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PT Lumber suggestions

Started by xlogger, March 13, 2019, 05:34:06 AM

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xlogger

Getting ready soon to start up with my new pole shed for storing my live edge slabs in. 30x90. I got 6x6 pt poles from a local lumber outlet and know they are not as good as the older ones for putting in ground. Lots of suggestions I've seen. Some say not to tar bottom 3 ft of 6x6's and some say do. Also not to coat the bottom of the pole. Some say diesel and burnt motor oil. Looking for suggestions. My ground is clay/rocky soil.
I'm 65 now and want this shed up for another 30 years so I can be stacking lumber in it :D.
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

Don P

The real problem is what they are stocking, they do still make ground contact treated but the lumberyards aren't typically stocking it. They can get it. If you look at the tag what you want is UC4, use category 4, which is ground contact (UC4a) or foundation grade treated(UC4b). They tend to stock above ground rated treated, I've seen interior dry use treated stocked in one of the big boxes here, worthless. Don't expect the employees to know what they have, I'll quit there ::). Ground contact is more expensive but that will provide better protection and arguably might be cheaper than a homebrew solution that isn't going to penetrate even as deep as what they have already slopped on there. It doesn't much matter what you do a foot or more underground, rot happens right around ground level.

When we went from the old CCA to the modern non arsenic stuff there are so many formulations that calling out .60 for ground contact doesn't mean anything anymore so they went to this system around the turn of the century. On the tag look for "AWPA U1, one of the numbers below"

UC1- interior dry
UC2- interior damp
UC3- Exterior above ground
UC4a- Ground Contact
UC4b- Foundation Grade
UC5- Marine, a-Northern waters, b-Central, c-Southern

xlogger

Don, they didn't have ground rated near me and the closes place I could find them was pretty high and 6 feet longer than I needed. I talked to a couple guys that say they coated tar on theirs to above ground level. I hope if it doesn't rain here today to pour concrete in bottom of holes and start putting poles in the ground tomorrow. Still trying to figure out should I tar then or use motor oil and diesel mix or nothing. 
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

Don P

Tar thinned with diesel is basically creosote but your depth of penetration isn't going to be any better than what is there, kind of a roll of the dice.
We're in the same boat with the weather, laying block, we buttoned up last night but it didn't move in overnight.

moodnacreek

How about bore a steep angled hole, just above to just below grade [in the post] and pour in preservative and plug. Always more work.

Don P

I have bored and inserted borate rods into timbers then plugged the holes in post bottoms before. The theory is that if the moisture content rises the rods dissolve and saturate the >fiber saturation point wood. Phone companies have a borate bandage and have also used the rods. I have mixed feelings there which I'm sure others are about to chime in on.

Jim_Rogers

To reduce costs and to prepare for future repairs to underground rotted timbers you could use the short pole system.
In this system you put PT only in the ground, and above use regular wood.
You sister two or more pieces of PT at the joint.
Like this:


 

Years from now when the wood in the ground has rotted away, you jack up or hold up the barn and dig out the rotted piece and replace that section.
This greatly reduces the cost of buying long lengths of PT that will be above the ground level.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

florida

General contractor and carpenter for 50 years.
Retired now!

John Mc

Does no one use a sonotube with a bigfoot on the bottom and just pour concrete finished with a fitting on top to hold the 6x6 in place? No wood in the ground. I've seen a couple of buildings around here done that way that seem to have held up well.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

thecfarm

@Don P,thanks for the grades of PT. I had no idea. I booked marked this thread so I can find it again.
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Magicman

I made a screen shot of it so it is now in my photos.  ;D
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Don P

That stuff is also in Florida's link and at the AWPA website, I blow up computers too much to trust their memory :D

On the sonotube and short post ideas there is one thing to think about, lateral stability. When the wind blows a typical post frame is using the soil to pick up some bracing, that can be really sketchy on DIY stuff but it is something. When you pin to something at grade you've created a hinge, that is ok if you pick up your bracing elsewhere. For simple open structures like this I prefer to sheath my knee brace Y's across the posts to rigidly lock the braces to the frame.

