Your Guide to Types of Deck Footings
December 27th, 2022 by Alexis Camelio
When you’re planning to build a deck for your home, you need to consider several factors before you begin any work—like what kind of wood to use, where it should be placed, and who’s going to construct it. But one of the most important technical considerations that some people overlook is the type of deck footing you need to install.
There are several different types of deck footings to choose from, each suited for different uses. The type you pick will depend on your answers to a few questions. For example, is your deck going to be attached to your house, or is it going to be a standalone structure? What are the building codes in your area? How tall and wide is your structure going to be? All these details will help you decide on the right type of deck footing to install.
Not sure where to start? We’re here to help you make the right choice so you and your family can have a safe outdoor deck for years to come.
Deck Foundations: What Is Deck Footing?
Deck footing is a structure that serves as a sturdy foundation for your deck. They are how your deck connects with the ground, so they’re key to having a firm, secure deck.
Only very small decks that are close to the ground can go without this kind of support. If you have a large surface that’s going to be supporting a lot of people and furniture, you will need to build a footing.
Why Is Deck Footing Important?
A deck footing will ensure that your deck doesn’t tip or cave in after installation. Footing prevents your deck from rotting away by keeping it high and dry above land.
Deck footings are also required by certain legal codes and regulations, depending on your city. If you neglect to add the proper footing, you could face trouble with your local government—or your deck could even collapse.
What Are the Different Types of Deck Footings?
There are various methods and materials to use when building your deck footing. Each one serves different purposes and falls into different budgets. Let’s go over a few different techniques and materials you can use.
Precast Cement Blocks
Precast cement blocks are probably the cheapest and easiest footings to install.
Each block is buried right beneath the ground’s surface. The blocks should be placed close together, so you may end up needing quite a few blocks even for a small deck. Every block has a convenient notch that you can fit ground-treated lumber into.
Precast cement blocks are an affordable option if you have a deck that is close to the ground and not attached to your house.
However, they’re not the strongest or most durable, and they may not meet building codes in certain cities. Be sure to check your area’s regulations before you spend the time and money on the installation process.
Pros of Precast Cement Blocks
- Easy to install
Cons of Precast Cement Blocks
- May not meet regulations in your area
- Will not be effective in areas with high winds
Poured Concrete Footings
This footing material involves digging a hole and pouring concrete directly into the ground. Poured concrete footings can be very labor-intensive depending on where you live.
The first step involves digging a deep enough hole below the frost line. The DIY Network notes that the frost line in most areas is usually between 36 and 48 inches. In some northern states, the frost line can be as deep as 70 inches.
Once you’ve dug a hole of the appropriate depth, you will pour concrete into it. This will form a strong pillar. You can attach your deck’s posts to the top of each pillar using metal brackets.
During the pouring process, you can either pour the concrete in on its own or use a cardboard form to help guide what you’re doing.
Even though they take a lot of work to build, concrete footings are some of the strongest materials available. They are ideal for large decks that are high off the ground. They are also perfect for supporting the weight of a hot tub or other large items.
Pros of Poured Concrete Footings
Cons of Poured Concrete Footings
- Difficult work
- Concrete takes time to fully dry
Precast Stackable Cement Footings
Precast stackable cement footings are similar to the previous method. However, they do not require any pouring on your part. You don’t have to worry about mixing the concrete, achieving the right consistency, or pouring it into a hole.
You’ll still need to dig a deep enough hole and drop the heavy pieces into place. Once you stack each piece on top of one another, you’ll be left with a permanent structure that will keep you and your family safe.
Pros of Precast Stackable Cement Footings
- Permanent and durable
- Quick installation process
Cons of Precast Stackable Cement Footings
- High material cost
- Materials are difficult to transport
Buried Post Footings
Buried post footings are a lot like the poured concrete ones, but they’ll save you some labor.
To start, you will need to dig below the frost line so you will have space to pour the concrete footing.
Once you pour the concrete, you will secure a pressure-treated wood post to it. The entire process doesn’t require as much concrete as the first method, so you will save a lot of time and money.
Because of its concrete base, this footing method still rewards you with a solid deck that can support a lot of weight.
Pros of Buried Post Footings
- Cheaper than traditional poured concrete footings
- Less labor-intensive
Cons of Buried Post Footings
- Concrete takes time to fully dry
Screw piles, also known as helical piles, are manufactured footings made of steel. They screw down into the ground below the frost line.
To install them, you need hydraulic machinery. Because most people don’t have this kind of equipment lying around, you’ll need to recruit a professional’s help.
If you want to take on the building process yourself, this is not the best technique to use.
If screw piles are the kind of footing you want to use, our team can get you in touch with a contractor in your area to install screw piles for your deck.
Pros of Screw Piles
- Won’t disturb your soil
- Fast installation
Cons of Screw Piles
- You can’t install this material yourself
- Very expensive
What Is the Best Footing for a Deck?
With the different types of deck footings, it can be challenging to know which ones are best for your deck. And the truth is, the best footing for your deck may not be the same as the one for your neighbor’s deck.
You’ll find that poured concrete footings tend to work best for many homeowners. However, there are several factors you must consider to determine the deck footings that will be best for your deck.
