Concrete Anchor Selection Guide: Load Requirements, Installation, and Code Compliance

Choosing the right concrete anchor can make or break a job. Whether you're hanging heavy equipment, securing structural connections, or mounting fixtures, the anchor you choose has a direct impact on safety, load capacity, and long-term performance. The wrong anchor selection will lead to callbacks, safety issues, and potential liability problems that no contractor wants to deal with after a long day of work.

Concrete anchor types tend to vary and can include concrete screws, hammer-set anchors, lag shields, lead screw anchors, plastic wall plugs, anchor bolts, and more. Masonry and concrete anchor types, for example, are often categorized as light-duty, medium-duty, or heavy-duty, depending on the weight they're able to support.

The key factors affecting anchor performance include:

1. Concrete strength and age
2. Load requirements (tension vs. shear)
3. Environmental conditions (moisture, temperature, chemicals)
4. Installation quality and hole preparation
5. Seismic and vibration considerations

Understanding these variables helps professionals on jobsites choose the right anchor system for each concrete application or project, while making sure that they’re staying code-compliant.

The most popular type of mechanical fasteners are called controlled expansion anchors, which have an advantage over chemical anchors as these anchors work by expanding against the concrete hole walls to create a mechanical interlock.

Wedge anchors consist of a threaded rod with an expansion sleeve and a wedge mechanism at the embedded end. When the nut is tightened, the wedge is drawn into the sleeve, causing it to expand and grip the concrete hole walls.

Installation Process:

1. Drill a hole to the specified diameter and depth
2. Clean the hole thoroughly with a wire brush and a blow-out bulb (this is an important step!) or make sure that it's deep enough to accommodate embedment depth
3. Insert the anchor through the fixture and into the hole
4. Tighten the nut to the specified torque

Best Applications:

1. Structural steel connections
2. Horizontal, vertical, and overhead installations
3. Cracked and uncracked applications
4. Heavy machinery mounting
5. Seismic and static load capabilities
6. High-load applications requiring permanent installation

Load capacities: Wedge anchors typically offer the highest load capacities among mechanical anchors, with larger diameters capable of handling thousands of pounds in both tension and shear when properly installed in high-quality concrete.

Lastly, Drop-in anchors create flush-mounted threaded connections in concrete when used. They're installed by dropping the anchor into a drilled hole and expanding it with a setting tool (Both of which are needed to use these anchors).

Installation Requirements:

1. Drill a hole using the specified diameter carbide drill bit according to instructions and regulations.
2. Insert the Drop-in anchor into the hole and tap until flush.
3. Use the designated setting tool on site to drive the expander plug.
4. Ensure proper setting with visible indentations.
5. Insert bolt or threaded rod, ensuring minimum thread engagement.

Limitations:

1. Cannot be removed once installed
2. Require separate machine screws or bolts
3. Not suitable for overhead applications without additional safety measures

Applications:

1. Mechanical installations requiring secure anchoring
2. Electrical setups needing reliable base material connections
3. Plumbing systems that require durable anchor points
4. Concrete Anchoring

There are several types of chemical anchors available, including epoxy, polyester, and acrylic, that are offered by Simpson Strong-Tie. Each adhesive anchoring type has its own unique properties, and they’re suitable for different applications.

Chemical or adhesive anchors create bonds through adhesive systems rather than mechanical expansion. Bonded (chemical) anchors are most resistant to very high loads, as they can carry up to 200 kg in hollow substrates, and 800 kg in solid substrates.

Epoxy anchors are known for their high strength and chemical resistance, making them ideal for heavy-loaded demanding anchoring applications.

Injection Systems:

1. Pre-mixed cartridges with mixing nozzles
2. Faster installation
3. More consistent mixing
4. Better for production work

Applications:

1. Structural connections in seismic zones

2. Doweling applications in new or existing concrete

3. Heavy-duty anchoring in commercial and industrial construction

4. Use in temperature extremes

5. Marine environments

Things to consider when installing adhesive anchors

According to  ACI 318 D.2.2 , adhesive anchors must be installed in concrete that has a minimum age of 21 days at the time of anchor installation. Temperature significantly affects cure time, with cold weather extending working time and cure periods.

