How to Build Deck Footings?
A deck is the perfect spot for enjoying outdoor living, hosting gatherings, and relaxing. The deck footing directly determines its safety, stability, and lifespan. To build deck footings, you need to mark the location of each footing. Dig holes below the local frost line, then lay a gravel base layer. Finally, pour concrete and insert metal brackets or anchor bolts to secure the posts.
The importance of a foundation cannot be overstated. Improper foundation design can lead to structural failure and even safety hazards. This article will guide you through the construction process of deck footings, helping you build a rock-solid base for your deck.
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Table of Contents
Primary Types of Deck Footings
A deck footing’s job is to spread the weight of the deck over a larger area of soil. If there wasn’t support, the posts’ thin bases would sink into the ground like nails when they were pushed down hard. Every base isn’t right for every situation. Here are some types of deck footings and what’s good and bad about each one:
Embedded Posts and Footings
For this simple method, pressure-treated wood posts are poured straight into holes in concrete. Concrete is poured right into the holes, and then the posts are put into the still-wet concrete.
Cast-in-Place Concrete Piles
This is currently the most common foundation type. It consists of a cylindrical concrete pile. To build a strong base, homeowners must dig down below the frost line, set up formwork pipes, and pour concrete. Once it’s hard, metal pieces like post brackets or support bolts are put on top to hold the wooden posts in place. This method works for heavy deck loads and is common in most places where the codes allow it.
Bell-Bottom Piles
Bell-bottom piles represent an enhanced form of poured concrete piles. They offer superior load-bearing capacity and frost heave resistance. A specialized plastic mold creates an enlarged, bell-shaped base at the pile’s bottom. This expanded area distributes loads over a larger soil surface. Additionally, it more effectively counters upward lifting forces from frozen ground.
Auger-Driven Piles
This foundation system is installed by specialized contractors. To do this, special tools are used to drive long metal piles with helical blades into the ground like screws until they hit the right bearing layer. This method doesn’t change the site too much. It works especially well on hills, rocky ground, or places where digging is hard. The bad thing is that the equipment and skilled installation are very expensive.
What Preparations are Needed before Constructing Deck Footings?
Before commencing construction, thorough planning and preparation are essential. Key steps include:
Obtain Necessary Permits
In most areas, building permits are required for deck construction. Ensure your project meets safety standards. Contact your local building department before starting any work. Verify local regulations regarding foundation depth, diameter, and type.
Locate Underground Utilities
Various lifelines may be buried beneath your planned excavation area, including:
- Gas lines
- Electrical lines
- Water mains
- Sewer lines
- Communication cables
- Private utilities (e.g., landscape lighting lines, propane lines)
Hitting any utility line can cause serious injury and result in substantial liability. Therefore, locate and mark all underground utilities before planning any excavation.
Clear and Mark the Site
Get rid of all the plants, rocks, and other junk that are on the deck. To make drainage easier, the land should slope a little away from the house. Then, using pegs and string, carefully trace the design plan’s outline around the deck’s outside.
Put a stake in the exact spot where each base will go. Lastly, use diagonal measurements or other ways to check the horizontal and vertical distances of all the points.
Prepare Tools and Materials
Typically, the following tools and materials are required for deck footing construction:
- Digging Tools: Round-tip shovel, post hole digger, crowbar. Renting an electric auger or post hole digger can significantly reduce physical effort.
- Concrete Supplies: Concrete form tubes, ready-mix concrete, crushed stone, buckets, mixing tools.
- Fasteners: Galvanized or stainless steel post brackets, J-bolts.
- Measuring and Leveling Tools: Tape measure, level, plumb bob, carpenter’s chalk line.
- Safety Gear: Gloves, safety goggles, etc.
Construction Steps for Building Deck Footings
Once you’ve done all of these things, you can officially start building. Taking the pouring of concrete footing foundations as an example, the detailed construction process is as follows:
Precisely Dig Foundation Holes
Determine the centre point of each hole based on the staked-out wooden stakes. Use a hole digger or manual excavation. To allow for adjustments and backfilling, the hole diameter should be a few inches bigger than the width of the formwork pipe. The depth must reach the specified value below the local frost line. Keep the hole walls as vertical as possible and the bottom level. If the bottom soil is disturbed, compact it with tools.
