Is Building A House On Sand Good?

Building a house is often a daunting task. Apart from the considerable capital outlay required, there is also the decision about what materials would be best suited. Ultimately this decision requires some sound research to ensure that the foundation is strong enough to hold up your hard-earned investment. I have often been asked this question Is Building A House On Sand Good?

Sand cannot be compacted and, as such, will never be a solid piece of earth for a foundation. Although sand is one of the most used materials in construction, the fine aggregate of the particles is not suitable; by combining other materials, you can create a stronger foundation.

Perhaps you are looking to build your house on sand or would like to enquire about the effects. Let’s explore the adverse effects of building a house on sand and what steps you can take to ensure that you can create a solid foundation.

Why Is It Not Advisable To Build A House On Sand?

Whenever I face this question, it reminds me of a story from the Bible. The story of a man that once built his house on sand and the rains came down, the floods came, the winds blew, and the house eventually fell because the foundation was not strong enough.

In hindsight, this story is a perfect illustration of what would happen in the natural if you built a house on sand. There are many reasons why building a house on sand is not a good option. Below are some of those reasons.

Texture Of Sand

In construction, sand is by far one of the most significant materials that are used. More than 50 million tons of sand are used annually in construction. However, building a house on sand alone is not enough due to its texture.

The texture of sand determines the performance and the strength and stability to be used in construction. The texture of the sand differs from fine, medium, and course. Although you can use some sand in construction, the texture of others is not viable for this purpose.

Smooth particles of sand would offer less resistance than rough textures. Sand is readily mobilized; there are no binding forces, and the structure built on sand can easily collapse. Especially if there is moving water, then the sand is easily migrated.

Sea sand does not offer high tensile or compressive strength; hence it is not advisable. The fine rounded particles of sea sand cannot provide adequate resistance to the harsh elements of nature.

Salt Content Of Sea Sand

The salt content in sea sand tends to absorb the moisture found in the atmosphere resulting in dampness. The presence of chlorine in seawater infiltrates through the sea sand, which, if combined with materials like steel and iron, can reduce its carrying capacity, ultimately leading to corrosion. If you build a structure on sea sand, it will not be durable.

Poor Tensile Strength Of Sand

The foundation’s strength will be the determining factor in its longevity. The material’s resistance needs to be so strong that come earthquakes or cyclones, the materials used will be able to hold the building in place. The poor tensile strength of sand, mainly sea sand, is not a conducive material for building a house.

Other Reasons

Soil can expand, causing it to push against a foundation and weaken it; therefore, it is not an ideal support structure.
Sand particles can wash away over time, leaving gaps beneath the foundation.

The Different Types Of Soil And The Challenges

The first step is to identify what type of soil type you are considering building on and identify the possible challenges.

Sandy Soil

Free–draining soil
Can feel gritty
Less stable for excavations as it dries out rapidly.

Challenges

Sandy soil has natural shifting characteristics; any drainage will further increase these characteristics, making it challenging for you to build a house on this type of sand. Due to its free-draining granular nature, loose sand can pose foundation challenges as it requires densification control to provide satisfactory settlement and bearing for new houses.

The use of sandy soil can be problematic. Clean sands or sands with fewer fine particles can be prone to liquefaction when subjected to excitation such as vibrations or seismic forces. These seismic forces can cause liquefaction and thus increase pore pressure to a point where the sand becomes suspended, and the strength is compromised.

The suspended sand-in-water mixture behaves like a liquid, and any objects sink to a point where the object weight is equal to the importance of the sand-water liquid. Once the excitation stops and pore pressure dissipates, the sand becomes frictional again, and the settlement stops.

Clay

It has a lumpy and sticky consistency
Rock hard when dry
Poor drainage
Few air spaces

Challenges

Clay has poor drainage characteristics and, as such, can exhibit large settlements under load. The clay is likely to swell or shrink when there are changes in moisture content. Soil heave is also a big issue when dealing with clay, which can ultimately push the foundation and structure upwards.

Silt

Smooth and soapy to the touch
Mimics clay or soil
Retains moisture
The structure of the soil is fragile

Challenges

Silt tends to hold its water and is often difficult to drain.

Peat And Organics

There is a high organic content
Dark in colour
High in water content

Challenges

Easily waterlogged and acidic
Typically, problematic for construction.
Exhibits high compressibility characteristics
The strength of peat can be challenging to predict.

What Happens When You Build Your House On Sand?

Beneath the sand lies a more complex, more cohesive soil; by digging deeper, you can successfully discover the other soil types used to build a house. However, you will need to pay careful attention to vibration, which can not only cause damage to your property but also to the neighbours, as vibration can cause the sand to settle, leading to catastrophic results.

