Concrete For Fence Post Installation

Prepping For Concrete For Fence Post

Proper concrete for fence post installation is extremely important . Several time a week, we have customers who ask what is the best way to mix concrete.

Let’s assume that you’re going to be installing a 4″x4″ wood post for a wood privacy fence or a 5″x5″ vinyl post for a 6 foot vinyl privacy fence.

Here in Fort Collins, we recommend digging your post holes 9″ to 10″ in diameter with a post hole digger or a 2-man auger using 9″ or 10″ auger bit. If you have more than 20 holes to dig, we highly recommend a 2-man auger. These can be rented from your local rental yard and rental rates are approximately $45 per half day and $85 for a full day. The depth of the hole for concrete for fence post varies in what part of the country you live in. Here in Colorado our average depth is 24″ to 30″ deep. The average amount of concrete for fence post is approximately one to one and half bags of 60 lb. ready mix concrete. Retail for a bag of ready mix that we sell here at Cedar Supply is $3.80 per bag.

How To Properly Mix Concrete For Fence Post

There are two schools of thought in mixing concrete for fence post. One method is to actually pour the dry mix directly into the hole with the post in place and add water. This I call the “lazy man way” which we try to discourage. By adding too much or too little, the post will more in likely not set up as intended.

The right way to mix concrete for fence post is to use a wheel burrow, pouring in several bags at a time and slowly adding water while mixing the concrete by constantly turning it over. The secret when mixing concrete for fence post in a wheel burrow is to not add too much water. Too much water makes the concrete soupy and dilutes the strength of the concrete.The look your going for is when the concrete has a look of pan cake batter.

Facts And Myths Of Concrete For Fence Post

Let’s address some of the myths of installing post in concrete.

  • You need to add gravel to the bottom of your post holes.
  • Using the dirt from the hole you dug works just as well as using concrete.
  • Concrete over time will rot out wood post.
  • Once the post are set in concrete, you need to brace each post for several days while the concrete cure.
  • You should only set post when the ground is not frozen.

Here is our rebuttal to these five myths.

  1. Adding gravel to the bottom of the hole (for drainage purposes) really doesn’t accomplish anything. When pouring in the wet concrete into the hole with the post in place, mixes with the gravel, hardens which would affect the drainage. Besides, it’s not like water is seeping down through the post anyway
  2. Reusing the dirt from the hole and tamping firmly around the post is an easy way temporary  secure your post, concrete creates a more solid foundation. Like most areas, we get high winds here in Longmont and Greeley and over time especially for 5′ and 6′ fences, the post constantly rock back and forth creating a void around the post which causes the post to start leaning.
  3. There is some truth to this statement but you can prolong the rotting of the post indefinitely by two ways. We sell a product called Moisture Wrap that we sell here at Cedar supply. It’s a wrap that you install on the bottom of the post which prevents water from coming into contact with the post as well as the acid that is found in some species of post such as cedar. You can also use roofing felt which accomplishes the same thing. Here’s a tip. When filling your concrete up to the top of the hole, add a little more so that it’s slightly mounded which helps the water to run away from the post.
  4. The big myth. If the concrete is mixed properly (pan cake batter texture) your post will not need bracing. You just can’t set you post on windy days.
  5. Actually you can set post year around even if there is a frost line.By adding several scoops of calcium carbrinate to your concrete mix, this product retains heat in the concrete longer and speeds up the curing in the concrete.

Hopefully this information will help you when setting post in concrete.