> Termite protection: .25 pcf
Ground or fresh water contact: .4 - .8 pcf
Saltwater contact: 2.5 pcf
</font>

Wow! That is a great jump up to the salt water rating.

Anyone know the reason for this? Not sure why, but I would have expected less problem with salt water vs fresh water, rather than greater rot potential.

 

[Anonymous Poster]

From what I've heard there's a few reasons for the jump.

1. Salt water is heavier than fresh and therefore seeps into the grain easier it takes more density to keep it out.

2. Some of the critters that grow in salt water attack the wood more voraciously.

3. The chemical makeup of salt water is such that it will corrode or rot almost anything.

I'm sure there are others who know more than I about this.

 

[knucklehead]

Jim - I haven't been around the PC for a couple days. Looks like you got enough answers, huh? I searched Google on "built up posts", then "laminated beams", then "laminated posts", and in amongst the thousands of hits, I found a manufacturer's page that gave a few specs. There are a lot of engineering sites, as you may imagine, but I was trying for a cookbook solution that could be used to go right into building design/construction without reading extensive research and digging out the old books. In my opinion, you'll find pretty much what you need right here!

Back in '01, Chuck52 started the Pole barn thread. It's got pictures by Bill_In_MI of the built up posts Morton uses, about halfway down the first page of posts. Following the pictures, there's more talk about built up posts that you might find interesting.

 

[HuntsEndFarm]

<font color="blue"> This is why continuity is so important in the poles. Making a built up column with splices a foot or two apart is asking for trouble. Glue laminated columns as stated earlier are the best, but are also very expensive. </font>



<font color="black"> </font> I'm not sure I agree that the continuity is important provided that the building is braced adequately. I am currently in the middle of a pole barn project (I'll post pictures soon). I designed the construction according to an adjacent Bonanza horse barn (I think Morton bought them out). I am using 3-2x6 CCA to 1' min above grade with staggered heights. I will then extend these with 2x6 SPF forming a pocket at the top to drop my 2x12 rafter into. 2x6 T&G sheathing will be installed around the perimeter of the building, extending above the post joints. My Bonanza barn, with the same construction, has stood for 20 years with no problems. Now I will say that if I wasn't using the T&G sides (which add alot of stability) I would install diagonal metal bracing all the way across each and every wall.

Keep in mind though, that if you have any freestanding exposed columns that these should be 6x6. For instance, some horse barns have an overhang where the horses can stand under. These outer posts will take a lot of side impact (esp. if you have an itchy horse) and no laminated pole would be adequate.

Advantages:
Knowing I would be doing this project by myself, I felt it easier to move and attach everything in smaller pieces. The posts are much less prone to warping and twisting and the tops provide a nice slot for the rafters without getting into tricky cuts.

Another great advantage....When the gravel truck backs over one of your posts, its an easy fix. Try fixing a cracked 6x6x16. /forums/images/graemlins/frown.gif