Welcome back to our Deck Design series for June! In this installment, we’ll focus on one of the most critical aspects of building a sturdy and long-lasting deck: the foundation. A well-constructed foundation is essential for the stability and durability of any deck. This post will explore two common types of deck foundations: pad footings and caissons. Understanding the differences between these foundation types, their benefits, and their applications will help you make an informed decision for your deck project.

Understanding Deck Foundations

A deck foundation supports the structure and transfers loads to the ground. The foundation type you choose will depend on various factors, including soil conditions, deck size, and local building codes. The two primary foundation options for decks are pad footings and caissons. Whether you’re designing a simple deck or a more elaborate structure, selecting the right foundation is crucial.

Pad Footings

What Are Pad Footings?

Pad footings, also known as pier footings or isolated footings, are concrete pads that provide a stable base for the deck posts. These footings are typically square or rectangular and are poured directly into the ground.

Advantages of Pad Footings

1. Ease of Installation:
   • • They are relatively easy to install, making them a popular choice for DIY projects and small to medium-sized decks.
2. Versatility:

• • Suitable for various soil types and can be adapted to different deck designs, including simple backyard decks and more complex covered deck designs.

Installation Process

1. Excavation:
   • Dig holes at the locations of the deck posts. The depth of the holes should extend below the frost line to prevent frost heave.
2. Formwork:
   • Place forms in the holes to shape the concrete. The forms can be wooden or pre-fabricated plastic tubes.
3. Pouring Concrete:
   • Pour concrete into the forms, ensuring it is level and smooth. Allow the concrete to cure before proceeding with the deck construction.

Applications

Pad footings are ideal for decks with moderate loads, such as residential decks without heavy features like hot tubs. They work well for decks in stable soil conditions and regions with minimal frost heave. This makes them a versatile choice for various decking designs.

Caissons

What Are Caissons?

Caissons are cylindrical foundations that provide robust support for deck structures. They are typically used in areas with poor soil conditions or where high load-bearing capacity is required.

Advantages of Caissons

1. Simplicity:
   • Caissons are more simple to install than pad footings, and typically require an auger and concrete.
2. Stability
   • They provide excellent stability in challenging soil conditions, including expansive soils and areas with high water tables.
3. Frost Protection

• • Because caissons can extend deep into the ground, they are less susceptible to frost heave, making them suitable for cold climates.

Installation Process

1. Drilling
   • Use a drilling rig or auger to create holes at the deck post locations. The depth of the holes depends on soil conditions and load requirements.
2. Formwork and Reinforcement
   • Insert forms or tubes into the drilled holes and add rebar for reinforcement to increase the strength of the concrete.
3. Pouring Concrete
   • Pour concrete into the forms, ensuring it fills the entire hole and surrounds the rebar. Allow the concrete to cure fully before proceeding with the deck construction.

Applications

Caissons are suitable for large, heavy decks or those with additional features like hot tubs or heavy snow loads. This makes them perfect for complex decking designs, including multi-level decks and covered deck designs.