There is no need to become overwhelmed when you arrive at your local building supply store and see huge massive isles filled with all of the different types of concrete and cement.
The grade of concrete that you’ll need for a vinyl fence installation is probably the same grade that your store sells in massive bulk, it might even be stacked outside and cluttering up your store’s contractor entrance.
To install vinyl fence posts, you will only need to choose between two types of concrete premix: High-Strength or Fast-Setting. Both options are affordably priced and have a blend of cement, sand and aggregate that will work perfectly for your vinyl fence. Additionally, building supply stores will likely only carry one prominent brand in bulk, Sakrete or Quikrete.
There is no need to get lost with all of the different concrete variations and performance qualities with products like: thin-set, grout, leveling, bonding, crack resistant, water stop, water plug, foundation plaster, patching, and other variations of concrete.
Just walk up to the checkout counter and say, “Ring me up with 20 bags of 80lb crete please.”
That’s it. Really. Just load up the truck and go.
Unless you want to know more about concrete basics and what a vinyl fence installation project will mean in terms of concrete, you can be done reading and can get to work.
What is the difference between cement and concrete? Knowing Helps you to NOT feel like a noob
The terms cement and concrete are often used interchangeably. However, cement is a dry powder mixture of chemicals that will react with water to set, harden, and bind together different materials.
In construction, the mixture of cement, sand and gravel is called concrete. Manufacturers bag up different variations of concrete into “pre-mix” or “ready-mix” bags ready to be hauled directly to your job site. Just add water–and they are ready to install.
High-Strength vs Fast-Setting ? Will you need BOTH?
First, understand that fast-setting concrete is also designated to be a high-strength grade as well. However, fast-setting concrete has an additional chemicals mixed in that greatly speed up the curing process when it reacts to water. This could be beneficial for certain components of your project.
| Concrete Type | Price per bag | Initial Set Time | Foot Traffic | Vehicle Traffic | Max Cure |
| High-Strength 60lb bag | $3.85 | 2-3 hours | 48 hrs | 7 days | 28 days |
| Fast-Setting 50 lb Bag | $5.50 | 10-30 Min | 4-6 hrs | 48 hrs | 28 days |
*Price figures are examples only. Set times can vary depending on temperature, humidity, and water/mix ratios.
As you can see, the fast-setting concrete sets much quicker than the standard mix. However, due to the cost difference between the two, running a fast-setting mix of concrete for your posts can add $6.00 to $8.00 per post hole.
What Posts do you Install First when Building a Vinyl Fence:
Typically, when installing fence, end posts, corners and gate posts are installed first. It would make sense to install these with a fast-setting concrete mix–from which, you could turn right around and run a stringline for plumb and alignment.
Also, if you have a stretch of fence that is completely level, installing both ends of this section with a fast-setting concrete will allow you to quickly plumb and align all of the line posts off of them.
All other line posts can be set with regular mix–really not needing any reason for a rapid set. Unless you have multiple people helping you, it’s not likely that you’d be able to dig holes, set posts, and install pickets’n’rails all in one day.
*Ideally, you’ll want to install your posts on the same day that you dig your holes. Post holes tend to fill back up with dirt during the night because of the evil wicked nasty post-hole-fairy (i.e. your neighbor’s dog or sprinkler system).
Nearly all postholes, for one reason or another, will have to be dug out again to some extent if left overnight. Digging out an already dug posthole is extremely damaging to the psyche.
Pros and Cons of High-Strength and Fast-Setting Concrete Pre-mix
What follows is a list of Pros and Cons between High-Strength and Fast-Setting concrete to help you plan and prepare for your fence install.
High-Strength Concrete Mix:
PROS
- Very Strong and Very Versatile: Used for foundations, footings, sidewalks, patios and…perfect for vinyl fence posts.
- Easy to Work With: Allows plenty of time to maneuver and set posts–even the most stubborn vinyl fence posts. Just add water to your mix if your batch starts getting too dry to work with.
- More Affordable than Rapid-Set: Usually will cost one or two dollars less per bag compared to a fast-setting mix. The high-strength (non rapid-setting) bag is usually one of the cheapest bags of concrete sold at the store.
- Multiple Weighted Purchase Options, such as: 40lb, 50lb, 60lb or 80lb Bags: Having this option can make the job easier–depending on your specific needs and weight-bearing capabilities.
CONS
- Non Load-Bearing and No Duress for minimum of 24 hours: Once the post is installed, you will not be able to install your rails or pickets for a minimum of 24 hours. However, you might be so tired from installing the posts, you might choose to install rails and pickets on the next day anyways.
