Concrete Anchors vs Screws: Which is the Real Workhorse for Your Project?

Installing anything on concrete inevitably requires choosing the right fastener. The two main options are concrete anchors and concrete screws. But when should you use each type?

When to Choose Concrete Anchors

Concrete anchors are fasteners that are secured into pre-drilled holes in concrete. They work by either expanding outward through pressure or wedging against the hole for a tight, permanent hold.

Some of the most common types of concrete anchors include:

• Sleeve anchors - use a metal sleeve that expands outward to grip the concrete
• Wedge anchors - wedge-shaped ends expand when the bolt is tightened
• Drop-in anchors - set into place with a hammer then expanded with a bolt
• Screw anchors - a screw inserted into a plastic shell fixed in the concrete

Compared to concrete screws, anchors can support much higher load capacities. Their large size and expansive installation method allows them to distribute weight more evenly. Anchors are a popular choice for heavy-duty tasks like:

• Mounting large equipment or machinery to walls and floors
• Structural supports in commercial buildings
• Securing heavy beams, columns, and bracing
• Permanent signage or artwork installations

For heavyweight loads or applications that require exceptional strength, anchors are typically the best option. Their holding power and shear strength excel in industrial settings.

Anchors are also ideal for permanent installations. Once fully expanded and set, anchors are extremely secure. Removing or relocating them takes extra work.

Overall, concrete anchors are the go-to fastener when sheer strength and holding power is paramount.

When Concrete Screws Are the Better Option

In contrast to anchors, concrete screws are designed to be directly driven into concrete without any pre-drilling. The screws cut into the concrete as they are inserted using specialty threads and tips.

Some key benefits of concrete screws include:

• Faster installation since no pre-drilling is required
• Easily removable and reusable
• Lower cost than most anchors
• Less likely to crack weak or fragile concrete

While screws have a lower load capacity than many anchors, they can still securely hold light to medium loads. They are a convenient option for tasks like:

• Hanging pictures, shelves, or light cabinets to walls
• Mounting TVs, cameras, or other electronics
• Securing fixtures, rails, or tracks
• Assembling prefab furniture anchored to the floor

Concrete screws also excel when you need a removable or temporary fastener. Since screws can be unscrewed without damaging the concrete, they allow furniture, equipment, and other items to be relocated. Permanent anchors would damage the concrete trying to remove them.

Finally, concrete screws are often the best choice when working with weaker concrete, such as aerated autoclaved concrete used in prefab construction. The porous material can crack easily with inserts like anchors. Concrete screws are designed to bore into the concrete without cracking it.

Key Differences Between Anchors and Screws

Installation Method

The primary difference between anchors and screws is the installation method.

Anchors require pre-drilling a hole into the concrete that is the same diameter as the anchor. After cleaning the hole of debris, the anchor is inserted and then expanded or wedged into place with tools.

Concrete screws simply get screwed in using a drill much like a wood screw. No pre-drilling or setting is needed. Just drive in the screw to the proper depth.

Load Capacity

When it comes to load capacity, concrete anchors are the clear winner. Popular anchors can hold over 1,000 lbs per fastener. Screws max out around 500 lbs.

Here are some typical load capacities:

• 3/8" sleeve anchor - 1,000 lbs
• 1/2" wedge anchor - 2,100 lbs
• 3/16" screw anchor - 180 lbs
• 1/4" tapcon screw - 265 lbs

For heavy equipment, structural supports, or commercial applications, anchors provide the ultimate holding strength.

Cost Comparison

Concrete anchors are sold as a system involving the anchor bolt, expansion mechanism, and tools for installation. This makes them more expensive per unit than concrete screws.

For example, a 3/8" x 3" sleeve anchor may cost $2-3 each. Comparable sized tapcon screws can cost under $1 per screw.

For large projects demanding hundreds of fasteners, screw's cost savings add up quickly. Anchors become pricey at scale.

Permanence and Removability

When installed correctly, concrete anchors form an extremely permanent hold. Their wedging or expansion inside the concrete makes anchor removal very difficult. Screws, on the other hand, can be unscrewed and reused easily.

If you ever need to access whatever you've secured to the concrete, screws make maintenance and adjustments much simpler. Anchors are for one-time permanent mounting.

