Building an elevated deck? One of the most important decisions you’ll make is choosing the right footing. The footing is what holds your entire deck up, keeping it stable and safe. If you don’t get it right, your deck could shift, sink, or even collapse over time. But don’t worry—we’ll walk you through everything in the simplest way possible, so you know exactly what to do.
What is a Deck Footing?
A deck footing is the foundation of your deck. It’s what keeps the posts from sinking into the ground and makes sure everything stays level and sturdy. Think of it like the legs of a table—if they’re weak or uneven, the whole thing wobbles. You don’t want that happening to your deck.
Why Choosing the Right Footing Matters
Your deck’s footing is responsible for handling a lot of weight, including the deck itself, furniture, and people walking on it. The wrong type of footing can cause your deck to shift or sink over time. That’s why it’s so important to choose the right one based on your soil, climate, and the height of your deck.
What to Consider When Choosing Footings
There are a few key things to think about before deciding on your deck footings.
- Soil Type: Different soils have different strengths. If your soil is loose or sandy, you’ll need deeper and stronger footings. If it’s clay, it holds water, so you’ll need footings that prevent shifting.
- Deck Height: The taller your deck, the stronger the footing needs to be. A simple ground-level deck doesn’t need much, but an elevated deck needs deep, solid support.
- Weather Conditions: If you live somewhere with cold winters, the ground freezes and expands, which can push footings out of place. If you live in a wet area, too much water can weaken the ground under your footings.
- Local Building Codes: Every area has different rules for deck footings. Some places require footings to be a certain depth, and others might have special rules for safety. Always check your local codes before you start digging.
Types of Footings for Elevated Decks
There are a few different types of footings you can use for your deck, and each one works best in different situations.
Concrete Footings
Concrete footings are the most common and the strongest option. They involve digging a hole, pouring in concrete, and setting your post on top. If you want your deck to last for decades, this is the way to go.
They’re great for decks in most soil types, especially if your area gets cold winters or heavy rain. Just make sure you dig below the frost line (the depth where the ground freezes in winter), so the footing doesn’t shift when temperatures change.
Sonotube Footings
Sonotubes are cardboard tubes that you fill with concrete. They’re easy to use and make sure your footings are the perfect shape and size. You dig a hole, place the tube inside, fill it with concrete, and then place your post on top.
These are great for places where the soil is soft because they help keep the concrete from spreading out and losing strength.
Helical Piers
Helical piers are metal posts that are screwed deep into the ground instead of being set in concrete. They work well in areas with soft or shifting soil because they anchor into the ground and don’t move over time.
They’re more expensive than concrete footings, but they’re faster to install and can be used even in tricky soil conditions.
Deck Blocks
Deck blocks are pre-made concrete blocks that you can place directly on the ground. They’re super easy to use because you don’t have to dig, mix concrete, or wait for anything to dry.
These work best for low-level decks or temporary structures. They’re not strong enough for a tall, elevated deck, especially in areas with soft or wet soil.
How Deep Should Your Footings Be?
The depth of your deck footings depends on your location and soil type. In colder areas, you’ll need to dig deeper to get below the frost line. If you don’t, the frozen ground can push your footings up and cause the deck to move.
A good rule of thumb is to dig at least 12 inches deep for basic decks, but for elevated decks, you’ll want to go 24 to 48 inches deep, depending on your area’s frost line and soil conditions.
How Many Footings Do You Need?
The number of footings depends on the size and design of your deck. Bigger decks need more support, which means more footings. A small deck might only need three or four, while a large deck could need a dozen or more.
To figure out how many footings you need, divide your deck into sections and place a footing under each major support beam. Your local building codes can also give you a guideline for spacing them properly.
How to Install Deck Footings the Right Way
Now that you know the different types of footings and why they matter, let’s talk about how to install them properly. This is a crucial step in building a strong deck, and doing it right the first time will save you from major headaches down the road.
Step 1: Plan the Layout
Before you start digging, you need to figure out where each footing will go. This depends on the size of your deck and the placement of support beams.
- Use stakes and string to outline where your deck will be.
- Mark the spots where each post will go using spray paint or a small flag.
- Check your local building codes for required spacing between footings.
If you’re not sure how many footings you need, a good rule of thumb is to place them no more than 8 feet apart for a standard deck. But if your deck is extra large or elevated, you may need them closer together for better support.
Step 2: Dig the Holes
Once you have your layout planned, it’s time to start digging. The depth and width of your holes will depend on your climate and soil type.
- In warm climates: A depth of 12-18 inches is usually enough.
- In cold climates: You need to dig below the frost line, which could be anywhere from 24-48 inches deep depending on where you live.
- For soft or loose soil: You may need to go deeper or use wider footings to prevent sinking.
The width of the holes should be about 12-18 inches across, but check your local codes for exact requirements. If you’re using sonotubes, the hole should be just big enough for the tube to fit snugly inside.
Step 3: Add Gravel for Drainage
Before pouring concrete, it’s a good idea to add a few inches of gravel at the bottom of each hole. This helps with drainage and keeps water from pooling under your footings, which could cause shifting or sinking over time.