- May Require Higher Maintenance: If you mix your high-strength concrete too wet, your post will likely slide out of plumb or alignment. You may have to come back several times to make sure your post is still inline and plumb for 30 minutes to an hour after the post has been installed.
- More Labor Intensive: The high-strength concrete will need to be mixed with water in a wheelbarrow or a cement mixer (preferred). You can mix it in the hole–most contractors do. But, it is a bitch to mix. Grunt laborers will switch off–who pours and who mixes because the most useful tool to mix with is a heavy-as-hell Pencil-Point-Post-Hole-Digging-Bar.
- Each Pour Must be Tamped and Consolidated: After the concrete has been added to the hole and the post has been set, the concrete must be tamped and consolidated to remove air pockets. Afterward tamping, the post will again need to be realigned and plumbed.
RAPID or FAST SETTING CONCRETE
PROS
- Sets Quickly: The fast-setting premix concrete will harden enough to be able to set and walk away from the post within just a few minutes. Setting occurs within 30 minutes.
- Fast-Setting Requires No Mixing: Whaaaaat? Yep, that’s right. A fast-setting concrete mix, or rapid-setting concrete mix, does not require mixing with water. It requires water, but, no mixing. Just simply fill ⅓ of your hole with water, drop in and align your post and then pour in your bag(s) of fast-setting concrete into the hole and amply around your post. The water will soak its way through the entire mix, without stirring, and the fast-setting premix will set within 30 minutes.
- Very Strong and Versatile: Fast-setting concrete is also high-strength which makes it very versatile. It can also be used for foundations, footings, sidewalks, and patios. It can be open to foot traffic in as little as 6 hours.
- No Mix Post Set (Sakrete)–sets ultra fast: Fastest-setting premix–sets in five minutes. Usually only available through pre-order and is more expensive.
CONS
- More Expensive: More expensive than the bag of High-Strength by one or two dollars.
- Only offered in a 50lb bag: This might mean hauling around nearly double the number of bags into the truck (or minivan–yep, been there, done that), out of the truck, into storage, out of storage, to location. . .more trips can be tedious.
- Fast-Setting May Set Too Fast: Sometimes you’ll run into a bastard posthole or location and the fast-setting mix will prematurely harden and set on you. Running into this issue can spike your blood preasure as you’ll have to pull it all out and start over. Typically, you’ll know before your pour–and you’ll want to use the standard mix instead.
How Much Concrete per Vinyl Fence Post?
The amount of concrete to use per vinyl fence post will depend on the size of the post and the load that it carries. Your manufacturer will provide recommendations, however, these are some general guidelines:
| Post Size | Post Height (above surface) | 50lb Bags Required | 80lb Bags Required |
| 4×4 | 3-4ft double-triple rail9 inch hole | 1.5 | 1 |
| 5×5 | 3-4ft double-triple rail12 inch hole | 2 | 1 |
| 5×5 | 5-6ft semi & privacy12 | 3 | 2 |
As you can calculate, it will require a very hefty amount of concrete to install a vinyl fence–One to two truck loads and 4-5 minivan loads (don’t worry, been there done that).
How Much Concrete are you Going to be Packing? Brace up!
One thing often overlooked is how much weight all this concrete will add up to. Knowing this figure mostly just serves the purpose of earning bragging rights.
Calculate the total weight of your estimated concrete needs. Multiply this figure by the total number of times you’ll be moving the concrete (i.e. loading the truck=1, unloading the truck=2, moving to storage=3, hauling it to site=4, etc).
As you’ll quickly find, you’ll be hauling and mixing, literally, tens of thousands of pounds of concrete–no easy task.
Cut the Concrete Weight: 5 No-Brainers
There are subtle ways to trim the heft. . .they may seem almost silly, but they actually make a big difference.
- Find out if your retailer will deliver your concrete based the number of bags you will be purchasing.
- Purchase concrete on the day you are going to install it.
- Get help.
- Avoid having to move it into a garage or into storage.
- Unload straight from the truck to the concrete mixer, wheelbarrow or into the hole. (i.e. don’t set it on the ground by the hole only to have to lift it back up to mix it in a wheelbarrow or mixer.)
TRUCK>>WHEELBARROW>>HOLE
Support Systems are Useful When Installing a Vinyl Fence
This is a project you will want help with. Do not go it alone. You’ve just calculated the amount of heft and heave associated with the overall project.
I’ve written a whole blog about things to consider before taking on the project here. It really is back breaking labor and I strongly urge you to obtain multiple quotes from contractors in order for you to be able to perform a proper cost savings analysis by doing it yourself. You will also learn a lot from the local contractors that may help you find ways to make the process more efficient and more affordable.