What Does Underpin Mean In Construction?

What Does Underpin Mean In Construction?

What Does Underpin Mean In Construction?

In construction, underpinning is a technique used to strengthen or support an existing foundation or structure.

It involves digging around and under the existing structure, inserting several supports underneath the current foundation and then gradually strengthening them over time.

This process helps to increase the stability of the structure by reducing movement from wind and vibration, as well as providing additional protection against shifting ground conditions.

Underpinning is commonly used for foundations that have settled due to poor design/construction methods or when loading conditions have changed significantly since the original construction was completed.

What Are Some Examples Of Underpinning?

When it comes to foundation repair, underpinning is an essential part of the process. Underpinning is a method of strengthening existing foundations and supporting existing structures, offering multiple solutions for home and business owners.

In this blog post we will explore different types of underpinning activities and provide examples for each one.

The main categories that we will be looking at are helical pile underpinning, push pile underpinning, drilled concrete underpinning (caissons), mass pit concrete underpinning and mini pile underpinning.

In this blog post, we will explore what underpinning is and provide some examples of how it can be applied in different settings.

  1. Helical Pile Underpinning

Helical pile underpinning is a soil stabilization technique used to strengthen foundation support, often in situations where the existing foundation needs extra support.

This method uses helical piles, which are steel shafts with circular plates at their base, to vertically stabilize and resist tilt of the foundation structure.

Helical piles can be driven into most types of soil and are commonly used for remediation projects when the existing foundation is not strong enough or needs to be extended.

The technique can also be used to prevent further deterioration of an existing foundation caused by soil erosion or seismic activity.

  1. Push Pile Underpinning.

Push Pile Underpinning is a technique used to provide extra support for foundations in areas where the soil is weak and unstable.

It involves placing large, heavy piles of concrete or steel underneath a foundation to bear more weight and distribute it over a larger area.

This helps prevent any movement of the foundation, making it less likely to be affected by vibrations, moisture variations, frozen ground pressure, and other environmental factors.

Push pile underpinning also increases the overall stability of a structure, allowing for larger buildings or higher construction in weaker soils.

  1. Drilled Concrete Underpinning (Caissons)

Drilled concrete underpinning, also known as caissons, is a type of underpinning that is typically employed on more severe cases of structure settlement.

This process involves the drilling of large-diameter shafts below the existing foundation and filling them with concrete to help support the settling structure and prevent further damage from occurring.

This method works well for encroaching soil conditions or other unstable supporting soils, providing for greater uniformity in bearing capacity and load distribution than mudjacking or slabjacking.

It’s important to note that drilled concrete underpinning should only be used by professionals because it requires specialized tools and experience to ensure proper installation and minimize potential risks associated with this type of repair.

  1. Mass Pit Concrete Underpinning.

Mass pit concrete underpinning is a type of underpinning that can be used to deepen, strengthen and stabilize the foundation of a building.

This method involves excavating huge pits, which are then filled with concrete reinforced with rebar. This helps stabilize the existing structure and provides additional strength and support.

The bottom part of the pit may also contain extra concrete or steel reinforcement for added stability.

This is often an effective solution for stabilizing problematic foundations, however this process may be costly depending on the size and complexity of the project.

  1. Mini Pile Underpinning

Mini pile underpinning is a type of underpinning that is used in situations where conditions are too shallow to use traditional underpinning.

It involves first driving small capacity piles into the ground and then grouting the spaces between them so that they form a strong supportive foundation layer.

This method works well for projects that involve limited space, as it requires minimal excavation and can be used on smaller building foundations. Mini pile underpinning is an economical solution for many residential building projects.

What Are The Reasons For Underpinning?

Underpinning is the process of strengthening and consolidating the foundation of an existing building or structure by adding additional materials underneath.

The main reasons for underpinning a structure are to strengthen it against subsidence and sinkage, repair damage caused by ground movement such as seismic activity or vibrations from adjacent construction projects, increase the load-bearing capacity of existing foundations, allow a building to be extended downwards in height, anchor a structure into more stable soil strata, add additional foundations when there is limited space above ground level, change the structural layout within a building, provide support for side fill operations such as vibratory compaction or ensure that any alterations meet current building regulations.

What Are The Stages Of Underpinning?

The process of underpinning consists of five stages: excavation, shoring and bracing, filling with concrete, forming and finishing.

  • Excavation involves digging a trench that is deeper than the old foundation and wide enough to accommodate the new foundation wall.
  • Shoring and bracing involve installing supports along the sides of the trench to prevent its collapse while the concrete sets.
  • Filling with concrete involves pouring a mixture of cement, sand, gravel and water into the trench to form a solid base for building upon.
  • Forming involves constructing additional walls within the trenches to support whatever is being built upon it.
  • Finally finishing entails troweling on a layer of mortar or bituminous material over the newly formed wall in order to waterproof it as well as any surface level aesthetic changes that may be desired.

What Are The Risks Of Underpinning?

Underpinning is a process where additional structural support is added to an existing foundation to prevent further deterioration or provide additional strength.

This type of work requires a highly trained professional with extensive experience in the building industry due to the risks associated with it.

It can cause problems such as altering the load-bearing capabilities of existing supports and foundations, resulting in collapse of walls, slabs or other overhead structures.

Furthermore, it could also create further damage to adjacent buildings or systems connected to them (such as plumbing).

Lastly, if done incorrectly, it might lead to structural failure and dangerous conditions for workers involved in the underpinning process. Thus, the importance of thoroughly assessing all potential risks before committing to any project cannot be understated.

What Is Minimum Depth Of Underpinning?

Underpinning is a structural repair process used to reinforce the foundation of an existing building or structure.

It involves excavating and installing additional concrete deep below the level of the existing foundation in order to provide stability and additional support.

The minimum depth of underpinning depends on several factors such as soil type, foundation type and the amount of load that must be supported.

Generally speaking, underpinnings should extend at least two feet below the bottom of the existing foundation, but it can extend deeper if necessary.

In addition, any support piles must also be long enough to bear their own weight plus any additional load that needs to be supported by them.

What Is The Difference Between Underpinning And Piling?

Underpinning and piling are both methods used to support or stabilize a structure, often when the existing soil is unable to provide adequate stability.

The main difference between underpinning and piling is that underpinning involves digging out and replacing the existing soil beneath a structure, while piles are driven deep into the ground, either through impact or with a drilling machine.

Underpinning is suited for buildings with shallow foundations, while piling is better for deeper foundations where higher loads need to be supported.

Piling also provides greater flexibility when dealing with difficult ground conditions such as variable soils or large water tables.

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