Pressure treated wood ratings (pole barns)

[IHDiesel73L]

I started a thread below about concrete columns because all of the conflicting information about the potential for rot in pole barn posts was driving me toward concrete. However, I stumbled upon these links:

AWPA Technical Information for Homeowners

http://www.wwpinstitute.org/documents/RevisedSpecGuideJan2012_000.pdf

As it turns out there are far more grades of pressure treating that most people probably realize, from UC3A, suitable for above ground use in areas of rapid runoff and not exposed to prolonged wetting, to UC4C, suitable for ground/freshwater contact, exposure to all weather cycles, severe environments, decay, fungi, and insects. There are grades beyond that, meant for salt water pilings, etc... The point is, that I think more people need to look closely at the tag on the lumber and to ask more questions of the supplier. I'm going to call my local lumberyard tomorrow to see if they stock or can order UC4C lumber and what the cost is.

 

[mfreund]

Good information!!

 

[EddieWalker]

The treated 2x lumber is all rated for use above ground. Treated posts from 4x4 on up to the round posts are all ground rated. 4x4 posts are strong enough for a building, but the new treatment process causes a lot of them to twist real bad. 4x6's are a safer bet, but some of them will twist over time. I only use 6x6 posts for jobs I do for clients, and for my own stuff.

Eddie

 

[s219]

TSC sells some very nice 8 foot fence posts in 6-8" diameter, extended ground contact rated, and they are not veneer cores, so they are quite stable (on the flip side, they are not perfectly straight, but that is not usually an issue). I used these extensively when building stairs for my pier. They were a few bucks less than 6x6 timbers from the lumberyard. Best of all, the poles were dry and easy to handle. I find most 4x6 and 6x6 timbers from the lumberyard are still sopping wet from treatment, and weigh a ton.

We also had some marine grade timbers for the actual pier, which came from a marine construction supplier. They are rated for immersion. That was some real nice wood. I saved a bunch of scraps for miscellaneous use in damp locations.

Funny thing, I grew up (in CT) calling it all "pressure treated". Here in VA, all the locals call it "salt treated", even the building inspectors. They look at me funny whenever I called it pressure treated.

 

[IHDiesel73L]

The treated 2x lumber is all rated for use above ground. Treated posts from 4x4 on up to the round posts are all ground rated.

Right, but my point is that there are three different grades of ground contact rated lumber alone:

UC4A
UC4B
UC4C

Based on what I've read I wouldn't use anything rated less than UC4C-I would imagine that not all 4x4s, 4x6s, or 6x6s are rated the same.

 

[jel1988]

I've built a number of pressure treated foundation, we put a 1' wide strip of 3/4" foundation grade pressure treated plywood 1/2 below grade as a sacrificial barrier as the vast majority of decay occurs within couple of inches grade. The grade strips should be changed out every 25 to 50 years. Just an idea.

 

[IHDiesel73L]

Running some errands today I stopped into the local big box store and was curious-the following are pictures of the tags on a 4x4, 4x6, and 6x6 I found there:







Notice that all are rated "UC4A", the lowest rating for ground contact. In the AWPA document I posted above, UC4A is recommended for fence posts, deck posts, and utility poles in regions of low decay potential. The next highest rating, UC4B, lists "permanent wood foundations" and "building poles" in "regions of high potential for decay" as applications. Food for thought...

 

[Rustyiron]

What Eddie might be saying is that 2X material ie; 2x4 2x6 etc is no longer (that I have seen) to be found rated for ground contact. I much prefer to laminate my own posts from 3 or 4 2x6 (pt) for a stronger, straighter and much better "treated" than a post that is just about guaranteed not to twist up when drying. Unfortunately those days are gone. Your 3 examples are considered timbers and allowed the better treatment for GC.

 

[IHDiesel73L]

What Eddie might be saying is that 2X material ie; 2x4 2x6 etc is no longer (that I have seen) to be found rated for ground contact. I much prefer to laminate my own posts from 3 or 4 2x6 (pt) for a stronger, straighter and much better "treated" than a post that is just about guaranteed not to twist up when drying. Unfortunately those days are gone. Your 3 examples are considered timbers and allowed the better treatment for GC.

The fact that 2x lumber is not rated for ground contact is besides the point. The point of this thread is that all ground contact rated PT lumber is not created equal. I don't think a lot of people realize that-I definitely didn't until I bothered to research it. I'll be curious to see if I can source UC4C or UC4B rated lumber through a local supplier and if so, what the cost difference is from UC4A. UC4A is NOT recommended for permanent wood foundations by the AWPA, so I wouldn't use it for pole barn posts. There are plenty of folks who have had barns built with pressure treated posts that still rotted off. I wonder if it was because they used 4As instead of 4Cs?

 

[tcartwri]

The poles that utilities use are rated for 80 years I believe. You will not find those at any local supplier obviously, and there are pretty strict rules on how close they can be to your well etc... I had a link for a Canadian supplier, but I cannot find it. Not sure if they would even sell to a private individual.