John Mc

Quote from: Don P on March 20, 2019, 07:46:50 AM
That stuff is also in Florida's link and at the AWPA website, I blow up computers too much to trust their memory :D

On the sonotube and short post ideas there is one thing to think about, lateral stability. When the wind blows a typical post frame is using the soil to pick up some bracing, that can be really sketchy on DIY stuff but it is something. When you pin to something at grade you've created a hinge, that is ok if you pick up your bracing elsewhere. For simple open structures like this I prefer to sheath my knee brace Y's across the posts to rigidly lock the braces to the frame.
We added long diagonal braces on our garage/barn. We were told that with the height (Gambrel roof creates a very usable second story), it would get a little "whippy" without the bracing, whether the posts were in the ground or attached to the top of the concrete in the sonotubes. Siding is shiplap over the poles, girts and diagonal bracing; the endwalls are diagonally braced, then plywood over that, then shiplap.

It has had no problems for the 17 years it has stood. We do get some high winds that have torn roofs off of buildings in our area, but we are not in tornado or hurricane alley here, and we are very sheltered on two sides, more open to the south. Our long dimension runs east/west, so that south wall does get some fair wind loading.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

Corley5

A Google search for perma column brings up different systems and brackets for attaching wood posts to concrete.
Burnt Gunpowder is the Smell Of Freedom

Corley5

Sturdi wall is another product.
Burnt Gunpowder is the Smell Of Freedom

Ruffgear

Another vote for .6 pressure treated, code on all pole barns around my area. Box stores usually have to order it in, but (real)lumber yards usually have on hand

florida

We've done the Sonotube and Simpson bracket many times but it's time comsuming and expensive. I think the last 8" X 8" galvanized bracket I bought was over $125.00. Add the bolts, Sonotube, concrete and time and it will cost you more than a .6 PT post. 
General contractor and carpenter for 50 years.
Retired now!

John Mc

Quote from: florida on March 20, 2019, 02:39:46 PM
We've done the Sonotube and Simpson bracket many times but it's time comsuming and expensive. I think the last 8" X 8" galvanized bracket I bought was over $125.00. Add the bolts, Sonotube, concrete and time and it will cost you more than a .6 PT post.
Yes, it will certainly cost more. However, in our poorly-drained clay soils, PT lumber does not last very long, even if rated for "ground contact" or "in-ground" use.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

florida

John,
Many of our posts are standing in water half the year and in wet soil the other half. We do use the Sonotube  idea where we are attaching new structure to a standing building as the existing structure provides good lateral stability.  On those where that isn't an option we use UC5 posts which we also call "dock piles." Eventually even those will rot right at the water line but that is usually 40 or 50 years in the future.  If you are building a closed structure probably a standard foundation and framed walls will end up as less hassle and the same, or lower,  cost.
General contractor and carpenter for 50 years.
Retired now!

chet

This is a structure I put up this last fall. The posts are 6x6s built up from full size 2x6s. I had the treated 2x lumber (.60 CCA ) done quite a few years ago. One of the nice things of doing it this way, is the posts are able to be made to any needed length.





I have a couple structures built this way that are over 35 years old, with no signs of twisting or racking.
I am a true TREE HUGGER, if I didnt I would fall out!  chet the RETIRED arborist

John Mc

Quote from: chet on March 21, 2019, 10:37:09 PM
This is a structure I put up this last fall. The posts are 6x6s built up from full size 2x6s. I had the treated 2x lumber (.60 CCA ) done quite a few years ago. One of the nice things of doing it this way, is the posts are able to be made to any needed length.





I have a couple structures built this way that are over 35 years old, with no signs of twisting or racking.
What did you do at/in the ground? I can't quite see it in your picture.
Building up from 2x6s is supposed to be stronger than using a 6x6 (other than perhaps at the joints)
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

Don P

better qualify that. In the strength direction of the nail laminated plies the wood is stronger because of the distribution of defects, repetitive member increase and dimensional vs heavy timber strength. The nailing, splices and splice length factor into the actual post strength of a spliced post vs an unspliced post. But, nail lam was developed for sheathed buildings. When you use it for a post in an open building now the flatways plies are bending out of plane. That is substantially weaker. So they suggest well nailed cover boards over the ply edges to put wood in bending across its strong axis when the posts are used in an open building or for internal posts. The nailing pattern is tight in all of this. Google David Bohnoff, nail laminated posts, for more than you ever wanted to know. He has been making and breaking these posts for about 30 years.

John Mc

If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

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