Foundations are the first building block of a stable structure, and there are many diverse types of foundations that builders use. The selection of the type of foundation depends on a variety of factors.
These factors include the type of structure being built, the variety of soil where the building is located, and the various loads that the building will bear over time. There are straightforward, simple types of foundations like strip foundations as well as intricate types like caisson foundations.
Each foundation type is tailored to meet specific goals and the unique demands of the project. Knowledge of all the advantages and disadvantages of each type is essential for building professionals and avid DIYers.
Primary Types of Foundations
There are two main categories that include all the types of foundations: shallow foundations and deep foundations. These categories are named for the depth in which builders place the foundation elements.
1. Shallow Foundations
Builders install shallow building foundations close to the ground surface. They use this type of foundation when they can locate stable soil layers within a short depth. Shallow foundations are popular for small building structures and houses.
Shallow foundations have many advantages including cost-effectiveness, speed of construction, and minimal soil disturbances. Yet shallow foundations are limited because of their limited load-bearing capacity and their susceptibility to severe weather conditions. Some common types of shallow foundations are strip foundations, pad foundations, and raft foundations.
2. Deep Foundations
Builders use deep foundations when they cannot find stable soil layers close to the ground surface or if they are building a building that bears heavy loads. Builders extend this type of foundation deep into the ground so that they can transfer the load of the building to stable soil or rock layers.
Common advantages cited for deep foundations include a high load-bearing capacity, suitability for different soil types, and reduced risk of settlement. Builders must weigh these benefits with the higher cost of deep foundations, extended building time, and greater environmental impact. Common types of deep foundations include pile foundations, caisson foundations, and pier foundations.
Shallow Foundation Types
Builders use shallow foundations when they can find stable soil close to the surface of the ground and for small buildings and residential properties. Engineers regard foundations as shallow if their width is less than their depth.
Strip Foundations
Strip foundations, also called spread footings, consist of continuous strips of concrete or masonry that run below load-bearing walls or columns. This type of foundation distributes the load of the building across a wide area, reducing the pressure on the ground below. This is a common foundation type for small buildings and homes.
Pros
- Uniform load distribution – Spreads the load of the building evenly across the ground area
- Cost-effective – Less expensive to construct than other complex forms
- Suitable for uniform soil – Suitable for uniform, stable soil conditions with moderate load buildings
Cons
- Limited load capacity – Not suitable for buildings with heavy loads or significant weight
- Settlement risk – Susceptible to differential settlement, risking an uneven foundation.
Pad Foundations
Pad foundations, also called isolated footings, are individual concrete pads that builders construct under each column or pillar of a structure. These footings transfer the concentrated load from the pillar to the soil below. This foundation type is suitable for small structures or for buildings where the load is clearly defined.
Pros
- Focused load distribution – Ideal for structures with individual columns or pillars to more evenly distribute the load.
- Versatile – Builders can adapt for buildings with any configuration of columns
Cons
- Limited load distribution – Not efficient for spreading the load over a large area, making this an unsuitable type for large structures
- Settlement risk – Can experience differential settlement leading to an uneven foundation
Raft Foundations
Raft foundations, or mat foundations, consist of large horizontal slabs that cover the entire building footprint. These mats, or slabs, help to distribute the weight of the building over the underlying area which reduces the pressure on the soil below. Raft foundations are beneficial when the soil below the building has an uneven quality.
Pros
- Uniform load distribution – Distributes the load evenly across the foundation, reducing the risk of differential settlement
- Stability – Suitable for soils with uneven load-bearing capacity because it distributes the load across the foundation
Cons
- Complex design – Requires careful engineering and planning, leading to a higher cost
- Site preparation – May need extensive excavation to prepare the site, creating a longer timeline and higher costs
Slab-on-Grade Foundations
Slab-on-grade foundations, also monolithic slab foundations, are simple, single-layer concrete slabs that builders pour on the ground surface. This is a common foundation type for simple residential constructions. It is not suitable for heavy loads or structures with many stories.
Pros
- Simple construction – Easy and quick to construct, which makes it suitable for residential properties
- Thermal benefits – Thick concrete slab provides insulation from the cold to the upper level
Cons
- Limited load capacity – Not suitable for buildings with heavy vertical loads
- Vulnerable to settlement – Prone to cracking and settling if not designed or built well
Frost-Protected Foundations
Builders construct frost-protected foundations in climates that are prone to freezing temperatures. They incorporate insulation around the foundation’s perimeter to prevent freeze-thaw cycles in the soil beneath the building foundation. This insulation helps to reduce the movement of the soil and minimize the risk of cracking in the foundation.
