What is the best fence post depth? That depends (of course) on what type of fence you are building and which post you are putting in the ground. We’ll cover a few here with some general fence builder rules.

Privacy Fence Post Depth — 1/3 of Height

The general rule of thumb for privacy fence posts is to bury them 1/3 the depth of the height of the post. This is easy for your typical privacy fence. Use 8? posts, bury 2? in the ground, and you’re left with a 6? post on which to build a fence.

Concrete is still a good idea (I recommend it), especially if you live in an area with high winds or occasional hurricanes. I’ve even drilled a 9/16? x 8? hole in the bottoms of the posts and driven a piece of re-bar in with about 12? sticking out. The result is a post buried 2 feet in the ground, with re-bar another 12? (driven into the clay soil), surrounded by concrete — very strong posts. Overkill? Whatever, dude.

Farm & Ranch Fence

Your typical farm or ranch fence, especially one with wire stretched, has 2 types of posts — line posts and corner posts.

Use the 1/3 of height rule for the line posts depths. With 6 foot posts, you will probably bury 1.5 to 2 feet and end up with a 4 to 4.5 foot post. For corner posts, you might want to use a rule of 1/2 the height for the fence post depth. So, a 5 foot tall corner post would probably be buried 2.5 feet in the ground — probably more like 3 feet buried of an 8? post.

These "Green Treated" poles have a light green color because they are treated with CCA

Green = CCA

9 times out of 10 green treated wood simply means CCA treated wood. CCA, of course, is Chromated Copper Arsenate, the stuff that was banned for use in most residential applications such as decks, railing, fences, and the like.

People freaked out about the “arsenate” component of the wood. Arsenate is a naturally-occurring form of arsenic so people got freaked out but the stuff is all around us anyway. Stick your hand in any patch of dirt in your backyard and you’ll probably be touching more arsenate than if you were to do a handstand on your CCA treated deck (which you can’t make anymore). I’ve researched it a decent amount and have seriously never seen any evidence that it actually causes any health issues. Oh, yeah. I digress…

CCA is still allowed for use in water and for many commercial and industrial applications because it is an ultra-effective treatment to dramatically increase the life of wood. Wood treated with CCA gets a green color that might range anywhere from light young-lemony-green with light treatment to near-forest green with a saltwater treatment (2.5pcf).

It’s that simple, really. Green treated wood is wood pressure treated with CCA.

Other Treatments

To separate themselves from the green treated wood, ACQ treated lumber producers branded their ACQ treated wood lumber as Yellawood, which you’ve probably seen on everything from store shelves to billboards. MCQ is basically clear, or colorless. In fact, the very strength of being clear is kind of its weakness, too, because when MCQ lumber is delivered many people do not believe they have received treated wood. It really is that hard to tell sometimes.

CCA is a better product anyway. I think we should drop the Yella stuff and the clear stuff and the whatever stuff and go back to the good ol’ green treated wood that works so well. It makes me want to only build on water where I know I can use the good stuff.

Of course, there’s also BLUE treated wood which is usually a borate-based treated wood but that’s a different conversation.