Construction of Laminated posts for Pole Barn

[buckeye]

Thanks for all the great input! I knew I would not be disappointed from your all's comments and advice.

I guess I am looking into the laminated posts instead of 6x6 due to what I have seen around lumber yards here. Basically to get a 16' or 18' 6x6 that is straight or true is difficult, and they are usually still wet at the yard. When they dry, I expect them to warp and twist causing problems.

Secondly, while at the Ohio Farm Science Review last year I noticed that several of the large building manufacturers were making laminated posts. I just casually noticed this at the time and did not look very closely at the construction. I'll definetely look at them this September at the Farm Science Review, but I hope to be underway with my project by then.

I like the idea of pressure treated posts for the first set and then using regular lumber for the upper sections. Talking to one of my buddies last night, he said this is what Morton is doing (or at least he has seen them do it).

Thanks for the comments and if you have any more, keep them coming!

 

[buckeye]

</font><font color="blue" class="small">( I did a little quick search and the only spec I could find was a maufacturer's recommendation that 6x6 posts be three continuous pieces of 2x6 glued, clamped, and nailed on 12" centers on both sides. Every comment I read gave the impression that gluing was crucial. )</font>

Knucklehead:

Where did you search to find this information. I did a quick Google search, but did not really find anything like what you are talking about.

Thanks for your comments. I found them very interesting and helpful.

 

[MarkV]

I sure don't have all of the answers but do have a couple of thoughts as this post progresses. I don't believe I would go with a laminated post just to save money. I agree that the non-pt wood is cheaper but I bet after you look at the cost of the bolts, nails and glue, if used, that pricing will not be much different. You also need to consider that it will take some time to build the post and factor that into the pricing equation.

I believe a little research would find that a laminated post is stronger than a solid 6x6 with or without glue in this application. It also doesn't make much difference because both are adequate for what we are talking. If your snow loads or dead loads are going to be greater than normal you need closer spacing of your posts, not stronger posts. The important factor is the distribution of the load to the ground or footing to minimize the point loads.

In my opinion side loads, wind load, glue and to some extent even the splice are a moot point in this situation. When you think about the skeleton of the normal pole building the posts transfer the weight of the structure to the ground. On top of the posts sets a beam on which the trusses will sit. The beam transfers the roof weight to the posts. The posts are not carrying side load and there fore the glue and heavy fasteners are of less importance in this application. Multiple 2x4's nailed together carry huge headers in a house. Wind load or shear does need to be considered but that is a function of the sheathing or diagonal bracing in a pole building. Your sheathing and or bracing turns the building into a ridged diaphragm that distributes the side loading over the whole structure not the individual post. It is like a stud wall before it is sheathed. There is very little lateral strength and you can shake the whole wall easily. Add some sheathing and you have created a diaphragm that distributes the load over the whole wall and it is very ridged. There is very little force being applied that would cause a post to delaminate.

The important thing to remember when we talk laminated posts is that we are not talking beams. A beam is for carrying side load and the engineering of size and fastening becomes much more important. It is a totally different application than we are discussing in this post.

Now I am not a structural engineer, just a guy that has been swinging a hammer for a lot of years to pay the bills. Hopefully one of our engineer members will chime in and verify or correct my thinking about laminated posts.

MarkV

 

[cowboydoc]

Adv: It's a lot cheaper, easier to work with, and stronger. Have you checked the quality of 6x6 of late? You don't get a knot all the way through, or a crippled up twisted mess.... And a lot of farmers are needing 18' or more sidewalls, hard to get 24' beams & pay for all that pressure treating...


Rambler you are exactly right!!! The last barn I built we needed 30' posts. Try and find a 30' treated 6x6 that long! They are also ALOT cheaper and the strength is greater than a 6x6.

 

[cowboydoc]

You also need to consider that it will take some time to build the post and factor that into the pricing equation

These posts are available everywhere at lumbar yards. Really no need to make them. They also come with a 50 year guaranty. Anything happens not only will they replace the post but they'll pay to have the new ones put in. At least this was the warranty on the last ones I got.

 

[Inspector507]

I saw a post on here recently that contained the name of a Pole Barn "erector/builder". I can't find that post now, but on the builders website, it gave the test results of 6x6PT vs laminated posts. The laminated post had less sway and more resistance to side loads.

 

[RobS]

A friend has a Morton building with laminated posts. Very well built. The laminating provides several benefits: Using PT for the lower sections has already been mentioned but it also makes attaching the header beams a lot easier. You can let the center lamination run to full height and cut the outers shorter by the width of your header. Now you've got a tenon to accept a 2X header on each side. A couple of bolts in each and you're all set for trusses.

Some pictures at Morton /forums/images/graemlins/smile.gif

 

[s1120]

One thing I don't see anyone saying is that a 2x6 can be PTed a lot better then a 6x6 post. The inside of a 6x6 will have very little treating, wile a made up post, will be treated better. The treating will soak into the center of a 2x6 more.

 

[SteveBenson]

>Keep in mind that with a pole there are no shear loads or side loads. All the weight is being carried straight down.

This statement is very untrue. Extremely large bending loads are placed on the poles due to wind loading. Some states require 120 mph wind loading, like FL. Depending on the orientation of the lamination, shear loads may be present in the lamination boundary due to the bending load.

 

[SteveBenson]

>These posts are available everywhere at lumbar yards. Really no need to make them.

Yes, I've seen Glu-lam posts advertised in Lancaster Farming. I will definitely use these on my next building. the ones I saw advertised came in any length, the base PT to .80 CCA (that's marine grade PT), and used finger joints to join the board ends. I know morton makes there own, but I would buy them. Those guys are pros at lamination and you get the warrentee.

All these points have been brought up, but I would agree with the following statements:

1) GL Posts are much stronger.
2) They are much more dimensionally stable.
3) Better PT at base (for the manufactured ones).
4) Cheaper for long lengths.
5) High quality (straight) long posts are possible.