Laminating 2x6s for pole buildings

[ray66v]

I bought laminated poles that were fully dried before they were made.

The lower sections are .60 retention treated, the upper parts are untreated yellow pine, with finger joints between the two.

When the glue is dry, they lightly saw them, to true them up.

The result is a near perfectly straight pole, with no shrinkage, warping, or twisting.

On a 30 x40 with a loft, they cost me about $200 more than ordinary poles. To me, were worth every penny. Especially, it you plan to drywall the inside, (as this eliminates a common point for big cracks).

 

[dave1949]

Which of these laminations are stronger -
Two 2X6's with 3/4" plywood sandwiched between
or
Three 2X6's

It's not a trick question, I have no idea myself.
Dave.

 

[rus_geek]

Which of these laminations are stronger -
Two 2X6's with 3/4" plywood sandwiched between
or
Three 2X6's

It's not a trick question, I have no idea myself.
Dave.

I think that will depend on the loading. 3/4" has little to no resistance perpendicular to it's surface, but then again, neither does a 2x6. One loading pattern is supporting the weight of the roof, snow, and anything stored in the ceiling. Another loading is wind loads from the side walls. If the building has walls, I wouldn't worry about racking loads, since the side panels will take up a lot of that stress.

One of these designs may fair better in only one of these scenarios.

 

[radioman]

They laminate 3 2" by 6" using nails every 4" with no glue.

Umm - it was my personal belief that anything that anything that is laminated uses glue for full surface contact. Putting nails or screws in something with no glue doesnt count as lamination in my eyes.

 

[EddieWalker]

Which of these laminations are stronger -
Two 2X6's with 3/4" plywood sandwiched between
or
Three 2X6's

It's not a trick question, I have no idea myself.
Dave.

I'm not an engineer, so this is just a guess based on what I do know and as a contractor.

For a post, the thee 2x6's would be stronger. They have more mass and will be able to support a greater load.

For a beam, the plywood will make the 2x6's much stronger and able to span a greater distance with less deflection that the lumber without the plywood.

Adding plywood to a post will not accomplish anything.

Eddie

 

[dave1949]

I'm not an engineer, so this is just a guess based on what I do know and as a contractor.

For a post, the thee 2x6's would be stronger. They have more mass and will be able to support a greater load.

For a beam, the plywood will make the 2x6's much stronger and able to span a greater distance with less deflection that the lumber without the plywood.

Adding plywood to a post will not accomplish anything.

Eddie

That sounds logical to me Eddie. I would guess the plywood lamination would out perform the other when the force is applied against the side/edge of the plywood layer. I have made some of these for beams and have always thought they are pretty darn strong. Never tried it for posts.

I agree with radioman, without glue, you are giving up a lot of the inherent strength of a lamination. The glue should take away the ability of the built up beam or post elements to flex or deflect without actually ripping wood fibers out of the adjacent layers.
Dave.

 

[SuperCobra]

I don't know what research has gone into this, but I have my doubts about using 2x6's instead of 6x6's.

First, I've found that the larger the PT wood, the straighter it tends to be. PT 2x6's are hit or miss on whether they will stay straight, or twist on you. When I buy them, I buy extras because I know a few of them will do something on me. Even after picking through the pile and getting the straight ones, some will still do what they are going to do.

Second, I think that the solid piece of 6x6 tha is notched is much stronger then three 2x6's. I don't know how true this is, and it could easily by to a degree that both are plenty strong enough with an insignificant difference. If you need to support ten thousand pounds, and one will hold 20 thousand and the other will hold 25,000 pounds, then it doesn't make any difference.

Third, I know that posts are treated to a higher degree, or percentage, to be set in the ground. Off the top of my head, there are three basic ratings for pressure treated wood. Outdoor use, like decking is the lowest rating. The next is dirt contact, such as a post set in the ground. The highest rating and treatment is for posts in water. I've never seen a PT 2x6 that was rated for ground contact. On the labels, it will say what percentage of treatment the wood has. Look at the 6x6 and compare it to the 2x6.

I realize that it's becoming fairly common for barn building companies to use 2x6's for thier posts. I would like to hope that they are using them with the rating for dirt contact, but I don't know this for sure. I think the big advantage to using 2x6's is that it's faster to notch the posts. In fact, you don't notch them at all, you just cut the board to length and then attach it again with the space for the notch. When time is money, that's what you get most of the time.

Eddie

Thanks Eddie,
That was pretty much what I was getting at. I haven't seen "ground contact" 2x6s readliy available at a local home improvement store. I was looking for something readily available and convenient. 2x6s would have more length options, easier to transport, lighter to place in holes, etc. However, if the ACQ is so corrosive I need SS fasteners and even then it isn't ground rated, it is not worth the extra effort. However, however, I've seen the plastic sleeves you can put the posts in - that would be an option if I could find them locally - same with permacolumns.

 

[/pine]

[FWIW]
I once had an engineer design a post and beam to replace a bearing wall and he insisted that I support the beam with 4x4 posts rather than multiple 2x4's

 

[radman1]

I would go with laminated 2x6's for the posts. Morton, Cleary, Menards, Astro and about any other newer pole barn shed now uses laminated 2x6's. They are stronger. The added strength is for the wind loads and not necessarily for the vertical loads. I would just go to Menards (or lumber store) and order the laminated posts and not mess with making my own. Then they will be made correctly. They can get about any length you desire. 6x6 square posts may twist, the laminated may have minimal twist but are much straighter and more true overall. I added a lean-too on an existing 60x100x16 pole barn shed this year. The lean-too was 26' in depth. I wanted a front clearance of 13' and pole spacing of 25' for farm equipment. The company/engineers that supply the material for Menards designed the whole thing for the snow loads in my area. The front posts were 4, laminated 2x6s, with 3 laminated, 16" wide engineered lumber beams, 25' long for the headers and 2, laminated 14" engineered beams for the 26' joists which were spaced every 10'. 2x6 purlins every 2 feet between the headers.

 

[QRTRHRS]

Here is a good idea, maybe.

3 Ply 6" Laminated Column | PERMACOLUMN

I forget exactly but these are rated for wind loading at least the same as any post.