When your support system needs to connect directly to a concrete ceiling, wall, or floor, you need a fastening method built for the job. That’s where concrete inserts come in. Designed to be embedded in concrete before it cures — or installed into existing concrete — these specialized hardware components create permanent, load-rated attachment points for strut channel, pipes, conduit, and other structural components.

In this guide, we’ll cover everything you need to know about concrete inserts for strut channel systems: how they work, the types available, and how to choose the right insert for your application.

What Is a Concrete Insert?

A concrete insert (also called a cast-in-place insert or concrete anchor) is a metal fitting that is embedded in a concrete slab or structure to provide a threaded or slotted connection point for hanging or supporting loads. Unlike post-installed anchors that require drilling into cured concrete, cast-in-place inserts are installed before the concrete is poured, resulting in a stronger, flush connection.

For strut channel systems, concrete inserts allow you to attach channel nuts and fittings directly to a concrete ceiling or wall — no drilling, no anchor bolts, and no hole in the finished surface.

What Are the Different Types of Concrete Inserts?

Slotted (Linear) Concrete Inserts

These are the most common type for strut channel systems. A slotted insert is embedded face-down in a concrete slab and creates a continuous slot — identical to the slot in standard strut channel — along the underside of the slab. Channel nuts can then be inserted and slid to any position along the slot, providing the same infinite adjustability you get with surface-mounted channel.

Steinco carries Unistrut slotted concrete inserts in both standard duty and heavy duty configurations, as well as Flex-Strut concrete inserts.

Spot (Point) Concrete Inserts

Spot inserts provide a single, fixed attachment point rather than a continuous slot. They are typically used when load points are pre-determined and the flexibility of a slotted insert isn’t required. Steinco carries Unistrut spot inserts including the P3245 and related components in our strut accessories catalog.

Seismic Concrete Inserts

For installations in seismic zones, specially rated concrete inserts provide the additional pull-out and shear strength required by ASCE 7 and IBC seismic provisions. Steinco carries seismic concrete inserts as part of our complete seismic support system offering.

Prestressed Concrete Inserts

Standard inserts are not suitable for use in prestressed or post-tensioned concrete slabs. Specialized prestressed concrete inserts (such as the Unistrut P3165 series) are engineered to avoid cutting or damaging the prestressing tendons during installation.

How Are Concrete Inserts Installed?

Cast-in-Place Installation

Cast-in-place inserts are installed in the concrete formwork before the pour:

  • Position the insert face-down on the form, with the slot or connection point oriented toward the finished face of the slab
  • Secure the insert to the form using the hold-down clips or tie wires provided
  • Pour the concrete and allow it to cure
  • Strip the form — the insert face is now flush with the slab underside, ready for channel nut installation

Working with Existing Concrete

If inserts weren’t installed before the pour, your options include post-installed mechanical anchors, epoxy anchors, or screw anchors. These are different products from cast-in-place inserts but serve a similar function in retrofit situations. Contact our team for guidance on the best anchor system for your specific concrete substrate.

What Load Ratings Do Concrete Inserts Have?

Load ratings for concrete inserts depend on the insert type, the concrete compressive strength (f’c), embedment depth, and spacing from edges and other inserts. Unistrut provides detailed load tables in their engineering documentation, and projects in seismic zones will require additional review per IBC/ASCE 7 requirements.

As a general guideline, standard Unistrut P3253 slotted inserts in 3,000 psi concrete are rated for approximately 2,000–3,000 lbs allowable load per insert, depending on direction and spacing. Always verify with the manufacturer’s current engineering data for your specific conditions.

Concrete Inserts vs. Post-Installed Anchors: Which Should You Use?

If you have the opportunity to install inserts before the pour, cast-in-place inserts are almost always the better choice:

  • Stronger: Cast-in-place inserts typically achieve higher load ratings than post-installed anchors in the same concrete
  • No drilling: Eliminates the risk of cutting reinforcing steel or damaging the slab structure
  • Flush surface: The finished slab face is unbroken — important in food processing, pharmaceutical, and clean room facilities
  • Cost-effective: Insert hardware is inexpensive; the savings in later drilling and anchor installation often more than offset the upfront cost

Frequently Asked Questions About Concrete Inserts

Can concrete inserts be used in walls as well as ceilings?

Yes. Slotted inserts are commonly cast into precast concrete wall panels to support pipe runs, conduit, and equipment in commercial and industrial facilities. The installation process is the same as for slab inserts.

Are Unistrut concrete inserts compatible with Flex-Strut channel nuts?

For the 1-5/8″ series, Unistrut inserts and Flex-Strut channel nuts are generally compatible because they share the same slot dimensions. However, always verify compatibility with the specific products you’re using before committing to a system.

Do I need a structural engineer to specify concrete inserts?

For simple, low-load applications, manufacturers publish load tables that allow qualified contractors to select appropriate inserts without engineering review. For heavy loads, seismic applications, or installations in prestressed concrete, a licensed structural engineer should verify the insert selection and layout.

Source Concrete Inserts Through Steinco Industrial Solutions

Steinco carries the complete range of Unistrut and Flex-Strut concrete inserts for 1-5/8″ metal framing systems. Whether you need cast-in-place slotted inserts, spot inserts, or seismic-rated components, we can supply them with fast turnaround to your jobsite in Ohio and throughout the region.

Contact Steinco to request a quote or to discuss your specific application requirements. Our technical team has over 30 years of experience with strut framing systems and can help you select the right insert configuration for your project.