In many construction projects, particularly where wood or steel structural materials are going to be used on a concrete foundation, J bolts are used to connect the two. The shape of these bolts makes them ideal for this job, allowing the hook or the curved bottom of the “J” shape to anchor with the rebar or in the concrete while the shaft is threaded to allow for tightening the structural material.

For these types of construction projects, the size of the bolts is determined based on the specific building code for the area. This may be the IRC or the International Residential Code or a code specific to the construction location. Another common guideline in use is the Residential & Light Construction Standards. Knowing what code to use will be critical not only to be able to pass inspection but also for safety.

Diameter and Length

All codes will specify the diameter and length of J bolts required for the given use of the bolts. For the majority of construction types of applications, the minimum diameter is usually one half of an inch.

The length of the J bolt needs to take into consideration both the depth that the hook will be inserted into the concrete as well as the height above the surface to accommodate for the material to be attached to the slab. There will also need to be enough height for the shaft over the surface of the attached component to allow for the washer and nut to be secured.

In most applications for residential construction, the bolt should be embedded at least seven inches into the reinforced concrete floor.

Custom sizes and shapes of J bolts can be supplied by some manufacturers. These are often required for specialized types of projects and jobs where the standard sizes of bolts are simply not up to the demands of the job.