Concrete deck blocks support decks that are not connected to another structure, so you might be wondering if you can bury them underground. Luckily, we've done the research to provide you with everything you need to know when using concrete blocks.
You can and should bury concrete deck blocks. Concrete deck blocks are commonly buried at least 12 inches underground in the topsoil to comply with local building codes.
Codes may vary from one state to another. Refer to your state's building codes to determine the required depth for burying a concrete deck block.
Concrete deck blocks provide support to freestanding deck structures. They help reduce the movement of the deck during harsh weather. Continue reading as we discuss all the other essential details you will need when using concrete deck blocks.
Can Concrete Deck Blocks Be Buried?
Concrete deck blocks support the posts that will lift the deck. They are concrete blocks with a square body with notches on the top to hold the deck's posts in place.
The flat bottom of the concrete deck blocks is referred to as the object's bearing area. The bearing area provides the foundation for the deck posts by adding a broader base that can sit against the soil.
Concrete deck blocks work as the base of your deck structure. They are considered a type of foundation by building codes. This means that concrete deck blocks can and should be buried underground just like any building foundation.
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The minimum requirement for burying a foundation is 12 inches underneath an undisturbed soil surface. Undisturbed soil refers to soil that has not been excavated, sowed, or plowed before.
Burying concrete deck blocks underneath undisturbed soil enhances the stability of the material. It also helps the soil to hold the concrete block in place.
How Deep Can I Bury A Concrete Block?
While the minimum requirement for burying concrete deck blocks is 12 inches underneath undisturbed topsoil, the actual depth will vary depending on your location.
The depth at which you should bury a concrete block varies because of the diverse climate that can affect building structures in different parts of the world.
Concrete deck blocks can hold the posts of the decks in place, but their sturdiness can still be affected by various weather conditions. This could mean that you will need to bury a concrete deck block deeper than 12 inches if you experience extreme conditions.
Water, temperature, wind, and other conditions can affect the hold of the concrete block on your deck's post. This is because no permanent object usually seals the deck post to the concrete deck block.
Extreme weather conditions can detach the deck from a foundation if it is not secured well under solid ground. Strong wind can move the posts, and frost can heave concrete deck blocks.
In addition to your location's climate, the type of soil where you will bury the concrete deck block will also affect the depth. This is because the texture of the soil will affect the level of support it can give the concrete deck blocks.
For example, concrete deck blocks buried underneath soil susceptible to frost should be below the local frost depth. This means that if you live in an area that experiences snow or frost, you will have to bury the concrete deck blocks deeper than 8 feet.
For sandy locations, the recommended depth would be around 3 feet or until you find stable soil. This depth for deck blocks is ideal for structures built in sand or gravel soil.
Will Concrete Deck Blocks Sink?
Concrete blocks can sink over time. However, this sinking is not exclusive to concrete deck blocks. Sinking structural foundations can happen when the earth underneath erodes due to natural causes. Because of this, concrete deck blocks are not recommended to be used in permanent residential areas.
The bearing area that presses against the soil can cause the ground to erode, especially when there is an uneven weight distribution between all concrete deck blocks on site.
To avoid this in your deck project, it is best to use multiple concrete deck blocks rather than a few. This practice will provide more support to the posts of the deck.
As a result, the deck's weight is distributed to a larger amount of concrete blocks. This reduces the possibility of soil erosion.
Do Concrete Deck Blocks Heave?
Concrete deck blocks can heave if they are buried under unsuitable soil. In addition, the depth of the hole in which they are buried can also cause them to heave.
To prevent concrete deck blocks from heaving, ensure that you have buried the deck block according to your state or country's building code.
For areas that experience frost, again, check your local frost depth. This will prevent the foundation from moving due to frost heave.
Do I Need To Put Anything Under Concrete Deck Blocks?
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You do not need to place anything under the concrete deck blocks other than the soil.
Just as concrete deck blocks act as the foundation of the posts, the soil underneath acts as the foundation of the blocks. This means that the best thing you can do to support your deck well is to build it on good soil.
It is common for concrete deck blocks to shift due to natural movements or weather conditions. While no type of soil is immune to natural change, sand and gravel are the better choices if you want to prevent deck movement as much as possible.
Sand and gravel work best, especially in places that experience frosts. This is because both types of soil can adapt well during frosty seasons and the thawing period that occurs afterward.
Sand and gravel do not retain as much water due to their composition. Both soils keep as much of their original shape even during changing weather.
On the other hand, clay is the trickiest soil to bury a concrete deck block in. Because of its composition, clay soil is susceptible to retaining a lot of water.
Soil water retention can cause a significant change in the size of the soil. When the size of the soil changes, the concrete blocks buried in it will shift with the soil.
Can I Use Concrete Deck Blocks Instead Of Footings?
You can use concrete deck blocks instead of footing. Concrete deck blocks are a type of precast foundation, which refers to the concrete footing of buildings and structures. Both materials are designed to support the beams of a structure.
Concrete deck blocks function the same as footings. The only significant difference between the two is that a concrete deck block is pre-molded, meaning you will have to pack the soil around it rather than the other way around.
For traditional concrete footings, the concrete is mixed on-site and poured into the hole where the other foundation materials will be added. Pre-molded blocks, such as concrete deck blocks, become an easy solution when mixing on-site is impossible.
You can use concrete deck blocks instead of concrete footings when you can't mix concrete on-site or if you are building a deck that is not permanent. Concrete blocks are also convenient for DIY due to their low price.
To Wrap Up
In this article, we discussed if concrete blocks can be buried. We also discussed how deep you should bury the foundation when other factors are considered.
Make sure to build your deck in good soil so that you can enjoy a sturdy outdoor space. Concrete deck blocks should be secured under untouched soil. The soil anchors the concrete blocks, providing sturdiness to the foundation and the deck.
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