Pros
- Frost prevention – Engineers designed this type specifically for climates with hard winters to mitigate the damage of frost to foundations
- Saves energy – Incorporates extra insulation so it adds greater energy efficiency in the upper structure
Cons
- Specialized design – Requires specialized materials and construction, so it requires greater complexity and cost
- Site-specific – Relevant in cold climates, but limited applicability elsewhere
Deep Foundation Types
Deep foundations carry a greater cost because of their complex design and specialized materials. Yet these are the only foundation type that is suitable for heavy-load commercial buildings or other complex structures.
Pile Foundations
Pile foundations require driving or installing cylindrical or prismatic elements, piles, deep down into the ground until they reach stable soil or a bedrock level. Manufacturers construct piles out of concrete, steel, or wood. These piles help to transfer the load of the building to the surrounding soil through friction and through the end to the stable ground surface below.
Pros
- High load capacity – Ideal for bearing heavy vertical loads, making them an appropriate choice for tall buildings and heavy structures
- Versatility – Builders can use many types of piles and different arrangements to craft a foundation suitable for their project
- Suitable for challenging soils – Appropriate for weak or unstable soil conditions where a shallow foundation type would not work
Cons
- Complex design and installation – Requires complex engineering and specialized equipment to design and install, which can increase cost and timeline
- Environmental impact – Installation process creates deep earth vibrations and noise that will affect the surrounding environment
- Limited access – Installation requires a wide scope which means that this foundation will not work in areas with limited space
Caisson Foundations
Caisson foundations require excavation of the soil below the structure and inserting a large-diameter cylindrical structure into the space. This structure can have an open caisson, which features an open bottom. This opening allows water and soil to flow in. A closed caisson is filled with concrete to create a water-tight foundation.
Pros
- Suitable for waterlogged areas – Common foundation type in areas with a high water table as builders can install them while keeping water out
- Stability – Provide stability and load-bearing capacity in unstable soil or soil with a high water content
- Deep penetration – Can reach significant depth, making this type appropriate for buildings that need heavy structural support
Cons
- Complex construction – Installation of caissons requires extensive planning and specialized equipment, increasing cost and construction time
- Engineering expertise – Proper design and construction is crucial to the success of caisson foundation, ensuring that they are durable and can withstand heavy loads
Pier Foundations
There are two broad types of pier foundations, masonry and drilled shafts. Masonry piers are a shallow foundation type that consists of vertical columns made of masonry materials like bricks, concrete blocks, or stones. These columns transfer the load from the structure to the ground. Masonry piers are only suitable for light structures as they do not extend far into the ground.
Builders construct drilled shafts or drilled caisson foundations by drilling holes into the ground and filling them with concrete. These foundation piers extend deep into the soil to reach stable soil or a bedrock level. Engineers consider these a deep foundation, so they are suitable for heavy structures.
Pros
- Load distribution – Well-suited for structures with concentrated loads as they transfer the burden from the structure to the ground below
- Versatility – Adaptable foundation type for different soil types and weight of buildings
- Site adaptability – Appropriate foundation type for uneven terrain
Cons
- Specialized design – Careful design and planning are necessary to choose pier type, spacing, and size
- Susceptibility to moisture – Susceptible to moisture, which can cause deterioration if the piers are not sealed
- Lateral stability – Piers may need more lateral support if they are exposed and face extreme winds or seismic events
How to Choose a Foundation Types
Choosing a foundation type is a complex process that requires a systematic consideration of your building needs, soil type, budget constraints, and skills needed.
- Site and Soil Considerations– Assess the site for your building including the topography and the soil conditions. This will help you determine the soil’s load bearing capacity, potential for settling, and the groundwater level.
- Project Type and Style – Consider the type of building you want to create, its size, load-bearing capacity, height, and footprint. The larger structure you create, the more extensive the foundation planning should be. Foundation types also affect the look of the building, which may influence your choice.
- Budget and Timeline – Complex foundation types carry a higher cost and a longer timeline. Consider a more simple foundation type if you are facing time and budget constraints if the structure you are creating allows for this.
- Local Building Codes and Safety Considerations – Study your local building codes to see which type of foundation they require for specific building types. This will ensure that you build the proper foundation with the highest level of safety.
- Expert Consultants – Consider the advice of experts in the field like engineers and experienced builders. Even if you are doing the work yourself, it can help to get their input before you begin your project.
The post Pros and Cons of Types of Foundations for Houses and Buildings appeared first on Homedit.
0 Commentaires