Material Compatibility

Concrete screws are made specifically to work with different types of concrete:

• Standard concrete screws - Normal concrete
• Aerated concrete screws - Weak, porous concrete
• Masonry screws - Concrete block (CMU)

Anchors are more universal but can crack weak concrete when pre-drilling. Always check screw specs for recommended concrete types.

Choosing the Right Concrete Fastener

With all of their differences, how do you know whether concrete anchors or screws are best for your particular project?

Here are some key factors to consider:

Load Capacity Needs

Determine how much weight the fasteners need to support. For heavy loads exceeding 500 lbs per anchor point, traditional anchors are the better choice.

For lighter duties like hanging decorations or securing table legs, concrete screws have plenty of strength.

Permanence of the Application

Think about whether you'll need to access whatever is being mounted regularly. Concrete screws allow easy removal. Anchors become permanent attachments.

Type of Concrete Used

Know your specific concrete type and strength. Regular concrete anchors work fine in most concrete. For weaker or more porous mixes, specialized screws are safer.

If Pre-Drilling is Feasible

Anchors require pre-drilling holes. For thin concrete or locations hard to access with a drill, screws are easier to install.

Time Constraints

Since anchors need drilling and setting, screws are much faster for time-sensitive projects. Dozens can be installed in the time it takes to set a few anchors.

When feasible, consulting an experienced engineer is wise for choosing appropriate fasteners for large commercial and structural projects.

Concrete Screw and Anchor Varieties

While this comparison focuses on basic concrete anchors and screws, many specialty varieties exist for specific needs:

Specialty Anchors

• Epoxy anchors - bonded with epoxy instead of friction
• Seismic anchors - meet earthquake safety codes
• Undercut anchors - for anchoring close to edges
• Screw anchors - a hybrid screw and anchor

Concrete Screw Types

• Hex washer head - provides a washer and hex drive
• Flat head - countersunk screw profile
• Philips flat head - flat head with Philips drive
• Tamper-resistant - avoid unwanted removal

Many other variations exist for specific needs. Always consult manufacturers to find the optimal fastener.

Proper Installation Techniques

To get the full strength and effectiveness from concrete anchors and screws, proper installation is critical.

Drilling Guidelines for Anchors

• Use a hammer drill and carbide bit for drilling holes
• Drill holes slightly deeper than the anchor embedment depth
• Clean holes thoroughly with a wire brush or compressed air
• Ensure anchors sit completely flush in the hole when set

Correct Concrete Screw Installation

• Use an impact driver on a low setting to avoid stripping the head
• Drill holes if needed for edge or spacing requirements
• Drive screws to the recommended depth; not too shallow or deep
• Ensure screws are straight and flush without cracking concrete

Always follow the particular anchor or screw manufacturer's instructions for best results.

Frequently Asked Questions

Can concrete anchors and screws be used in cinder blocks?

No, concrete block, also called CMU (concrete masonry unit), requires specialized masonry anchors and tapcon masonry screws. Do not substitute standard concrete fasteners in block.

How do I determine the right size anchor or screw for my load?

Consult manufacturer load tables to find options rated for at least 125% of the expected load for safety. An engineer can also calculate exact requirements.

Can I reuse a concrete screw that has been driven in previously?

No, concrete screws should only be driven once. The threads get damaged during initial insertion and won't grab as tightly if reused. Old holes can be redrilled for new screws.

What causes concrete screws to break?

The main reasons for screw breakage are overtorquing, bad drill technique, or improper concrete. Use an impact driver on the right setting for the screws and particular concrete material.

Do anchors and screws cause cracks in concrete?

Improperly installed anchors can crack concrete by exerting too much pressure. Concrete screws crack fragile concrete if the wrong screw type is used. Always use the properly rated fastener for the concrete.

Now that you know the differences between concrete anchors and screws, you can confidently choose the best option for your next project.

For heavy loads and sheer strength, traditional anchors are the gold standard. When easy installation and removability matter, screws are ideal.

Consider the expected load capacity, permanence needs, concrete type, and your installation constraints. With the right selection criteria, picking anchors versus screws becomes straightforward.

While advanced fasteners exist for special applications, these two core options cover most basic concrete mounting needs. Know when to use anchors versus screws, and you can tackle any concrete project with confidence.