Which is better – strip foundation or screw piles?

A building’s stability and lifespan are affected by the choice made during construction between screw piles and a strip foundation. Each approach has advantages and disadvantages depending on the kind of soil and the needs of the building.

A strip foundation, sometimes referred to as a continuous footing, is a conventional technique in which a concrete strip is placed beneath a building’s load-bearing walls. By equally distributing the weight across the soil, it creates stability and deters settlement. In regions with steady soil conditions and moderate building loads, this kind of foundation is typical.

Contrarily, screw piles are made of helical-bladed, cylindrical steel rods that are screwed into the ground. They depend on the soil’s bearing ability to sustain the structure above. In regions where conventional foundations might be less successful due to challenging soil conditions, such as soft or sandy soils, screw piles are beneficial. They provide easy installation with little disruption to the neighborhood.

The decision between screw piles and strip foundations is frequently influenced by variables such as building size, type of soil, and environmental concerns. Because they offer a stable base for the majority of buildings and are dependable and appropriate in typical soil conditions, strip foundations are preferred. Their careful excavation and concrete pouring requirements can cause delays in construction schedules.

Conversely, screw piles are becoming more and more common because of how simple and adaptable they are to install. They are perfect for projects that need quick fixes for the foundation or where traditional methods are not practical because they can be installed without requiring a lot of excavation in a variety of soil conditions.

In conclusion, a careful evaluation of the soil conditions, project requirements, and financial concerns should be the basis for choosing between screw piles and strip foundations. Depending on the situation, each approach has a unique set of benefits that guarantee a strong foundation and the building’s long-term integrity.

Strip Foundation	Screw Piles
More traditional and widely used in construction.	Effective in areas with unstable soil or where fast installation is needed.
Requires extensive excavation and concrete work.	Minimal ground disturbance during installation.
Suitable for heavier structures needing a stable base.	Can be installed in areas with limited access or space.
Longer construction time due to curing of concrete.	Quick installation reduces overall construction time.

Description of foundations on piles

Strong pillars that are driven, screwed, or inserted into the ground and rest on compacted soil layers below freezing temperature are the intended function of piles. A horizontal grillage at the top connects each pillar head to the others, distributing the weight load from the walls equally amongst them.

The installation and execution methods of three primary types of piles are distinguishing factors:

• clogging;
• screw;
• Buronaby.

They are composed of:

• wood trunks;
• metal rolling;
• not reinforced concrete;
• reinforced concrete of factory molding.

It is important to note that wooden pile supports are now incredibly uncommon and are only utilized for short-term constructions, the lifespan of which is no longer than two to three years.

Chopped heaps. These kinds of supports are created in a factory using reinforced concrete and are scored in the ground with specialized construction tools (you can read more about the topic here). The construction of massive, private buildings and multi-story buildings both use the technology known as "clogging piles."

Usually, a shallow foundation is used as a grillage. Although driven-in reinforced concrete supports are very reliable, they are also the most expensive due to the high cost of materials and the need for specialized equipment.

Screw arrangements. formed from pipes of rolled steel. They consist of a pointed-ended steel pipe structure with screw blades welded above. All types of soil can be supported by screws; the only exceptions are high-stone and swampy peat bogs.

Able to be put in either mechanically or manually. Grillage is made of rolled steel in the shape of profiled pipes, I-beams, or channels. Installing a shallow tape grillage or one made of reinforced concrete is permitted.

Bored supports. This kind of pile foundation is installed by digging wells to the depth of soil freezing with a calculated diameter. They are then filled with a cushion of crushed stone mixed with sand, and hollow formwork composed of pipes or rolled sheet material is installed. Concrete mixture is poured into the structure after a reinforcing frame is installed inside. The top portion of the supports are connected by a concrete grillage once the concrete has hardened.

In private construction, bored supports are frequently utilized for the construction of one- and two-story stone buildings because of their higher load-bearing capacity. Any kind of soil can be used for construction thanks to excellent structural stability.

Description of strip foundations

These are enormous constructions composed of brick, stone, or reinforced concrete. Such a foundation is a continuous, flat-striped wall support in terms of its external configuration. The process of building a strip foundation is costly and labor-intensive due to the extensive material usage.

The stone belt bears the full weight of the building’s structural loads, which are then dispersed equally across the ground.

It can be used for any building up to five stories high on stable, dense soils. The house can only be two stories tall in cases of heaving, weak soil, and horizontal movements.

Use caution when applying on clayey and marshy soils.

Large-scale excavation work must be planned and executed in order to install a strip foundation. Nevertheless, these efforts will be worthwhile if you have a large cellar or basements. In contrast to pile foundations, the tape requires formwork, the installation of reinforcing frames, and the installation of a cushion made of crushed stone.

Advantages and disadvantages of pile foundations

The benefits and drawbacks of pile supports must first be identified in order to set up a basis for comparison regarding the superiority of screw piles over strip foundations. Advantages:

• the cost is 25-30% lower than that of strip structures;
• fast construction time of the supporting structure;
• possibility of construction on most types of soil;
• high level of stability and durability;
• lack of excavation and use of bulk non-metallic materials;
• performing work at any time of the year, even at sub-zero temperatures;
• ability to withstand heavy weight loads.