Polyester chemical anchors are recognized for their rapid curing times and affordability, making them ideal for medium-load applications in various materials, including brick, concrete, and stone.

Advantages:

1. Faster cure times than epoxy (often 10-45 minutes)

2. More cost-effective for medium-duty applications

3. Good weather resistance

4. Suitable for both solid and hollow substrates

Typical Applications:

1. Rebar doweling

2. Utility attachments

3. Moderate structural connections

4. HVAC equipment mounting

Acrylic systems offer the fastest setting times among adhesive anchors, often allowing load application within minutes of installation.

Characteristics of Acrylic Adhesive Anchors:

1. Rapid cure (5-15 minutes typical)

2. Good for non-structural applications

3. Temperature sensitive

4. Lower ultimate strength than epoxy

Best Uses:

• Non-structural attachments
• Anchoring threaded rod and rebar into cracked and uncracked concrete
• Cold weather and wet concrete installations
• Grout-filled CMU construction
• Temporary applications
• Structural anchoring in compliance with IBC and IRC
• Quick turnaround projects

Self-tapping concrete screws have become increasingly popular in construction for light to medium-duty projects because they’re easy to install and remove when needed.

Installation Requirements:

1. Pilot hole slightly smaller than the screw diameter

2. Carbide-tipped masonry bit

3. Proper embedment depth

4. Torque control to prevent overtightening

Applications:

1. Fastening wall-to-wall

2. Beam and splitting reinforcement

3. Electrical boxes and conduit installation

4. Switch boxes and light fixtures mounting

5. Window and threshold anchoring

These anchors offer the fastest installation for medium and heavy-duty fastening applications into concrete and grout-filled block, making it so users only need a hammer for setting.

Advantages:

1. No special tools required

2. Very fast installation

3. Low cost

4. Good for repetitive applications

Limitations:

• Limited load capacity
• Not suitable for overhead applications
• Difficult to remove
• Performance varies with concrete hardness

Applications:

1. Concrete Block: Fast installation for electrical boxes, conduit straps, and light-duty structural connections in hollow CMU walls
2. Grout-Filled Block: Reliable anchoring for equipment brackets, pipe hangers, and medium-load attachments where the grouted core provides solid backing
3. Heavy-Duty Applications: Quick setting for structural connections, seismic retrofits, and high-load mounting points requiring immediate holding power
   

Choosing the right anchor starts with understanding the forces your installation will have throughout its lifetime of use. Every anchor point on the jobsite experiences different combinations of tension (pull-out), shear (sideways), and combined loading conditions that directly impact which fastener will perform reliably.

The concrete strength, hole preparation quality, and environmental factors like temperature swings and corrosive conditions all work together to determine your anchor's actual holding capacity. Getting the load analysis right from the start prevents callbacks, ensures code compliance, and keeps your installations safe, regardless of whether you’re planning to mount a simple electrical box or anchor critical structural connections on beams.

Understanding load types is key to proper anchor selection:

Tension Loads:

Tension loads differ when it comes to anchors because they represent the pull-out forces acting away from the concrete surface in critical overhead applications on the jobsite. These tension loads are known to be affected by concrete strength and anchor embedment.

1. Pull-out forces acting away from the concrete surface
2. Critical for overhead applications
3. Affected by concrete strength and anchor embedment
   
   

Shear Loads:

Shear loads, for example, are different from tension loads because the forces act parallel to the concrete surface. It’s common in structural connections and may require special considerations for edge distances.

1. Forces acting parallel to the concrete surface

2. Common in structural connections

3. May require special consideration for edge distances

Combined Loads:

1. Most real-world applications involve both tension and shear

2. Requires interaction calculations per ACI 318

3. May govern anchor selection in many cases

Minimum Concrete Strength: Most anchors require a minimum concrete compressive strength of 2,500 psi, although higher strengths may be necessary for maximum load capacity.

