Anchor Bolts – Specification and Types

Anchor bolts are a type of fastener used to attach parts (e.g., equipment’s, structure, tanks, or any other material) to concrete foundations.

One side of the anchor bolt is inserted into the concrete foundation before the concrete cures and hardens, allowing for a secure hold once the material is set.

The other side of the anchor bolt (threaded side) is used to bolt the part on the concrete foundation.

Anchor bolt application for Foundation

Anchor bolts are commonly used in construction projects such as buildings, towers, bridges and other structures. They can also be found in varied applications from ceiling fans to wall mountings.

Types of Anchor Bolts

Anchor bolts are an essential part of many construction projects. They are used to secure items such as wooden beams, steel columns, and other structures to concrete foundations.

There are several types of anchor bolts available for different applications as:

  1. Straight Anchor Bolt,
  2. Welded Nut Anchor Bolts,
  3. Nut & Plate welded anchor bolts,
  4. J-Type Anchor bolt (Bent-bar Anchor Bolts),
  5. L-Type Anchor Bolt (Bent-bar Anchor Bolts),
  6. Square and round U Bend Anchor Bolts,
  7. Wedge concrete anchor bolts,
  8. Stud concrete anchor bolts,
  9. Strike anchor bolts,
  10. Self-Drilling Concrete Anchor bolts,
  11. Pigtail anchor bolts.

Straight Anchor Bolt

A straight anchor bolt is a type of anchor bolt with a straight threaded end and a hexagonal head. These bolts are used to secure items such as structural supports and building frames to concrete foundations or other materials.

Straight anchor bolts are available with welded nut, welded plate and without.

Image credit- Mafco
Image: Campbell

J-Type Anchor bolt

J-Type Anchor bolts have become a popular and reliable choice for fastening applications. Used in both light and heavy duty projects.

They are made of steel and provide superior holding power to secure fixtures in concrete or masonry.

These anchor bolts have a J-shaped configuration that is embedded into the concrete or masonry material.

L-Type Anchor bolt (Bent-bar Anchor Bolts)

The L-Type Anchor Bolt, also referred to as the bent-bar anchor bolt, is a heavy-duty fastening device used for anchoring structural applications.

The anchor bolt is made from high strength steel and has a L shape with 90-degree, 120 degree or 135-degree angles on each end.

This allows the anchor bolt to be embedded into concrete or masonry structures where it provides maximum holding power and stability.

Bent-bar Anchor Bolts

Square and round U Bend Anchor Bolts

Square and round U bend anchor bolts are a simple yet effective way to secure objects in place.

These anchor bolts feature a unique design that allows them to be easily installed in any material, from wood to concrete or other materials.

Image: Portland

Square and round U Bend Anchor Bolts are commonly used for securing heavy machinery and equipment in place, as well as for hanging signs or banners.

They can also be used for supporting the structural integrity of walls or creating secure foundations when installing foundation anchors.

Wedge concrete anchor bolts

A wedge concrete anchor bolt is a type of mechanical fastening system used to secure objects into masonry walls or in concrete.

The wedge concrete anchor bolt is most often made from high-grade steel for maximum corrosion resistance and strength.


The shape of the wedge creates a strong hold that grips into masonry materials as it expands outward when tightened. This ensures that the object being secured remains firmly anchored even under extreme tension or pressure.

How is Anchor bolt fixed?

Anchor bolts are an essential part of any structural build, and it is important to understand how anchor bolt is fixed in order to ensure a secure and safe structure.

Anchor bolts are fixed during the civil concrete laying stage. Although anchor bolt can be fixed at later stage also. Usually for high loading conditions, anchor bolts are fixed during concrete pouring.

Anchor bolts are typically embedded into concrete foundations during the pour, with the total process taking only a matter of minutes.

Drilling can also be used to fix anchor bolt. To begin, a hole must be drilled into the foundation for the anchor bolt to fit.

Once this has been done, epoxy or grout can be used to fix the anchor bolt in place.

The hole should be wide enough so that there is at least one inch clearance between the outside of the anchor bolt and concrete walls.

Afterward, an expansion shield can be added around the base of each bolt to increase resistance against pull-out force when tension is applied on them.

This will help keep your structure securely anchored even if environmental conditions cause movement or settlement in its foundation.

Selecting the Right Anchor Bolt

Anchor bolts are essential for a range of applications, from securing heavy machinery to holding down roofing materials.

Selecting the right anchor bolt is an important task that should not be taken lightly. An anchor bolts shall have the designed service life, corrosion resistance, and strength to withstands the load without failure & deformation.

There are several factors to consider when choosing the anchor bolts as listed below:

  • Anchor bolt material.
  • Anchor bolt length and diameter,
  • Type of application (for wall or civil foundation),
  • Corrosion resistance,
  • Strength of the anchor bolt,
  • heat treatment condition for the anchor bolt,

Length of the Fastener or Anchor Bolts

According to the NCMA, the length of an anchor bolt embedded in concrete shall be 4d or 2-inches (whichever is higher), where d is the nominal diameter of the anchor bolt.

Although always follow the designer’s recommendation for engineered foundations. The above value is a thumb rule only.

The minimum length requirement of an anchor embedded in concrete is determined by calculating the distance from the concrete top to inside.

This ensures that sufficient anchorage capacity can be maintained in order for safe and secure performance.

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