Next project is perimeter fencing on the homestead. There is existing fencing around some of the homestead, but it is old and not in good repair. I have researched fencing for awhile. I shared some of that research on this site in the post Perimeter Fencing. From my research, I have decided to implement treated wood post fencing. I have decided we need Mesh field fencing that is “knotted” so the fence has a little give. Welded seams for shorter runs. We are looking at post approximately 7 feet apart to try to keep the fencing in the ground through significant snow drifts.

Fence Break force

I want this fence to last as long as possible and thus am looking for Class 3 galvanized fencing. Galvanizing means the steel of the fence is immersed in molten zinc alloy which is resistant to rust. Each class indicates how heavy the coat of the rust resistance zinc. Class 3 allegedly last 2.5 times longer than Class 1 zinc coating. BTW, one reason I have chosen field post (8 feet set 4 feet in the ground) is that a fence is a vehicle barrier. Not a tank, but a normal car trying to drive _through_ the fence is not going to get very far. The car is strong enough to push through some post, but as the car or truck goes forward more and more, the fence eventually stops the vehicle.

Right now I am moving from concept phase to initial design and trying to figure out a rough level cost of our fence, or what we call a “budgetary quote.” The issue is how many posts will we need, and how much fencing. First some theories, which I will express as requirements.

The perimeter fence will be installed on 5 acres.
The land is flat, and with no trees along the fence line.
The perimeter fence is to help keep pigs, dogs and sheep inside the perimeter.

After we accept these constraints of our field fence, then we look to some math to tell us how much fencing and how many fence post we need. For that, I call my friend whom I call (on the Internet) the Wizard. He is the guy who develops most of the math on this site. He is extremely smart. Also, he helps us with these tiny little projects. Here is what the Wizard says.

We could condense it into one formula, but it would be messy. So we use multiple formulae’s which is more of a process. Not a hard one though. First, decide on how maximum distance between field post. Online research suggests 8 – 10 feet apart is normal. We can look at the cost for 7’ spacing.  If you want 7′ spacing:

1. L is the length of the stretch of fence in feet.

2. S = L / 7 is the number of sections in that stretch of fence. You want it to be a whole number of course. Round to nearest. If you insist on LESS than 7′ between posts, round up.

3. P = S + 1 is the number of posts. (You need an end post, plus one for each section.)

4. D = L / S is the length of each section. If you rounded to get S, this will not be exactly 7′.

So to break this down, we can look at this per acre. For your example: An acre is 43,560 square feet. If your acre is square (length=width), it is 208.71 ft by 208.71 ft since 208.71 x 208.71 = 43,560. Thus to estimate how long an acre is, it is 208.71 x 4 = 834.84. Thus a rough estimate of how many posts I am looking for would be

L = 834.84
S = 120 (834.84 / 7 = 119.24 and round up)
P = 121 (120 + 1)
D = 6.957 (834.84 / 120)

Thus to fence one acre of land completely you apparently need 121 posts, and 835 lengths of field fencing. Fencing is often sold in 330’ lengths, and we will use this in our initial design. Thus we need three 330 x 3 = 990 feet of fence. When I check the Red Brand pocket fence guide, it is right on the money. It says you will need three 330 feet rolls of fence.  , Please note a better way to do this is to measure the run with an outdoor fencing tape measure or a 100-foot tape measure.

Thus the Wizard continues “…you most likely want to build your fence it at 7′ until you are within approximately 100′ of the other end. Then measure what is left (easy to do with a 100′ tape, pretty easy with a 50′ tape) and apply the above. Then go down the tape and mark the post positions for the remainder, rather than measuring from one post to the next (which would be how you started).”

I did a little market research and visited three separate stores selling fencing products. Two companies the Idaho Fence Company and the Tractor Store sell fence post in “5 inches or 6 inches” which is written 5/6’. I wonder how many of the larger fence post you get. The North 40 store sells specific sizes.

However due to the sell ongoing right now at the Idaho Fence company that apparently have the better price by 1 dollar per post (which adds up, when you are buying a lot. 121 5” post will cost me $11.0 a piece from the Idaho Fence Company or $11 * 121 = $1,331 in post. I will need three rolls of fencing, and I will be getting that from the Tractor Supply as it is the only local company I can find that sells Red Brand fencing. That is $150 * 3 = $450. Thus a rough estimate for the products for fencing one acre is 1331 + 450 = 1,781. We will have to take this up to 5 acres to get a rough estimate of the entire 5 acres.