Although pile foundations have many advantages, they also have some drawbacks. These include:

• impossibility of installing piles in rocky and rocky soils;
• lack of basements under the building on a pile foundation;
• the need to insulate the free space under the floor when installing a basement wall.

You can select and purchase low-quality material if you are unaware of the specifications needed to manufacture piles. For instance, metal screw products that are designed improperly for your type of soil, have thin pipe walls, or have poorly welded blades. It is therefore preferable to trust a professional to handle the material purchase and installation.

Pros and cons of strip foundations

The ability to arrange basements and provide the lower portion of the building with high-quality insulation is the primary benefit of a strip foundation. Utility lines can be installed, a non-freezing water supply can be established, and multiple utility rooms can be set up in the basement or ground floor.

Even with the substantial amounts of excavation and installation work, building a strip foundation can be completed alone with the help of two to three assistants. For concrete compaction, you only need a vibrating device and a concrete mixer among special construction equipment. You can just hire an excavator to dig a pit.

A well-constructed strip foundation is resilient and can endure for 150 years, even in the face of adverse environmental factors. The structure will be shielded from groundwater and melt water by a layer of hydraulic insulation, and heat loss will be decreased by thermal insulation.

However, despite all of the benefits mentioned, tape-type bases have a few major drawbacks, including:

• large labor costs during the execution of work at all stages;
• a long construction process associated with large volumes of excavation work and concrete hardening time (we described the technology here);
• high construction costs;
• impossibility of construction on certain types of soil;
• the need for process continuity when pouring concrete.

However, if we consider the developer’s reviews, the high degree of structural reliability and the existence of a basement completely justify the listed shortcomings.

Comparison of two foundations

Which type of foundation works better, pile-screw or strip? Since strip foundations are a traditional building method that has proven effective for many years, they are actually utilized in the construction of buildings.

Practice, however, demonstrates that pile supports are more capable of supporting a larger weight. Let’s attempt to compare these two designs using the following metrics:

• financial expenses;
• construction time and labor costs during construction;
• possibility of application;
• technological effectiveness and seasonality.

Financial expenses

Strip or pile foundations—which is less expensive? There are expenses associated with building a strip foundation that are not necessary for pile structures:

• excavation and leveling, storage and removal;
• transportation costs for the delivery of equipment, reinforcement and concrete mixture;
• backfilling the sand and gravel cushion and compacting it;
• concreting or installing blocks using lifting equipment.

Strip foundation costs significantly more overall.

Construction time and labor costs

A strip foundation’s structure is far more intricately designed. It will require time to excavate, install formwork and a reinforcement cage, install an underlying cushion, and pour concrete during construction. After that, you’ll need to wait for the concrete mixture to properly set before starting any waterproofing projects.

It suffices to screw, drive, or install piles in a pile foundation, then tie them together with grillage. The task is finished many times more quickly.

Possibility of use

Depending on the type of soil, there are essentially no limitations on the use of pile foundations. The one exception are marshy peatlands, where construction is typically nonexistent. However, the depth at which a strip foundation is laid determines its application.

Only lateral loads act on the strip when the structure’s sole is supported by dense soil layers that are below freezing, and the stability of the strip is determined by the degree of reinforcement—that is, the strength of the reinforced concrete. Only stable, dense soil with deep groundwater and a shallow freezing depth is suitable for the use of shallow foundations.

The cost of a strip foundation increases significantly in complex terrain with slopes or elevation changes, but a pile foundation solves the problem without any issues.

There are a few considerations to weigh when choosing between screw piles and a strip foundation for your construction project. A classic option, strip foundations are made up of an uninterrupted concrete strip and are renowned for their stability and capacity to equally distribute the weight of the building. They work best for structures on stable soil when excavation is practical.

Conversely, screw piles are more adaptable, particularly in regions with difficult soil types like sand or clay. By utilizing rotational force to drive these piles deeply into the ground, a robust anchoring system that can support a variety of structures is created without requiring a lot of excavation.

Your unique site conditions and project requirements will play a major role in selecting the best type of foundation. A strip foundation might be a simpler and more affordable option if you’re building on stable soil with good load-bearing capacity and have access to excavation equipment. It offers a strong foundation for structures of all shapes and sizes.

On the other hand, screw piles are a dependable solution if your construction site has issues with soil, such as high water tables, soft clay, or sandy soil that shifts easily. They are perfect for projects where time and ground integrity are crucial factors because of their rapid installation and low site disturbance.

The choice between screw piles and strip foundations ultimately comes down to weighing considerations including long-term structural requirements, construction schedule, soil conditions, and budget. It is essential to seek advice from a qualified engineer or foundation specialist to make sure your decision will support your construction project’s long-term durability as well as its immediate needs.

The decision between screw piles and strip foundations for building projects ultimately comes down to the particular requirements and circumstances. Strip foundations provide strong support over a wide area and are a traditional and dependable option for heavier structures and stable soil. Screw piles, on the other hand, work well in difficult soil types like sand or clay and offer a rapid installation with little disturbance. The decision is greatly influenced by factors like the project timeline, budget, and site characteristics. Comprehending these distinctions facilitates builders in making an appropriate selection, guaranteeing a robust and long-lasting base customized to meet the specific requirements of every building project.

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