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Bedrock & Load-Bearing Strata

Soil or rock that bears the weight of a building without becoming compressed or shifting. The soil is inert and doesn't experience expansion or contraction.

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When building a structure, it’s key to have the right foundation beneath it. This applies to both modest family homes and commercial, multi-floor buildings like hotels and shopping malls. They all need a strong and stable substructure to carry their weight. But despite their ability to distribute the load of the walls equally onto the ground, foundations also need to prevent water from coming inside the lower-grade levels.   

However, not every type of soil is the same. Their physical properties differ, allowing for varying results that will affect the building as a whole. It’s, hence, important for construction crews and engineers to understand geology, topography, and soil composition before they start the building process. Depending on the type of building they’re looking to make, the team will need to closely inspect the ground to see which kind of foundation will best suit the project.  

Read on as we introduce you to bedrock/load-bearing strata. This way, you’ll better understand how foundations work and why it’s important to have strong soil under them. 

What Is Load-Bearing Strata?  

Below the earth’s surface lies a contiguous mass of rock that can support the foundation of your entire building or structure without sinking, settling, or shifting. It’s known as the bedrock or load-bearing strata.  

As well as being inert, bedrock does not contract or expand like the soils on the earth’s surface. However, they can get exposed in places with high erosion.  

When a home lies on sand or clay soils, it may start moving and sinking, and this might cause structural problems. Foundation contractors will underpin the foundation by driving piers down to the bedrock until they meet resistance. At 20 to 55 meters deep, the rock is so dense and can bear the weight that’s transferred to it via piers.  

Types of Bedrock  

Bedrock formation can fall into these three categories.  

Sedimentary rock:

When pieces of rock (sediment) get carried to some basin or depression by air, wind, or water, they get trapped and buried over time. This loose sediment compacts and forms sedimentary rock. The resulting rock tends to be softer than other types of bedrock.  

Igneous bedrock:

Any glassy or crystalline rocks that form when magma or molten lava cools off and solidifies on or below the earth’s surface falls within this category. They form when tectonic forces dislodge and deposit sedimentary rocks or metamorphic rocks into the hot mantle, where they melt and get ejected as magma, which cools off to form igneous rocks.                                                          

Metamorphic bedrock:

Sometimes, bedrock can change due to forces such as heat or reactive fluids like salty water under the pressure of the earth’s crust.  

How Is Bedrock Depth Determined?  

There are many ways of determining the depth of load-bearing strata. Common techniques include digging, desk studies, and drilling. Because the depth of the bedrock varies from place to place, it’s essential to know what type of foundation can provide adequate support to your structure.  

Bedrock and Foundation Repairs  

If you experience settlement at some point in time, your local contractor will move quickly to stabilize your foundation back and potentially lift it back to its original elevation. They do this by driving piers down the ground into the stable bedrock to ensure structural integrity.  

Once the piers meet the load-bearing strata and resistance is established, they are load-tested to determine the proper depth they should be drilled to and the load they can carry. We use a simple math formula to measure torque to capacity while keeping in mind the soil type and their condition as well as the structure’s weight.  

Hydraulic lifts are then attached to your house. By applying pressure simultaneously, less pressure is used during lifting. Finally, the home gets lifted off the active soils and the structural load is transferred to the columns in the bedrock.  

Can You Build a Foundation on the Bedrock?  

Yes, it’s possible where there’s an outcrop or exposed layer of bedrock. But that’s not a common thing. If you were to build your foundation on top of the bedrock, you’d have to dig out tons of soil first. That’s not feasible or cheap for residential purposes.  

If your home’s foundation needs support due to settlement, contact the experts at Groundworks for a free foundation inspection and repair estimate. We’ll send out an inspector to examine your foundation, and one of our crews can carry out the necessary repairs quickly. We use industry-approved and proven underpinning solutions so you’re assured of lasting results. 

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