Deck Foundation Options: The Ultimate Guide to Foundations and Footings

Deck Foundation Options: The Ultimate Guide to Foundations and Footings

Feb 06, 2024

Selecting the appropriate foundation is one of the most important decisions you’ll make when building a new deck. The foundation determines your deck's stability, durability, and overall success.

Today's various deck foundation options cater to different needs, environments, and designs. From the traditional poured concrete footings to innovative screw piles, each type of foundation has its unique set of characteristics, advantages, and challenges. Whether planning a cozy space for family gatherings or a robust platform for social events, understanding and choosing the right deck foundation is pivotal in bringing your outdoor vision to life.

Deck Foundations and Footings: Quick Overview

  • Poured Concrete Footings: Involves digging holes and filling them with concrete.
  • Precast Cement Blocks: Preformed concrete blocks set on the ground.
  • Precast Stackable Cement Footings: Modular, stackable concrete blocks.
  • Buried Post Footings: Burying pressure-treated wood posts directly in the ground, often with a concrete base.
  • Screw Piles: Steel shafts with helical flights that are screwed into the ground.
  • Easy Deck Footings: Various plastic solutions are easier to set up than other foundation types.

Types of Deck Foundations

There are several types of deck foundations, each with its own set of characteristics, advantages, and drawbacks. Understanding these options is crucial in making an informed decision that aligns with your deck design, location, and environmental factors.

Poured Concrete Footings

Overview: Poured concrete footings are a traditional and widely used foundation type. They involve digging holes to a specified depth (usually below the frost line) and filling them with concrete. These footings are known for their strength and stability.


  • Durability: Concrete is robust and long-lasting, ideal for supporting heavy structures.
  • Stability: These footings are less prone to shifting and excellent for decks requiring a solid base.
  • Customizable: Depending on the deck's requirements, this can be tailored to various sizes and shapes.


  • Labor-Intensive: Digging and pouring concrete is physically demanding and time-consuming.
  • Permanent: Once installed, they are difficult to adjust or move.
  • Weather Dependent: The pouring and curing process can be affected by weather conditions.

Suitability: It is best for large, permanent structures, especially in regions with deep frost lines or unstable soil conditions.

Precast Cement Blocks

Overview: Precast cement blocks, or deck blocks, are preformed concrete blocks set on the ground to support the deck. They are a more straightforward and less labor-intensive option.


  • Ease of Installation: These blocks can be placed directly on the ground without extensive digging or concrete pouring.
  • Cost-Effective: Generally cheaper than pouring concrete footings.
  • Adjustable: Can be moved or adjusted relatively easily if needed.


  • Limited Support: Not suitable for heavy structures or decks with significant elevation.
  • Ground Movement Susceptibility: This can shift over time, especially in areas with freeze-thaw cycles.
  • Code Restrictions: These may not meet building code requirements in some areas.

Suitability: Smaller, ground-level decks are ideal, particularly in areas with stable soil and mild climates.

Precast Stackable Cement Footings

Overview: These are modular, stackable concrete blocks that create a footing. They are an alternative to pouring concrete, which balances strength and ease of installation.


  • Strength and Stability: Provide a solid foundation similar to poured concrete.
  • Modular Design: Allows for flexibility in height and size.
  • Less Labor-Intensive: Easier to install than poured footings, with no waiting for concrete to cure.


  • Cost: Generally more expensive than simple precast blocks.
  • Weight: The heavy blocks may require machinery or multiple people to install.
  • Soil Requirements: Stable, level ground is needed for proper installation.

Suitability: A good option for medium-sized decks, especially when digging deep footings is challenging.

Buried Post Footings

Overview: This method involves burying pressure-treated wood posts directly in the ground, often with a concrete base for added stability.


  • Simplicity: Easier and faster to install than full concrete footings.
  • Cost-Effective: Less expensive than poured concrete footings.
  • Natural Aesthetics: Wood posts can blend seamlessly with the deck structure.


  • Durability Concerns: Wood in contact with soil can be susceptible to rot and insect damage.
  • Maintenance: This may require more upkeep over time.
  • Limited Lifespan: Generally, do not last as long as concrete footings.

Suitability: Suitable for decks that are not too high off the ground and in areas with low moisture and pest activity.

Screw Piles

Overview: Also known as helical piles, these are steel shafts with helical flights that are screwed into the ground. They are installed using specialized equipment and provide a robust and stable foundation.


  • High Stability: Excellent load-bearing capacity and resistance to shifting.
  • Quick Installation: Can be installed faster than poured concrete, with immediate load-bearing capability.
  • Versatile: Suitable for a wide range of soil types and environmental conditions.


  • Cost: Generally, it is more expensive than other options.
  • Equipment Requirement: Requires specialized machinery for installation.
  • Professional Installation: Typically requires hiring a professional, which adds to the cost.

Suitability: It is ideal for decks requiring a deep, stable foundation, particularly in areas with challenging soil conditions or elevated structures.

Easy Deck Footings

For smaller or less complex decks, such as ground-level patios or temporary structures, easier footing options like precast cement blocks and deck blocks are often sufficient.