- Pour about 4-6 inches of gravel into each hole.
- Use a tamper or a piece of wood to pack it down tightly.
- Make sure the gravel is level before moving on.
This small step makes a big difference in keeping your deck footings stable for years to come.
Step 4: Pour the Concrete
Now it’s time to set the actual footing. If you’re using sonotubes, place them in the hole first. If not, you can pour the concrete directly into the hole.
- Mix the concrete according to the instructions on the bag. You want a thick, pudding-like consistency.
- Slowly pour the concrete into each hole or sonotube, filling it to the top.
- Use a shovel or stick to stir the concrete and remove any air pockets.
- Set a metal anchor or post bracket into the wet concrete. This will hold the deck post in place once it dries.
Let the concrete cure for at least 24-48 hours before moving on to the next step. In colder weather, it may take longer.
Step 5: Attach the Posts
Once the concrete is fully set, you can attach the deck posts. If you used metal brackets, simply place each post into the bracket and secure it with screws or bolts. If you didn’t use brackets, you may need to drill into the concrete to attach the post.
- Use pressure-treated wood for the posts to prevent rot.
- Check for level to make sure each post is straight before tightening the bolts.
- Double-check your spacing to ensure everything lines up properly before building the rest of the deck.
This is where taking your time pays off. If the footings aren’t level or properly aligned, your entire deck could end up crooked.
How to Strengthen Your Deck Footings
Even if you install your footings correctly, there are a few extra steps you can take to make them even stronger.
Use Rebar for Extra Strength
If you’re using concrete footings, adding rebar can help prevent cracking and shifting over time.
- Place two or three pieces of rebar vertically into each hole before pouring the concrete.
- This helps the concrete hold its shape and prevents movement, especially in areas with extreme weather.
Seal Wooden Posts to Prevent Rot
If your deck posts are sitting directly on concrete, moisture can build up and cause rot over time.
- Apply waterproof sealer or a post protector around the base of each wooden post.
- This helps keep water from seeping into the wood and extends the life of your deck.
Check Your Footings Every Year
Even the best-built decks need occasional maintenance. Make it a habit to inspect your footings once a year to catch any issues early.
- Look for cracks in the concrete or shifting posts.
- Check for signs of rot or insect damage on wooden posts.
- If your deck wobbles, it might mean the footings are starting to move. Fixing this early can save you from bigger repairs later.
How to Fix a Shifting Deck Footing
If you notice your deck footings sinking or shifting, don’t panic! There are ways to fix the problem before it gets worse.
1. Add More Support
If your deck is sagging in certain areas, you can add extra footings or support beams underneath to help redistribute the weight.
2. Dig and Reinforce
For footings that have moved due to poor soil or frost, you may need to dig them up and pour deeper footings. This is a big job, but it’s better than having an unstable deck.
3. Use Helical Piers
If your soil is too soft for traditional footings, switching to helical piers can give your deck a stronger foundation. These screw deep into the ground and hold up better in shifting soil.
Common Mistakes to Avoid
Not Digging Deep Enough. If you don’t dig below the frost line, your footings can shift over time. Always check how deep you need to go based on your location.
Using the Wrong Type of Footing. If you have soft or wet soil, deck blocks won’t be strong enough. Make sure you choose footings that match your soil conditions.
Skipping Reinforcement. For concrete footings, adding rebar or metal brackets helps strengthen the foundation and keeps the deck more stable.
Ignoring Building Codes. Footing rules exist for safety. If you don’t follow them, your deck might not pass inspection, or worse, it could become unsafe over time.
Which Footing is Best for Your Deck?
The best footing for your deck depends on your situation. If you want the strongest and longest-lasting option, concrete footings or sonotubes are the way to go. If you have soft or shifting soil, helical piers might be worth the investment. If you’re building a simple, low deck, deck blocks can work, but they’re not ideal for anything elevated.
Choosing the right footing might seem complicated, but once you know what to look for, it’s just a matter of matching the right type to your deck’s needs.
FAQ: Choosing the Right Footing for Elevated Decks
What type of footing is best for an elevated deck?
Concrete footings are the most reliable and long-lasting option. They provide strong support and prevent the deck from shifting over time.
How deep should deck footings be?
Footings should be at least 12 inches deep, but in colder climates, they need to go below the frost line, which can be 36 inches or more.
Can I build a deck without footings?
Some small decks can be built on deck blocks, but for elevated decks, proper footings are required to ensure stability and safety.
How do I prevent footings from shifting?
Make sure footings are deep enough, use reinforced concrete, and compact the soil properly before pouring. In some cases, gravel or drainage systems help prevent movement.
Do I need a professional to install deck footings?
If you’re experienced with construction, you can do it yourself. However, hiring a professional ensures proper placement, depth, and stability for long-term durability.
Need Help with Your Deck?
If you want a sturdy, well-built elevated deck that will last for years, you need a solid foundation. At Deck Bros, we specialize in designing and building decks that are safe, strong, and built to last.
Give Deck Bros a call at (402) 369-5724 today to get expert advice and professional deck installation that you can trust. Let’s build the perfect deck for your home in Omaha!