Cracked vs. Uncracked Concrete:

1. Cracked concrete significantly reduces anchor capacity
2. Special anchor designs are available for cracked concrete
3. Seismic applications typically assume cracked concrete conditions

Hole Preparation: Clean holes ensures a secure bond, boosting load capacity. Proper hole preparation includes:

1. Correct diameter and depth

2. Clean, dry holes free of debris

3. Proper bit selection for concrete type

4. Adequate hole cleaning procedures

Corrosion Resistance: These include carbon steel, 304 stainless steel, and 316 stainless steel. 304 stainless steel is suitable for areas with moisture and water present, but 316 stainless steel can withstand chemicals and water submersion.

Temperature Effects:

The temperature is important when deciding on the type of anchor to utilize in a project because the expansion and contraction cycles will affect the performance. It’s something that you must take into consideration, especially with chemical anchors, because they are particularly sensitive to temperature during installation. In places that experience high temperatures like Las Vegas, Nevada, or Phoneix, Arizona, the working time may be significantly reduced due to safety reasons.

Temperature

1. Expansion and contraction cycles affect anchor performance

2. Chemical anchors are particularly sensitive to temperature during installation

3. High temperatures may reduce working time significantly

Seismic Considerations: ACI 318-11 and ACI 318-14 seismic anchor calculations do not have to be performed if the earthquake component of the factored load acting on the anchorage is less than or equal to twenty percent of the total factored load acting on the anchorage.

Hole Drilling:

1. Use sharp, appropriately sized carbide bits
2. Maintain a consistent drilling speed
3. Avoid overheating the bit
4. Ensure hole depth meets specifications

Cleaning Procedures:

1. Remove all drilling debris

2. Use wire brushes and blow-out bulbs

3. Verify hole cleanliness before anchor insertion

4. Follow the manufacturer's specific cleaning requirements

Torque Specifications:

1. Use calibrated torque wrenches
2. Follow the manufacturer's torque values
3. Account for lubrication effects
4. Verify proper installation with proof testing when required

ACI 318 Requirements: For the first time, ACI 318–11 includes a design provision for adhesive anchors in concrete. Previously, adhesive anchors were designed according to provisions found in both the ICC Evaluation Service (ICC-ES) AC308 and ACI 318–08.

ICC-ES Evaluation Reports:

• Required for most structural applications
• Provide verified load capacities
• Include installation requirements
• Specify quality control procedures

Testing Requirements: Twice the maximum allowable tension load or one and a quarter (11/4) times the maximum design strength of anchors as provided in an approved test report using criteria adopted in this code or determined in accordance with Chapter 17 of ACI 318.

The right anchor selection means understanding the demands of each jobsite. Mechanical anchors provide a reliable and immediate loading capacity with straightforward installation procedures. Chemical anchors offer a better performance in more challenging or unique conditions, but they require more careful attention to installation procedures and environmental hazards.

For structural applications, always verify that your chosen anchor system has appropriate ICC-ES evaluation reports and meets ACI 318 requirements. When in doubt, consult with the anchor manufacturer's technical support team or a qualified structural engineer for guidance.

Investing in proper anchor selection and installation pays in terms of reduced callbacks, improved safety for you, the crew, and the structure, and your professional reputation. Stay current with code changes and manufacturer updates to ensure installations meet the latest standards and best practices.

Key Takeaways:

1. Match the anchor type to load requirements and environmental conditions

2. Follow the manufacturer's installation procedures exactly

3. Verify code compliance through ICC-ES reports

4. Clean hole preparation is critical for all anchor types

5. Consider the total installed cost, not just the material cost

6. When in doubt, consult technical resources

Additional Resources:

1. ACI 318 Building Code Requirements for Structural Concrete

2. ICC-ES Evaluation Service reports

3. Manufacturer technical data sheets

4. Local building code requirements

Some additional resources to keep in mind include, but are not limited to, ACI 318 Building Code Requirements for Structural Concrete, ICC-ES Evaluation Service reports, manufacturer's technical data sheet, and local building code requirements.