Are Deck Blocks a Good Idea?

Are deck blocks a good idea? They can be for certain small, low, freestanding decks when the design and local building department allow them. But surface-set deck blocks are not a universal substitute for frost-depth footings. In Minnesota, frost heave, soil conditions, deck height, and structural loads all matter. Here’s how deck blocks compare with other foundation options—and when to consider something more substantial.

Potential Risks Associated with Using Deck Blocks

Quick comparison: Deck blocks rest near the surface and may work for certain permitted low, freestanding decks, but can move with freezing soil. Poured concrete footings are designed for the deck loads and local frost-depth requirements, making them a common choice for permanent deck construction. Helical piers are engineered steel supports installed into suitable bearing soil; they can be useful where excavation is difficult, but require an approved design and proper installation. The right option depends on the site, deck design, and local building requirements.

Instability

Due to their relatively small footprint and reliance on the ground’s bearing capacity, deck blocks can be prone to instability. In areas with unstable soil conditions or frost heaves like the Upper Midwest, deck blocks may sink over time, leading to an uneven and potentially unsafe deck surface.

Shifting

As deck blocks are not securely anchored to the ground like alternative foundation options, they can be susceptible to movement, especially in areas with soil that lacks proper compaction or load-bearing capacity.

Lack of Long-term Durability

Deck blocks are typically made of molded concrete or composite materials. Over time, exposure to the elements can cause these materials to deteriorate. Cracks or crumbling in the blocks can compromise the structural integrity of the deck, leading to safety risks and a shortened lifespan for the deck.

Pros and Cons of Deck Blocks

While deck blocks seem to be a popular choice, it’s essential to consider the following pros and cons to make a sound decision.

Pros

The advantages of deck blocks include ease of installation, versatility, accessibility, and cost-effectiveness:

• Ease of installation: Deck blocks are relatively easy to install, requiring minimal excavation and construction expertise. They are a suitable option for homeowners who want to tackle a deck project themselves or for projects with limited time constraints.
• Limited flexibility: Deck blocks can simplify the layout of some small, low, freestanding decks, but they are not suitable for every deck size, height, shape, or load. Confirm the intended use with the building department before designing around them.
• Accessibility: With deck blocks, the deck surface can be built closer to the ground, making it easily accessible for people with mobility challenges or those who prefer a low-profile deck design.
• Cost-effectiveness: Deck blocks are generally more affordable compared to some alternative foundation options. They can help reduce construction expenses, making them an attractive choice for homeowners on a budget.

Cons

From frost heave to limited load-bearing capacity, there are several disadvantages of deck blocks.

• Frost heave: The Upper Midwest region experiences freezing temperatures during winter, leading to frost heave. Deck blocks, with their limited anchoring capabilities, become more susceptible to ground shifting. This makes the deck uneven, compromising its stability and potentially causing safety hazards.
• Unstable soil conditions: Deck blocks rely on the soil’s bearing capacity for stability. In areas with unpredictable soil conditions, such as expansive clay soils, deck blocks may not provide adequate support, leading to an unstable deck structure.
• Moisture and water damage: Constant exposure to moisture can deteriorate the blocks over time, causing cracks, crumbling, or erosion. This can compromise the structural integrity of the deck and require frequent maintenance or early replacement.
• Limited load-bearing capacity: Deck blocks have a limited load-bearing capacity, and larger decks or structures with heavier loads, such as hot tubs or multiple levels, may exceed their capabilities. This can result in sagging or instability, posing safety risks.

Alternative Foundation Options

• Concrete footings: Concrete footings provide excellent stability and durability for decks. They distribute the weight of the deck evenly and are a common choice for larger or more complex deck structures. However, they require more labor and time to install compared to deck blocks.
• Helical piles: These are steel shafts with helical plates that are screwed into the ground. They offer superior stability, making them suitable for decks in areas with challenging soil conditions. Professional installation is typically required for helical piles.
• Engineered footing systems: Approved proprietary footing systems may be an option for some deck projects, depending on the manufacturer’s specifications, soil conditions, loads, and local building department requirements. Steel deck framing is a separate component and does not replace an appropriate foundation.
• Concrete piers: Concrete piers provide good stability and load-bearing capacity. In the Upper Midwest, they can be designed to extend below the frost line to prevent shifting or heaving due to frost. While the installation process may be more labor-intensive than deck blocks, concrete piers offer durability and longevity.

Consulting with professional deck companies near Twin Cities like UglyDeck helps you determine the most suitable foundation option for your deck project. We have the experience and expertise to evaluate site conditions and soil characteristics and ensure compliance with local building codes. Hence, you can expect tailored recommendations and services based on your needs and preferences.

Work With Deck Construction Experts

Deck blocks may be economical for a small, low, freestanding deck where their use is permitted, but they are not a universal substitute for properly designed footings. For more detail, read how to use concrete deck blocks and the perils of using deck blocks.

To ensure you pick the right foundation option and can fully enjoy your outdoor living space, partner with reliable deck companies near Twin Cities like UglyDeck. Consult with our deck construction experts today!