What is Anchor Bolt?

An anchor bolt is a type of fastener designed to connect a house wood component to a concrete surface. It means you will see it between the foundation wall (a concrete component of the house) and the Sill plate (a wood component of the house). It is obvious home builders use these fasteners to make sure these two components are connected in any circumstances. There are different kinds of anchor bolt in the market depends on its design and purpose of usage, an illustration of some is provided in pictures.

The Usage

This fastener protects houses from Tension Forces (Action of Pulling) and Shear Forces (Acting in the lateral direction on an object). Examples of these forces could be Wind and Earthquake. As a result, they are very important to be present and installed correctly. Any damaged or broken bolts and concrete around the bolt should be addressed and repaired by a Qualified Contractor or Structural Engineer.

These are not the only kind in the market so there is a chance you find another type, too. As Home Inspectors, during Crawl Space Inspection we try to locate them as much as they are visible to make sure they are:

  • Present
  • Not Broken or Damaged
  • Not exposed to Concrete Damages Surrounding Them


What the International Building Code (2018) says about Anchor Bolt Installation?

Bolts shall extend not less than 7 inches (178 mm) into concrete or grouted cells of concrete masonry units. The bolts shall be in the middle third of the width of the plate. A nut and washer shall be tightened on each anchor bolt.

There shall be not fewer than two bolts per plate section with one bolt located not more than 12 inches (305 mm) or less than seven bolt diameters from each end of the plate section.