Why does A Coastal Home Need A Stronger Foundation?

The most crucial structural element of your beach house is the foundation. Without the structural component of a foundation, the house can fall apart. Typical foundations in other residential areas might be adequate, but this is sadly not the case for beach houses.

There are various dangers associated with building on sand. The harsher conditions of the environment demand a stronger foundation. There is a possibility that sea swells might gush up to the property causing the structure to collapse.

If you build a foundation on the sand, it can also be subject to scour and erosion; for this reason, there is a stricter building code for the construction of beach houses.

Guidelines When Building A House On Sand

Suppose you live in a coastal region and plan to build a home, although sea sand’s texture and tensile strength may not be a viable option in the building process. There is still hope; many owners of seaside properties have still managed to build their dream homes.

Here are some of the guidelines when building a home on sand.

There is a stringent set of building codes for building coastal homes. Further information on these codes can be obtained from a building contractor. It is best to consult with a reputable contractor knowledgeable about building a house on sand.

The building codes of coastal homes dictate the need for an open foundation with a minimum height requirement for the main deck. The height requirement is essential to help lift the home on stilts so that the water can flow safely beneath the house without causing any structural damage.

A beam that is improperly anchored can become dislodged in heavy storms. When this occurs, the result can be the tilting of the house, making it unsafe for habitation. Hence it is crucial that you consider the depth of the beams.

The setting and anchoring of the beams involve several different techniques outlined by an experienced building contractor. The second option is the introduction of supports deep into the sand to provide some structural stiffness. The friction of driving support deep into the sand will prevent it from moving.

Is It Possible To Build A House On A Sandy Slope?

Building on a sandy slope can pose a lot of challenges. The drifting of the sand could pose one of the main challenges. In the case of unstable sandy soils, you can use pilings for the foundation. Helical piling has become the piling of choice for these terrains.

These pilings are driven between 10 to 30 feet into the ground on average. They are either used to support the building directly or support the foundation of the building. You can also make use of 2 methods.

The “Cut And Fill Method”- Involves levelling out the soil by cutting out the ground for the foundation; it can mean adding or removing the soil depending on the extent of the slope or the structural plans.

To make the plot level for the building, you can bring in soil. Depending on the amount of soil brought in, it can be an expensive process.

Use Of Stilts – A crane can be brought in to lift the home onto supporting wood or steel columns. Stilts are more cost-effective in comparison to the cut and fill method.

The Challenges Of Building On A Sandy Slope

The two main challenges of building on a sandy slope are

The Slope Gradient – The gradient rating will determine how challenging it is to build on a site. If the gradient ratings are less than 10%, the incline is considered slight making it easy to build on. Ratings of 11-20% are considered moderate, while above 20% are considered steep.The prices start to go up as the gradient ratings increase substantially.

Upslope Or Slope – An upslope plot is considered more challenging than a downslope plot as these plots requires a substantial amount of cutting and blasting and the transportation of rocks and sand.

Is It Safe To Build A House On Sand?

You can consider it safe to build on sand if you create a foundation. The following are the safest foundation options to use on sand.

Piles That Work By Friction- You must first calculate the length of the piles. Then drive the piles into the ground until the friction is large enough.

Excavate- You can excavate unstable sands according to the structure’s weight.

Using a beam foundation that will tie the columns together while distributing the pressure of the sand. In this way, the sand will develop little pore pressure. Pore pressure is the pressure of the water inside the soil. Because it drains so well, the possibility of sinking soil is significantly reduced.

What Is the Best Sand On Which You Can Build A Home?

Loam- When building a house on sand, you want to ensure that the sand does not shift, shrink, or expand while having the ability to handle the presence of water. The only type of soil that proves to meet all the requirements while creating the ideal balance to support a foundation. Loam is the best soil on which you can build a home.

Bedrock – Impermeable to water runoff and it will not change shape or size even in the presence of water. Bedrock will not shift or slide or even move.

Chalk – A type of clay that has extremely fine particles, consisting of alkaline rocks such as limestone. Unlike most clay, this type of sand is ideal for building on as the soil will retain moisture and will not shrink or swell irrespective of the presence or absence of water.

Combination Of Sand And Bedrock – Sandy soil with a gritty texture combined with bedrock. It is suitable for building because it allows water to drain away without moving or shifting. To add stability to the soil, you can compact it with sand particles. The irregular shapes will provide the required strength.

Conclusion

Building a house on sand alone is not an ideal solution. However, incorporating sand with other materials will help create a stronger, more firm foundation. This foundation will hold up your investment for many foreseeable years.

References

Chrissie Smuts

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