Freestanding vs. Attached
First, identify whether your deck will be attached to your house or freestanding (floating). Attached decks benefit from having a solid foundation similar to the home’s foundation, so you want to consider poured concrete footings.
Next, survey the soil conditions where your deck will be. Softer soils (like clay) cannot support as much weight without wide footing holes. Wide footing sits below the frost line and supports the entire deck foundation. Buried post footings can be helpful for soft soils with decks that require moderate to high levels of support.
Digging into harder soils (like gravel) requires more labor and professional machinery like augers (hole diggers). If you have hard soil and a deck that requires substantial foundational security, screw pile footings may be best.
It’s a good idea to examine the property’s slope to know how much hold the foundation needs to give. The steeper the slope, the stronger the footings you need, especially where the posts are taller. In this instance, poured concrete footings are an excellent option for a secure and level deck.
Deck Height and Size
Finally, consider your deck’s height and size. A deck higher than ground level or on the second floor will require additional stability since there is more space between the footing and the deck surface. Also, the bigger the deck, the sturdier the foundation will need to be to carry more weight.
If you have a small, low-to-the-ground deck carrying light weight, then you can install deck block footings. Cement or concrete blocks are also viable for small decks that aren’t far off the ground. This is especially true for freestanding decks on flat-graded soil.
Poured Concrete Footings
As mentioned, poured concrete footings remain a popular choice for deck builders because they stand up to the test of time. They have been used for decades to secure various types of decks. Decks that need several layers of fortification should use poured concrete footings. This includes the following:
- Decks with an outdoor bar area or hot tub
- Extra-large decks
- Second-story decks
- Decks built in soft soil
- Decks built on a steep slope
Carefully consider the ideal functionality of your deck to better understand which footings will be best.
A final important note is to always consult your local building codes before beginning any deck construction. The regulations will outline restrictions and expectations in your municipality regarding the deck footings you should use.
Do Deck Footings Need Rebar?
Most deck foundations don’t require the use of steel reinforcing rebar in the footings. However, rebar is typically necessary for decks in expansive or unstable soils, to prevent cracking.
Additionally, rebar is also a good idea if you need to pour your concrete deck footings more than 12 inches above grade or if your deck is on a steep slope that is subject to erosion.
Although rebar is often not required, using it within the deck footing is an inexpensive and easy way to increase deck performance and stability. So if you can add a bit more to your home improvement budget, it’s something to consider. This is especially true for decks with heavy-weight loads.
When used, you should completely encase the rebar in concrete by a minimum of three inches on all sides. Further, don’t let the rebar protrude out of the footings because it increases the likelihood of corrosion. Any corrosion will weaken the deck footing and cause cracking.
How Thick Should Deck Footings Be?
Most experts would say concrete deck footings should be at least six to eight inches thick, and the bottom of the footing should extend below the frost line. Most deck builders use a diameter between eight and 24 inches, with 12-inch diameter footings being the most popular.
The required thickness of your footings will depend on:
- The maximum tributary area allowed per post
- The soil bearing capacity
- The live load
- The dead load
For example, based on 2000 pounds per square foot soil bearing capacity (the amount that sand can support), 40 pounds per square foot live load, and ten pounds per square foot dead load, if the maximum tributary area allowed per post is 56 square feet, you’ll want to 15-inch by 15-inch squares with a 16-inch diameter. But building in harder soil (up to 3000 pounds per square foot soil bearing capacity) could allow you to use slightly smaller or fewer footings depending on the deck design and size.
To better understand how thick your deck footings should be, speak with one of our professional deck builders. They can answer all your questions regarding how to build a deck.
How Many Footings Do You Need for Your Deck?
As with everything else we’ve discussed, the number of footings you need depends on the deck design and size, as well as the size of your beams. Larger beams and footing sizes require fewer footings.
In most cases, you want to position footings and posts less than eight feet apart from center to center. If you plan on installing any heavy items on your new deck, like a hot tub or a porch, you will need more footings and posts to support the additional weight.
Freestanding decks with a ledger board will need an additional beam and row of footings. Decks with many angles also need additional footings.
A basic attached deck foundation of 12 feet by 12 feet requires three 12-inch diameter deck footings. It will need at least two more if you build attached stairs.
You can use a footing and beam calculator to help you determine how many footings will be best for your deck design. You’ll need to know the following to get an accurate calculation:
- Beam span
- Deck footing size
- Joist span
Have Questions About Building a Deck? Contact Us!
The type of deck footing you use is integral to the finished product. If you still have questions or need help from a pro, contact us, and a member of our team can assist you.
Here at Decks & Docks Lumber Company, we are dedicated to helping homeowners construct their dream decks safely. We supply all of the materials you need to get the job done efficiently.
If you’re interested in building a deck or have questions about which materials to use, reach out to us today!
- About the Author
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Alexis is truly a jack of all trades. She has worked for Decks and Docks for over five years where she served as an Assistant Manager before moving into Outside Sales. Alexis has also helped us open multiple stores along the Eastern Coast of Florida and has acted as Manager at a few locations throughout the years. When she’s not working at Decks and Docks, she’s volunteering at a local animal shelter.