Build a strong base of knowledge about these two foundation types
Block foundations are constructed from concrete blocks, mortar, and rebar.
Poured concrete foundations use wooden forms to shape concrete into a solid structure.
Climate factors, building site conditions, and house size can determine which foundation type is the best choice.
When you’re building a new house, the construction of your foundation is one of the most important decisions you’ll have to make. Concrete foundations can be made from poured concrete or concrete blocks, and each has advantages and drawbacks. Learn the differences between block and poured foundations, the pros and cons of each, and how to choose the right one for your house.
Concrete foundations are commonly constructed in one of two ways: concrete blocks or poured concrete. A block foundation is made up of concrete blocks joined by mortar and often reinforced with rebar to form the foundation walls. A poured concrete foundation uses mixed concrete poured into wooden forms, which cures into solid concrete walls.
Block foundations provide strong vertical compression strength, while poured concrete offers superior lateral strength. Block foundations are more susceptible to leaks, and are more labor-intensive to construct than poured foundations.
Block foundations are commonly found in older homes, particularly those built before the 1970s. These foundations are constructed by stacking concrete blocks and mortar and often incorporate rebar and grout or other filler in the blocks’ holes to offer additional strength and support. Block foundations can support a significant amount of weight, so they’re often used for larger, heavier homes.
| Pros | Cons |
|---|---|
| High weight-bearing capacity | Gaps between blocks can affect strength and stability |
| Easy to transport | Increased risk of leaks and pest intrusion |
| Doesn’t require large, specialized equipment | Longer to construct |
Best For: Large, heavy homes or historic houses
Since a concrete block foundation uses concrete blocks stacked like bricks, the biggest difference is this type of foundation can usually bear more weight than a poured concrete foundation.
Concrete blocks are stacked, so they’re easy to transport to the site location.
The foundation is constructed by hand using blocks and mortar, so specialized equipment isn’t needed.
The disadvantage of concrete block foundations is that, unlike poured concrete, there will be gaps and space between the layers and blocks since they are not seamless.
A mason will use mortar to bond the concrete blocks. Grout can be used to fill the blocks, which helps with reinforcement and insulation and keeps pests at bay. Still, those gaps increase the risk of leaks.
Concrete block foundations take time since each piece has to be applied by hand.
A poured concrete foundation uses wooden forms to shape poured concrete into a solid structure. They don’t have gaps and have limited joints, and they can be poured into any shape. Poured concrete offers strong resistance to lateral pressure from water and soil and is resistant to leaks and cracks.
| Pros | Cons |
|---|---|
| Lack of gaps or joints | Requires specialized equipment |
| Lower chance of leaks | Premade forms may be difficult to maneuver |
| Faster, less labor-intensive installation | Can be more expensive |
Best For: Modern homes or homeowners with a limited timeline
Poured concrete, as it sounds, is poured into a mold so there are no gaps or joints to deal with.
Since the concrete is seamless and solid thanks to the mold design, there is less likelihood of leaks passing through.
It takes less time to pour concrete since it leverages machinery more than human labor to stack bricks.
Poured concrete needs specialized equipment and machinery such as bulldozers and cranes on-site to pour the concrete mix into the mold.
The wooden forms to create the mold are often large and heavy, which may require cranes to install.
Depending on the size and depth of the foundation, poured concrete may cost more than a block foundation.
Concrete foundations, whether block or poured concrete, protect our homes from water, fire, and critters. Choosing a concrete block foundation or poured concrete for a project largely depends on several factors, including how strong the foundation needs to be, the location of the site, the budget, and the timeline.
Some contractors believe a concrete block foundation is better than poured concrete since it can withstand more weight. Others might argue poured concrete walls are stronger and more waterproof thanks to the lack of joints in the wall. Generally, block foundations offer high vertical compression strength, which is useful for a heavy house, and poured foundations perform better under lateral pressure from soil and water.
Something to consider when it comes to strength and longevity is that both a concrete block or poured concrete foundation will be stronger when reinforced with steel. When researching options, ask how the foundation will be reinforced.
While strength, time, and budget are top of mind, something else to consider should be the site’s location and geography. If the site is prone to extreme weather, such as flooding, making sure the foundation is as waterproof as possible will be important. The right foundation design can keep pests out of the interior space and make it harder for them to find shelter.
Since poured concrete doesn’t have any gaps as part of the overall design, it’s usually preferred when these types of weather conditions are a concern.
Several factors play into how long a foundation will last in a home, including weather, but in general, concrete foundations last upwards of 100 years. Since they are literally the foundation of a home, they are built to last. Some contractors might recommend poured concrete since they don’t have any gaps and can withstand pressure better. However, since both rely on concrete as the main material, both options should outlast even the youngest resident in a home.
Factors that can influence the cost of a foundation include the house’s expected size and weight, specifics of the building site, regional cost variations, the depth of the foundation, and more. Concrete block foundations average between $9 and $15 per square foot. A poured concrete foundation with a short stem wall will cost an average of $6 to $12 per square foot, and a poured concrete basement foundation averages between $20 and $37 per square foot.
While there are many projects that lend themselves to doing it yourself, building a concrete foundation is not one of them. Since your home’s foundation is responsible for its stability and structural integrity, you want to make sure the job is done right with the right equipment and that things like drainage and soil grading are done properly. Hire a concrete contractor who specializes in foundations to ensure the project is done safely and up to code.
Choosing a concrete block foundation or poured concrete for your project isn’t a decision to be made lightly since it’s a decision that will have long-term consequences. There are many foundation contractors in your area who can assist with this project. Some factors your contractor will consider is that a block foundation will be more labor-intensive, while a poured foundation requires large, specialized equipment and premade forms.
Because block foundations are made up of many smaller pieces joined together, there are more places where something can go wrong. The mortar that joins the blocks and the grout or filler within them can deteriorate, causing cracks and leaks, and you may need to call in a block foundation repair pro to prevent further damage. The solid construction of a poured foundation reduces the risk of damage from water, soil shifting, and other causes of cracks.
Homeowners who like a modern look may prefer the smooth finish of a poured concrete foundation. This style offers a uniform look that doesn’t detract from a sleek, modern home. Block foundations are common in historic homes, so homeowners who prefer a more classic or authentically historic look may opt for this foundation style. When it comes to aesthetics, the choice between a block or poured foundation comes down to personal preference.
