How Different Soil Types Impact Your Foundation: Ultimate Guide

Soil types and their origins significantly impact their suitability for construction projects. Native soil layers, depending on their composition, can be an excellent choice for building a solid foundation.

This guide explores soil layers and types, their impact on your home, and the foundation repair methods available when needed.

Soil layers are categorized as either natural or artificial. Each layer has unique texture, moisture content, and density characteristics. Natural layers, including topsoil, subsoil, and deeper layers, form over time through wind, water, or glacial activity. Artificial soil layers, such as fill soil, are manufactured for specific construction needs.

As natural and artificial layers accumulate, collect, and compact, they gain density and strength, influencing their suitability for supporting foundation structures.

Understanding soil layers is crucial to ensuring proper home construction and durability. Here’s more on soil layers:

Fill soil is a manufactured mixture of rocks, clay, and sand used in large construction projects and landscaping to level uneven ground around foundations or address drainage issues. Proper compaction testing is essential to ensure its construction suitability, as fill soil is known to settle over time.

Glacial deposits exhibit various particle sizes and are formed when glaciers transport and deposit rock, sand, and clay sediments on land. Some deposits are carried by meltwater and settle as deposits. These deposits can be very valuable for construction. However, the specific composition varies greatly.

Careful professional assessment is needed to determine whether a particular glacial deposit is suitable for a project. This approach ensures proper construction practices and adequate foundation preparation.

1. Sand

Sandy soil is gritty, coarse-grained, and has particles larger than 0.5 millimeters. It is known for its drainage properties; however, it is susceptible to wind and water erosion, especially if it is loose and lacks vegetation. Settlement can occur due to loose compaction and water table fluctuations. Though sandy soil poses challenges, foundation experts can utilize specialized techniques and practices to build foundations on sandy soil.

2. Silt

Silt soil contains middle-sized particles between sand and clay. It is known for its smooth, floury texture. Despite its water retention capacity, it drains well due to the spaces between its fine particles (0.002-0.05 millimeters). This capability makes silt soil suitable for plants and contributes to its role in fertile soil mixtures like silt loam. However, silt is susceptible to wind and water erosion and settlement, making pure silt soil challenging for foundations.

3. Clay

Clay soil is a fine-grained, expansive soil composed of particles smaller than 0.002 millimeters. It forms through sedimentary rock weathering. Clay is rich in zinc, calcium carbonate, mica, and other minerals that give it unique properties, like its sticky, cohesive structure capable of retaining significant amounts of water. The size and mineral content distinguish clay from fine-grained soils like silt. Clay is a natural soil used for various construction purposes, including making bricks and tiles. Expansive clay soil causes foundation damage due to its expansion when wet and contraction when it dries out.

4. Loam

This naturally occurring soil type is a balanced mix of sand, silt, and clay. It is ideal for gardening and agriculture due to its well-draining aeration properties. However, loam is not recommended for foundation support due to its potential for movement with moisture changes.

• Engineered Fill Soil: Engineered fill is chosen and processed to replace poor-quality native soil, providing a stable foundation for structures. Its suitability depends on the engineering design and proper implementation for the specific project.
• Dumped Fills: Due to their low gravel content and good drainage, variable loamy and silty soil mixtures are often used as landfill cover. Dump fill can be re-engineered for foundation use, but this requires careful assessment and improvement to ensure proper strength, compaction, and consistency for safety.
• Hydraulic Fills: These are typically dredged from waterways and used to raise land levels or create new land. They may also contain organic materials or undesirable components. Careful assessment is crucial before using hydraulic fills for construction, as they are not native soil.

• Coarse-Grained Soil: This mixture of sand, gravel, and other fine materials is an effective backfill due to its low plasticity and good drainage properties. When adequately compacted, coarse-grained soil provides a stable foundation for many construction projects.
• Fine Graded Soil: Fine-grained soils include silt, sand, and some clays. Silt and sand with low-to-medium plasticity have good drainage properties and make good backfill. High-plasticity clays aren’t recommended as backfill due to shrinking and swelling issues. Proper compaction is essential for all backfill.
• Commercial By-Products: Lightweight materials like furnace slag or fly ash can be used as backfill additives or for specific situations like constructing high walls. Their backfill suitability depends on the product and desired backfill characteristics.

Native soil is the natural soil on the construction site. It can be used unmodified or modified with sand, compost, or porous ceramic soils to improve construction suitability. Whether to use native soil depends on soil conditions, weather patterns, and site usage frequency. Native soil is generally a more cost-effective option compared to imported backfill materials.

• Excess Moisture: Saturated soil loses bearing capacity, potentially causing foundation settlement. This is especially true for clay soils that expand significantly when wet. Drainage system installation helps drain excess moisture before it accumulates and causes damage.
• Freeze-thaw Cycles: Repeated soil freezing and thawing can cause foundation heave and movement. As water in the soil freezes, it expands, pressuring the foundation and causing cracks and lifting.
• Drought: Extreme dryness shrinks some clay soils, leading to foundation cracks as the soil pulls away from the structure.
• Soil Erosion: Erosion removes soil around the foundation, exposing the area to the elements and weakening its support structure. In severe cases, this leads to settlement, cracks, and foundation failure. Builders have various methods to prevent soil erosion from compromising foundations. These include implementing slope stabilization techniques and employing proper landscaping practices.

• Misaligned doors and windows
• Brick cracks
• Floors cracks
• Uneven floors

• Drywall cracks and nail pops
• Floor gaps
• Cracked chimney
• Collapsing retaining wall

• Push Piers: Push piers are driven deep into the ground until they reach stable soil layers. They are an excellent solution for stabilizing and potentially lifting a foundation, addressing issues caused by unreliable soil.
• Helical Piers: Helical piers are rotated into the ground to provide robust foundation support. They address existing foundation problems by lifting or stabilizing the structure and preventing future issues caused by poor soil conditions.
• Slab Piers: Slab piers address concrete foundation settlement. They transfer the structure’s weight from unstable to stable soil layers, providing a solid foundation.

Understanding soil types and their impact on your home is crucial for long-term foundation stability. Proper drainage, recognizing settlement signs, and considering repair options like foundation piers are essential. For a free inspection and expert advice, contact JES Foundation Repair to address your foundation concerns. We proudly serve Virginia, DC, Maryland, North Carolina, and surrounding areas.