In order for your fence to stand strong throughout the years without needing a timely replacement, you need the right kind of fence posts. But even though fences may weigh a lot, fence posts can hold a lot more on them than you may think they can.
A fence with 4×4 fence posts standing vertically and properly anchored in the ground can hold a weight-bearing load of approximately 10,000 pounds. Likewise, a 6×6 fence post can hold about 24,000 pounds. Steel posts can withstand 360,000 pounds of force; with vinyl withstanding 165,000 pounds.
Each kind of fence post has its own purpose, and the kind of fence post you need will be determined by a number of factors. In this article, we will explore which fence posts hold more weight, and which will be a better choice for your next fence.
The Weight A Fence Post Can Hold
The weight a single fence post can hold is dependent on the material and size of the post. To make things simple for you, we made this table.
The Shear Weight Capacity is the amount of force the material can take before it permanently changes shape. It is also known as Tensile Yield Strength, and is measured in pounds per square inch.
| Shear Weight Capacity (PSI, Pounds Per Square Inch) | Size of Post (in x in) | Total Weight Capacity For One Post (Lbs) | |
| Cedar Wood | 850 | 4×4 | 9,682 |
| Cedar Wood | 850 | 6×6 | 23,876 |
| Steel | 40,000 | 3×3 | 360,000 |
| Vinyl | 6,600 | 5×5 | 165,000 |
Do You Need 4×4 Or 6×6 Posts?
When building a fence with wooden posts, you have a couple sizes of posts to choose from: 4×4 and 6×6 posts. The numbers 4×4 and 6×6 refer to the width and depth of the post, but are always slightly off, so a 4×4 post will be approximately 3.375 inches wide by 3.375 inches deep. A 6×6 will measure around 5.3 inches by 5.3 inches.
The great majority of wooden fences are made with 4×4 posts, as a wooden 4×4 will be more than sturdy enough to hold most fences. 4×4 posts are also quite a bit cheaper than 6×6 posts, so if you are building a fence surrounding a lot of area, 4×4 posts will be a significantly more economical option.
However, though a 4×4 will fit most use cases, there are some instances in which I may use a 6×6 post:
- If the region where the fence is experiences regular strong winds, and I want a wooden fence.
- If the fence I am building is taller than 6 or 7 feet from ground level.
- As the posts for a gate, especially if the gate is solid metal or heavy wood.
- If I am building a fence designed to keep people out rather than simply for privacy.
This list is not completely comprehensive. Sometimes, people just want to make absolutely sure that their fence lasts just about forever, and will use 6×6 posts rather than 4×4 posts.
If you want to do this too, just be aware that 6×6 fence posts cost significantly more than 4×4 posts.
Just remember that unless you are doing something out of the ordinary, a 4×4 post will be plenty for the fence you are building. If you are still concerned about weight and sag, spacing the posts closer together can do wonders.
Additionally, consider steel posts for their superior weight capacity and durability.
Does Post Depth Impact The Weight Capacity Of A Fence Post?
The deeper a post is anchored into the ground, the sturdier and more stable the post will be. That is pretty much a universal truth that we know thanks to Archimedes and the laws of physics.
Luckily, it doesn’t take a degree in physics or knowledge of advanced calculus to know how far your posts should be anchored.
Just like when we discussed 4×4 and 6×6 posts, for the majority of fences, burying your post in the ground at a depth of 1/3 to 1/2 of the height of the fence above ground will be just fine.
With a 6 foot tall fence, then, you would bury your posts around 3 feet into the ground, and need 9-foot tall posts. Keep in mind, the deeper the post is, the shorter it will be above ground; requiring you to purchase longer posts.
However, this also can change depending on the climate of where you live or want to put a fence.
Even though the depth of the post will help your fence be sturdier, there are other factors at play that affect what depth you should have your posts, including how wet the soil is, where the frost line is in your soil, and more.
There will be occasions in which you will have to bury your posts deeper due to these different conditions.
When in doubt, be sure to check the fence construction code for your area before building your fence. This alone could save you from having to buy a new fence in a couple of years because of your fence posts rotting and splitting.
Wooden Fence Posts VS Steel Fence Posts
Steel fence posts are great options if you need posts that can hold more weight.
More and more these days, you will see fences be made using steel posts. This is especially true in subdivisions and neighborhoods, due to the cost efficiency and durability of metal posts.
Steel posts work great when you are wanting to build cheaply and effectively. They hold a lot of weight, even though they are hollow, and are essentially waterproof.
The steel posts can effectively last forever, as they don’t rot and hold up very well to the constant mutilation caused on wooden posts by string trimmers; the only thing you’d need to replace is the wooden boards.
That being said, building a fence with steel posts may not be right for everyone.
Steel posts are not necessarily the most aesthetically pleasing and are definitely difficult to modify if you needed to. Many people prefer the modularity and looks of wooden posts to steel.
However, steel posts great for high wind areas. During high winds, the sheer load on the fence is quite high. They have a much higher sheer force tolerance and will last much longer than wooden fence posts, especially if the force of the winds is high enough and regular.
While wooden posts may allow for a much sturdier fence, as you can easily reinforce your fence, they are a better option if you don’t live in an area with strong winds.
If you do live in an area with high winds and aren’t concerned with the aesthetics of steel posts, they will definitely last much longer than wooden posts and will be cheaper.