What is Pier Beam Foundation
A pier foundation is a collection of large diameter cylindrical columns that support the superstructure and transfer large super-exposed loads to the bottom firm layer.
It stood several feet above the ground, also known as the “Post Foundation”.
Types of Pier Foundation:
There are 2 Types of Pier Foundation
- Masonry or concrete pier
- Drilled caisson
1. Masonry or Concrete Piers
Masonry or concrete piers depend on the level of the stratum. If a good bearing layer is present up to 5 m, masonry piers are used. The size and shape of the pier depending on the nature of the soil, depth of the bed, etc.
The concrete pier is made of concrete. These are precast, as well as cast in situ piers, precast concrete piers, built into a factor and then driven into the ground at the required location. The precast concrete pier is usually reinforced with steel wires.
When a good bearing layer protrudes 5 m below ground level, brick masonry or concrete foundation piers can be used in the excavated pits.
The precast concrete pier is usually reinforced with steel wires typically 30 cm to 50 cm in cross-section and 20 m in length and a cast steel pier is provided at the bottom of the pier.
2. Drilled Caissons
Drilled caissons usually refer to cylindrical foundations. A drilled caisson is roughly a compressed member subjected to an axial load at the top and a reaction at the bottom.
Drilled caissons are usually drilled by mechanical means. Drilled Cassians are three types
- Concrete caisson with enlarged bottom
- Caisson of steel pipe with concrete filled in the pipe
- Caissons with concrete and steel core in the steel pipe
Pier Foundation Construction Details:
Pier Foundation Spacing
The spacing of the pier is usually built 1-1.5 feet above the ground. This gap (how far apart the pillars of the foundation are) is necessary to prevent moisture from damaging the wooden structure.
Shape and Size of piers
Piers can be made from a variety of materials
- Wood
- Brick
- Solid concrete
The shape of the piers is:
- Square
- Rectangular
- Circle
The diameter of the piers is usually 6 inches, 8 inches, 10 inches, 16 inches. The depth of the pier foundation is below the depth of freezing. The depth is about 5-6 feet.
Materials Used in Piers
Wood, brick, concrete, etc. are used in the piers. But the most commonly used material is reinforced concrete. It provides the highest compressive strength and has a high tolerance to tensile stress. In addition, reinforced monolithic columns can withstand any type of frost and will not crack under these forces. And it is quite easy to dilute the concrete mix and pour it into the holes.
Pier Foundation For Shed
- A shed pier foundation is not a strictly permanent foundation. It consists of a series of concrete blocks placed directly on the ground (sometimes a shallow hole is dug and filled with crushed stone), then the top of the block is placed on top of the main floor. To support is layered beams of the shed.
- We need 6 piers, 3 per long side for 8 ft x 12 ft shed
Pier Foundation Repair
Some Remedies For Repair Pier Foundation
- Reshimming
- Rebuilding or Adding Pier Stacks
- Replacing Wood
- Adding Underpinning to the Beam
Types of cross-section
There are several types of cross-sections of foundation pillars. It can be cylindrical, helical or box-shaped, or a more complex form in which the lower part of the posts can be widened. Widening can increase the area of the base and thus increase the load-bearing capacity of the foundation. The weight of the house will be distributed over a large area.
Grillage in Pier Foundation
The top of the pier foundation that joins the different posts into a single structure is called the grillage. When heavy structural loads from columns, piers, or stanchions need to be transferred to soils with low bearing capacity, grillage foundations are used. Grillage is often found to be lighter and more economical.
Advantages of Pier Foundation
- This method is easy and requires less amount of material and labor. The required material is easily available.
- There is a wide range of variety when it comes to design. Here we can use different materials to enhance the beauty scene and it stays within our budget too.
- Pier foundation saves money and time because it does not require extensive digging and a lot of concrete
- It causes minimal disruption to the soil environment. A shovel can be used for digging and the existing roots and soil organisms remain mostly undisturbed. At the end of the building’s useful life, it will be easier to restore the site to its natural state than a site with a full basement.
- Since it elevates the house above the ground, a flood cannot cause any damage to the structures.
- The space between the house and the ground is large enough to install utilities such as plumbing and electrical wiring.
- Workers can easily get under the space between the house and the ground as there is enough room to crawl to solve plumbing and electrical related issues
- It is comfortable to walk on a floor that does not rest on a hard surface and is good for people with arthritis and back pain
- inspection is possible because the shaft diameter is large
- In the case of drilled pier construction, the ground vibration that is usually associated with driven piles is absent.
- The bearing capacity can be increased by reducing the bottom (in non-caving materials).
Disadvantages of Pier Foundation
- This type of foundation tends to get wet in the crawl space. Therefore necessary steps must be taken to remove any water from the crawl area.
- Creeping places in this type of foundation can be attractive for insects and other animals to live in. To control this problem a screen should be installed over the opening.
- In the winter months when cold air enters due to crawling, the whole house becomes cold.
- Houses on foundation poles may shake from their foundations in earthquake-prone areas.
Difference Between Pier Vs Pile Foundation:
- Pile foundation transfer load through friction and bearing and pier foundation transfer load through bearing only.
- It is preferred in a location where the top level consists of disintegrating rocks above sound rocks, the difference between a cast-in-situ pile and a pier is arbitrary, a cast-in-situ pile in diameter is greater than 0.6 m.
- The difference between pile foundation and pier foundation is in the method of construction. Although pile foundations transfer loads through friction and bearing, pier foundations transfer loads only through bearings.
- Typically, pier foundations are shallower than pile foundations. Pier foundation is preferred over the place where the top-level has decomposed rock above the sound rocks. In such a situation it becomes difficult to drive effective piles through decomposed rock.
- In the case of hard soils, which offer great resistance to the driving of a bearing pile, a pier foundation can be easily erected.
- A pile is a vertical column of a relatively larger cross-section than a pile, installed in a dry area by digging a large diameter cylindrical hole to the desired depth and backfilling it with concrete.