1. What is a single nail?

Single foundation, also known as cup foundation, is one of the foundations used a lot in construction. It belongs to the shallow foundation used to support one or a cluster of columns standing close together. This type of foundation can withstand loads and support housing or electric poles and abutments very well because it can lie alone and travel with a variety of shapes such as squares, rectangles, or circles.

What is a single nail?

We can say that this type of foundation is relatively easy to construct. It is also the cheapest nail. Thus, helping investors save a lot of costs during the construction process.

  1. Features and structure of single foundation:

In terms of structure, the single foundation is quite simple. Single foundation can be divided into two types: brick foundation and reinforced concrete foundation. In particular, with the kind of brick foundation consisting of layers of bricks stacked on top of each other. Mainly, the type of reinforced concrete foundation with structure will be divided into two parts as follows:

  • Basement concrete layer:  It has a thickness of about 100mm, made up of 4×6 macerated concrete. Besides, this type of foundation also has a structure from broken brick concrete and cement mortar grade 50 or 100. The concrete lining part is responsible for cleaning and flattening the pit. It has the effect of preventing cement dehydration of the column. There is even a form-work for later pouring the concrete foundation.
  • The foundation, also known as the foundation plate: Usually has a rectangular, beveled bottom. The part has a moderate slope, less than 60 degrees. It is calculated to give the appropriate size for each type of construction.
  • The foundation neck is about 25mm larger than the foundation column in each direction. Its effect is to transmit forces and loads from the column to the bottom of the foundation.
  • The foundation brace is the part that supports the upper partition wall. At the same time, it also has the effect of reducing the differential settlement between the foundations. The foundation brace combined with the foundation beam can reduce the eccentricity of the foundation. It should be calculated as a beam in the bearing frame structure at that time.


When learning about single or cup nails, people need to keep a few things in mind:

  • The depth of foundation buried above the natural ground must be more than 1m.
  • In case of weak ground, do not use a single foundation structure. If you still want to use a single foundation, you must carefully calculate the layout. The base needs to be reinforced with bamboo poles.
  1. Single nail classification:

Nowadays, there are many different types of single nails. Each type of nail will have its criteria for classification. Specifically:

Types of single nails

Load characteristics:

If based on load characteristics, a single foundation has the following types:

  • The footing is centered correctly.
  • Eccentric load-bearing foundation. This type is usually located on the edge of the land.
  • Foundations for tall buildings. For example, water towers, tanks, chimneys, etc.
  • The foundation is subjected to large horizontal loads. This type of foundation is often used for retaining walls and dams.
  • Foundation can bear a vertical load, a small moment.


The following criterion for classifying a single foundation is hardness. Hard nails are nails with excellent hardness. It is considered equal to infinity. This type of foundation has low deformation. The deformation is considered close to zero. Currently, complex foundations include brick, stone, and concrete foundations. Specifically:

  • Weak foundation This foundation has the same deformability level as the subsoil. With excellent deformation properties much-bending resistance. In which, reinforced concrete foundation with long/short side ratio > 8 belongs to soft foundation.
  • A finite solid foundation is reinforced concrete with a long side/short side ratio ≤ 8.

If based on manufacturing factors, now there are the all-around foundation and assembled foundation. In particular, the block foundation is a type of foundation made of many different materials. It can be crafted at the construction site. It is also known as a poured-in-place foundation. Next is the mounting foundation. This type of foundation will be made of many prefabricated blocks put together when constructing the foundation.

There are different types of single nails.


Material is also used to go differentiated. Accordingly, there will be hard nails and soft nails. In there:

  • A rigid foundation is a foundation created with only compressive materials. With conventional foundation type, the height/width ratio of the foundation block is > 1/3. After being transmitted through the foundation, the load from above is redistributed on the ground. This type of foundation is applied where there is deep groundwater.
  • A soft foundation is created with materials subjected to tension, compression, and bending. The nail has a deforming characteristic similar to that of the base. It does not distribute pressure. This nail has any shape. Features are saving materials and fast construction time.
  1. Note when designing a single foundation:

Some necessary notes during the construction of a single foundation you need to grasp, namely:

  • In pouring concrete, make sure the pit is not flooded. Because if there is standing water, it will significantly affect the quality of concrete and the durability of the foundation when used.
  • When removing the formwork successfully, it is advisable to monitor and keep the excellent quality of the foundation to perform the next stage without interrupting the construction.
  • People often construct eccentric foundations with townhouses or not-so-beautiful foundations.
  • When constructing a single foundation, you need to pay attention to calculating the foundation tonnage, including indexes such as tonnage associated with the foundation bridge the width of the bottom surface. What is the standard strength of the ground,  what is the lateral load of a single foundation … and many more parameters.
  • Single footing steel shall be machined and of the best quality and dimensions. Make sure the drawing size is correct. The distortion, flattening, or deformation does not exceed the allowable level of 2%; stainless.

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