In large commercial masonry projects, even the strongest walls face internal stress due to temperature changes, moisture, and settlement. Over time, these forces can lead to cracking — unless properly managed. That’s where masonry control joints come into play.
So, what is a control joint in masonry? How does it work in commercial buildings? And why is it so crucial for long-term durability?
Let’s break it down simply and thoroughly.
What Is a Masonry Control Joint?
A masonry control joint is a deliberate, planned separation between sections of a masonry wall designed to manage cracking caused by shrinkage, thermal expansion, or movement. These joints allow the wall to flex slightly and absorb stress without visible cracking.
It’s easy to confuse control joints with expansion joints, but the difference is key:
- Control joints manage shrinkage and minor thermal changes in materials like concrete block (CMU).
- Expansion joints accommodate larger-scale movement between different building components or materials.
In commercial settings with large, continuous walls, control joints are vital to maintaining clean, crack-free surfaces and structural performance.
Why Control Joints Are Essential in Commercial Masonry
In commercial masonry construction — think shopping centers, schools, factories, hospitals — walls can span hundreds of feet. Without proper control joints, those expansive walls would be at high risk of unsightly cracks or even structural compromise.
Here’s why control joints matter in commercial masonry:
- Prevents Cracking: Masonry naturally expands and contracts. Control joints absorb movement and stop stress from turning into visible cracks.
- Supports Long-Term Durability: Control joints preserve the structural integrity of masonry walls over decades.
- Improves Appearance: Cracks in building façades look unprofessional. Control joints help keep walls smooth and clean.
- Ensures Code Compliance: Most building codes and specifications (such as from the NCMA or ASTM) require joints in specific intervals to reduce risk.
In short, control joints protect both the appearance and the performance of commercial masonry walls.
Types of Masonry Control Joints Used in Commercial Buildings
There are a few main types of control joints used in commercial masonry projects:
Vertical Control Joints
These are the most common, typically running from the top to the bottom of the wall. They’re especially useful in long, uninterrupted stretches.
Horizontal Control Joints
Less frequent, but used in walls with stacked CMU or multi-story construction to handle vertical shrinkage.
Preformed Control Joints
These come with compressible inserts and are installed during wall construction — ensuring uniform width and flexibility.
Field-Formed Joints
Formed using bond breakers or other temporary materials that are removed later and filled with sealant.
Regardless of type, the goal is the same: allow the wall to move safely without cracking.
Placement of Masonry Control Joints in Commercial Structures
Proper placement of control joints is essential. Here’s how experts decide where to place them in commercial buildings:
- Every 20 to 30 feet in straight walls (standard industry guidance)
- At wall openings: doors, windows, or loading docks
- Where walls change direction or height
- At structural supports or changes in the foundation level
- At wall intersections, especially where different materials meet
For example, in a commercial warehouse or large retail plaza, you might see joints:
- On every long CMU wall section
- Beside each entry door
- Above and below the large window installations
The objective is to break the wall into flexible panels that can shift slightly without causing cracks.
Design Considerations and Best Practices
Installing control joints isn’t just about cutting a line in the wall — it’s a precise process. Consider the following:
- Coordinate Early: Control joints should be included in the architectural and structural drawings from the start.
- Reinforcement Breaks: Horizontal joint reinforcement (like ladder wire) must be interrupted at control joints to allow movement.
- Use the Right Materials: Backer rods and high-quality sealants allow for flexibility and long-term durability.
- Maintain Consistency: Joints should continue through multiple wythes of masonry — interior and exterior — for continuity.
From both a functional and aesthetic point of view, joints should be placed symmetrically and in alignment with the building’s design intent.
Common Mistakes to Avoid in Masonry Control Joint Installation
Even experienced teams can run into issues when control joints are improperly planned. Here are some common mistakes to avoid:
- Incorrect Spacing: Ignoring recommended spacing (e.g., exceeding 30 ft) often leads to cracking.
- Poor Joint Sealing: Using low-quality or improperly installed sealants can lead to leaks and joint failure.
- Skipping Joints at Openings: Wall openings are weak points — failing to place joints near them is a major oversight.
- Failure to Coordinate with Reinforcement: Reinforcement running through the joint negates its purpose.
Avoiding these errors is key to a high-performance commercial wall system.
Frequently Asked Questions (FAQs)
What is the standard spacing for masonry control joints in commercial buildings?
Typically, every 20 to 30 feet for CMU walls, depending on wall height, exposure, and structural design. More aggressive spacing may be needed in seismic zones or high-moisture areas.
Can you add control joints to an existing masonry wall?
Yes, though it’s more complex. Retrofit control joints involve cutting through the wall and carefully sealing the new joint to prevent water intrusion.
Are control joints required by building codes?
Yes, many commercial building codes and masonry standards (like NCMA TEK notes and ACI) recommend or require control joints to manage movement and prevent damage.
How do control joints affect the structural integrity of CMU walls?
Properly placed control joints enhance structural integrity by reducing the chance of stress-related cracking. They work in conjunction with reinforcement and grout to allow flexibility without failure.
Conclusion: Why Masonry Control Joints Matter in Every Commercial Project
At Leidal and Hart, we’ve seen firsthand how proper masonry control joints make or break the long-term success of a commercial build. From industrial plants to multi-story offices and healthcare centers, every project benefits from thoughtful joint design.
We don’t just lay bricks — we build resilient, code-compliant, and aesthetically aligned masonry systems that stand the test of time. Whether you’re starting a new project or retrofitting an existing one, our team has the experience, insight, and craftsmanship to do it right the first time.
Need expert help with commercial masonry design or control joint installation?
Let’s talk. At Leidal and Hart, we’re committed to delivering excellence, joint by joint, wall by wall.
