The health of a foundation can depend on the type of soil it sits on. Different soil types have different properties, which makes them either suitable or unsuitable for certain construction work. If you are wondering what the difference is between a man-moved and backfill soil, or what the traits of native soil layers are, keep reading. We will take a closer look at these three soil types and what we can expect from them.
Your whole home sits on your foundation, so this element plays a key part in maintaining the structural stability of your house. Because of this, every aspect of the foundation construction needs to be carefully calculated. From the building process to the choice of materials, everything has to be by the book, otherwise, the foundation won’t be able to bear the load. One factor that mustn’t be overlooked is the soil that supports the foundation. It needs to be stable so it can properly support the load above. Not all soils are the same, and some do not have the qualities needed to support a building. Constructing a foundation on unstable soils can lead to cracks, settling, and seriously compromise the structural stability of the house. Here are different types of soils and their physical properties.
Any soil that has been excavated in one location and then moved to another for construction is called man-moved soil. As the population in urban areas is increasing and cities are expanding, some areas that should be developed simply lack good soil. In this case, there is massive excavation, the dugout soil is relocated someplace else and replaced with quality soil. There are three types of man-moved soil.
- Engineered fill soil: This type of soil is used on construction sites and its purpose is to replace non-engineered soils. With engineered fill, builders can get good soil that will support structures and build in places where that wasn’t possible before. This type of soil consists of subgrade soils or granular materials and can properly support many foundations.
- Dumped fills: This soil is used to cover the landfills and has less gravel and stones. It can also be re-engineered and used to create a foundation.
- Hydraulic fills: This type of soil is used to raise the level of land and originates from water bodies. This is a multi-layered soil and contains organic and deleterious materials. This soil can in some cases be used as native soil.
When the foundation is created, the soil where the structure will be needs to be excavated. After the foundation is complete, a part of the excavated soil is put back to fill the gaps between the foundation and earth. This restores the soil’s stability. This type of soil that is excavated and then put back in the ground is called the backfill soil. There are three variations of backfill soil.
- Coarse-grained soil: This type of soil has low plasticity and is a mixture of sand, gravel, and some fine materials. This soil is compact, which makes it suitable for foundation support.
- Fine-graded soil: If soil contains particles smaller than 0.075 mm it is called fine-graded soil. The most common kinds of fine-graded soil are sand, silt, and some clay soils. These have low-to-medium plasticity and can be used as backfill soils. When they are compacted with heavy machinery, they can properly support the foundation.
- Commercial by-products: Lightweight by-products such as furnace slag are sold as backfilling materials. When the soil has high plasticity, these by-products are used to turn them into suitable materials for backfilling.
Native Soil Layers
These soils are from their true native field and have not been disturbed in any way. When builders use native soil layers, it means they use only the soil available on site. If by some chance native soil layers are not that stable, they can be modified with peat, sand, compost, or porous ceramic soils. Whether builders will use native soil or not depends on the condition of the soil, the weather, and how often the site is in use.
Other Soil Sub-Categories
Other types of soil can be used in construction.
- Clay Soil: This common type of soil has one major flaw. It shrinks when it is dry and expands when it comes in contact with water. This is why clay soil is not a suitable building material. A foundation built on such soil tends to crack and settle.
- Rock Soil: Rock soil doesn’t react in any way when it is exposed to moisture, which is what makes it the perfect construction material.
- Sandy Soil: Although sand, unlike clay, doesn’t shrink or swell, it can erode over time, which can be a problem. Proper drainage needs to be established to prevent erosion.
- Loam Soil: Loam soil consists of sand and silt and holds moisture very well. Its draining properties are also good. However, due to having sand in it, it is prone to erosion and does not provide proper support to the foundation.
- Shale: This is a type of sedimentary rock that contains quartz, clay, and other minerals. It falls into the category of rocks known as mudstones. Due to the clay in it, shale can shrink and swell depending on the moisture levels.
If your home wasn’t built on stable soil, your foundation could be in danger. In case you have noticed settlement signs such as cracks and uneven floors, contact professional contractors at FSM and schedule a free inspection and repair estimate. Our inspector will assess the situation and recommend solutions suitable for your home.