Laying the Gravel Bed
Pour a 4-6 inch thick layer of gravel into the bottom of each hole. Compact and level the gravel using a wooden rammer or tamper. This layer helps the base drain better, so water doesn’t build up and soak the concrete floor. It also provides a level starting surface.
Installing and Adjusting Formwork Pipes
Place the concrete formwork pipes into the holes. The tops of the columns should be a few inches above the finished ground level so that water doesn’t pool around them when it rains. Use a level to ensure the pipes are vertical. Finally, backfill soil around the pipes and compact it to secure their position.
Mixing and Pouring Concrete
Strictly follow the water-to-cement ratio specified on the concrete packaging. Underseated concrete will significantly reduce strength. Pour the concrete into the formwork pipe in batches. To make sure the concrete is packed down, use a long wooden stick or rebar to tamp it down after each pour.
Embedding Anchor Bolts or Brackets
This must be done while the concrete is setting, but not yet fully hardened. First, mark exactly where the anchor bolts will go based on how far apart the holes are in the metal column clamp. Align them with the direction of the next column. Put the bolts into the concrete vertically, leaving enough length to add the nuts and screws. Make sure the height is exactly right by using a level.
Concrete Curing and Final Inspection
Concrete strength development requires a moist environment. Prevent excessive drying within 24-48 hours after pouring. Cover the area with a wet cloth or plastic wrap, and sprinkle water on it every so often to keep it moist. Follow the drying instructions that came with the concrete. Additionally, it is strongly suggested that no building activities occur on the base until the concrete is strong enough.
Common Mistakes and Precautions
Building a foundation requires precision, knowledge, and patience. Below are common mistakes many homeowners make. You must carefully inspect and avoid these.
- Insufficient Depth: The foundation hole is not dug below the frost line. This is the primary cause of future deck problems.
- Ignoring Underground Utilities: It is very dangerous and careless not to find and mark underground utilities.
- Too Thin of a Mix: Adding too much water to make pouring easier greatly lowers the strength of the base.
- Directly Embedding Wooden Posts in Concrete: This makes the deck last much less long and is against current building codes.
- Improper Anchor Bolt Placement: Anchor bolts that are not in the right place stop the column from being properly installed or weaken its ability to hold weight, which makes fixes very hard.
- Lack of Inspections and Permits: This could lead to demolition orders, which could affect your house insurance and its value when you go to sell it again.
Conclusion
The deck footing is the heart and soul of any deck project. A great deck always starts with a solid foundation. You can make a safe and stable outdoor living place if you follow the right building steps. It is much more cost-effective to spend more time and money on the base than to fix the whole deck later. If you’d like to learn more about outdoor decking, feel free to contact us. EVODEK offers premium composite decking materials. We’re here to answer all your questions.
FAQ
Why Shouldn’t Deck Posts be Buried Directly in Concrete?
While this practice was common in the past, modern building codes have phased it out. Key reasons include:
- Moisture Retention and Rot: Where pavement meets wood is where water tends to gather the most easily. This point of touch is still the weakest and most likely to rot, even in pressure-treated wood. Once the base starts to rot, the whole deck’s structure is seriously damaged.
- Lack of Secure Mechanical Connection: The concrete only covers the post; it stays stable mostly through contact. This doesn’t give the deck enough protection against side forces it might face. When bolted into the concrete, special metal brackets make a much stronger mechanical link.
- Code Violation: These days, most building rules make it clear that you can’t bury or cover untreated wood posts directly in concrete. If you use old methods on your job, it might not pass inspection.
How Long Does Concrete Take to Fully Cure?
Most of the time, concrete is strong enough after 24 to 48 hours. You can carefully take down the formwork and side supports, which will let the next phase of building begin. However, moisture curing must be maintained during this period. Furthermore, concrete generally requires 28 days to reach full strength. For deck footings, however, it typically achieves load-bearing strength in about 7 days.
Why is Gravel Placed at The Bottom of Foundation Pits?
The gravel bed serves several critical functions:
- Improves Drainage: Groundwater can’t get straight into the concrete foundation base through the soil because of the gravel layer, which stops capillary action. This makes it much less likely that water will pool at the bottom, especially when the water freezes and thaws.
- Provides a Level Base: It creates a solid, level surface for pouring concrete, particularly in pits that aren’t perfectly excavated.
- Distribute Stress: The gravel also disperses loads more evenly into the underlying soil.
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