Instadeck Systems

  • Installation: The Instadeck System features a plastic foundation that you lay on a flat surface. Then, you place deck boards on top of it and step on them to lock them into place.
  • Advantages: They are cost-effective and easy to install, making them ideal for DIY projects. They are also adjustable and can be repositioned if needed.
  • Limitations: They are not suitable for decks of significant height or weight. They may shift over time, especially in areas with freeze-thaw cycles.

Plastic Deck Blocks

  • Installation: Like precast cement blocks, plastic deck blocks are placed on the ground and can directly support a wooden frame.
  • Advantages: Quick and easy to set up, requiring minimal tools and labor. They are relatively inexpensive.
  • Limitations: Like precast cement blocks, they are not ideal for high or heavy decks, and stability can be an issue in uneven or soft soil conditions.

Understanding Deck Foundations

At its core, a deck foundation is a structural base that distributes the deck's weight evenly and securely to the ground. It's designed to anchor and support the deck, ensuring it remains level and stable regardless of weather conditions or weight. The foundation is pivotal in preventing the deck from sinking, shifting, or collapsing, making it a critical component of deck construction.

The primary purpose of a deck foundation is to safely and efficiently transfer the load from the deck to the ground. This load includes not just the weight of the deck structure itself but also the additional weight of furniture, people, and anything else that might be placed on the deck. A well-designed foundation considers the soil type, climate, frost lines, and moisture levels of the location, ensuring that the deck remains stable and intact throughout the seasons.

A foundation well-suited to its environment and constructed with precision can significantly extend a deck's life. It does so by preventing issues such as wood rot, which can occur when the deck is in direct contact with soil, or shifting and cracking, which can happen if the foundation is not adequately aligned with the frost line in colder climates.

Deck Posts: In-Ground vs. On-Footing

The decision between placing deck posts directly in the ground versus on footings is crucial and has significant implications for the deck's stability, durability, and maintenance.

In-Ground Deck Posts

  • Installation: Involves embedding the deck posts directly into the soil. This method is generally more straightforward and less costly than using footings.
  • Stability: It can become less stable over time, especially in areas with shifting soil or extreme weather conditions. Direct soil contact can lead to issues with rot and pests.
  • Durability: The lifespan of in-ground posts is typically shorter due to their increased exposure to moisture and soil organisms.
  • Maintenance: Requires frequent inspection and potential replacement due to the risk of decay.
  • Legal and Safety Considerations: Many local building codes do not permit this method for structural support due to its instability and potential safety risks.

Deck Posts on Footings

  • Installation: Requires the construction of footings (such as concrete piers) above or below the frost line onto which the posts are mounted.
  • Stability: Offers superior stability and is less prone to shifting, as the footings are designed to handle soil movement and weather changes.
  • Durability: Generally, have a longer lifespan since the posts are not in direct contact with soil, reducing the risk of rot and insect damage.
  • Maintenance: Easier to maintain due to reduced exposure to harmful elements.
  • Legal and Safety Considerations: This method is widely accepted and often required by building codes, providing a safer and more durable structure.

A Note on Deck Post Footings

Deck post footings are essential in deck construction, serving as the primary support structure for the deck posts.

Explanation and Importance

  • Deck post footings are designed to distribute the deck's weight evenly and securely to the ground. They prevent the deck from sinking, tilting, or collapsing, especially in areas with unstable soil or severe weather conditions.
  • The footings are typically concrete and either poured in place or precast. They are placed below the frost line to prevent movement due to freeze-thaw cycles.
  • The stability and longevity of the entire deck structure heavily depend on the quality and suitability of these footings.

Installation Tips

  • Depth and Size: Ensure the footings are deep enough to extend below the frost line and are of appropriate size to support the deck's weight.
  • Level and Alignment: Keeping the footings level and properly aligned for even weight distribution is crucial.
  • Quality Materials: High-quality concrete and reinforcement materials ensure strength and durability.


  • Regularly inspect the footings for cracks or shifts in position.
  • Keep the area around the footings clear of excessive moisture or debris to prevent erosion or water damage.

Choosing the Right Foundation for Your Deck

Selecting the appropriate foundation for your deck hinges on several critical factors. Local building codes should be your guiding principle, as they dictate specific requirements and standards. The size and design of your deck also play a pivotal role; larger, heavier structures demand more robust foundations.

Consider your area's environmental conditions, including soil type, climate, and frost line depth. Each of these elements influences the suitability and effectiveness of different foundation types, making it essential to evaluate them carefully to ensure the safety and longevity of your deck.

Once you’ve chosen the best foundation, you can consider other elements, such as the deck railing, and any decorative elements, such as stone veneer panels or stylish porch posts.

Final Thoughts on Deck Foundations

The foundation of a deck is much more than a mere structural component; it's the basis of your deck's stability, durability, and safety. The right foundation choice can mean the difference between a deck that endures for decades and one that encounters problems early in its lifespan. Still, you’ll need to keep your deck clean and well-maintained to ensure its longevity.

Given the complexity and importance of this decision, consulting with professionals is highly recommended. They can provide tailored advice based on your specific circumstances, ensuring that your deck meets all necessary regulations and stands the test of time, providing a safe and enjoyable space for years to come.