Masonry work is the process of building structures by laying individual units, such as bricks, concrete blocks, or natural stone, and binding them together with mortar. It’s one of the oldest and most durable construction methods, used for everything from residential walls and fireplaces to commercial buildings, walkways, patios, and retaining walls. Masonry can serve as the structural backbone of a building or as a decorative exterior layer, depending on how it’s designed.
Core Materials in Masonry
Three primary materials make up the vast majority of masonry construction: brick, concrete block, and natural stone. Each has distinct properties that make it better suited for certain applications.
Brick is formed from clay that’s shaped and fired in a kiln. It’s the material most people picture when they think of masonry. Bricks are remarkably strong in compression, typically handling 8,000 to 15,000 psi, and come in varieties for facing walls, paving, flooring, and even chemical-resistant industrial settings. They expand slightly over time, so masons build expansion joints into brick walls to prevent cracking.
Concrete masonry units (CMUs), commonly called cinder blocks or concrete blocks, are made from a stiff mix of portland cement and lightweight aggregate. They’re less expensive than brick, faster to lay because of their larger size, and typically have a compressive strength of 1,500 to 3,000 psi. CMUs come in solid and hollow forms, with the hollow cores often filled with grout and reinforcing steel for added strength. Unlike brick, concrete blocks shrink as they dry, so masons use control joints to manage where cracks appear.
Natural stone includes marble, granite, limestone, and fieldstone. Stone masonry can use precisely cut pieces for floors and wall cladding, or rough, naturally shaped rock for rustic walls and landscaping features. Stone is generally the most expensive masonry material but offers unmatched character and longevity.
The Role of Mortar
Mortar is the paste that bonds masonry units together. It’s a mix of cement, lime, sand, and water, and it does more than just glue bricks in place. Mortar compensates for slight size variations between units, seals joints against water, and distributes loads across the wall.
There are four standard mortar types, each rated by compressive strength and suited to different jobs:
- Type M (2,500 psi): the strongest option, used for below-grade work like foundations and retaining walls where soil pressure is a factor.
- Type S (1,800 psi): high strength with good bonding, common in exterior walls and areas exposed to lateral forces like wind.
- Type N (750 psi): the standard choice for most above-grade work, including brick veneer on homes and general-purpose walls.
- Type O (350 psi): a softer mortar used for interior, non-load-bearing walls and for repointing historic buildings where the original brick is soft.
Choosing the wrong mortar type causes real problems. Using a hard, high-strength mortar on soft historic brick, for example, leads to the brick itself cracking and spalling during freeze-thaw cycles because the mortar won’t flex. The mortar should always be softer than the masonry units it joins.
Solid Masonry vs. Brick Veneer
There are two fundamentally different ways masonry gets used in a building’s walls, and understanding the distinction matters if you’re buying a home, planning a renovation, or evaluating a structure.
Solid masonry walls are structural. The brick or stone itself carries the weight of the building. These walls are typically 8 inches thick or more, built with multiple layers (called wythes) of masonry. Buildings constructed before 1900 sometimes have solid masonry walls over 20 inches thick. Solid masonry relies on its sheer mass to absorb moisture that penetrates from the exterior. It’s incredibly strong and long-lasting, but it’s a poor insulator because brick doesn’t resist heat transfer well.
Brick veneer is the more common approach in modern construction. Here, the building’s structural support comes from a frame of wood, steel, or concrete behind the wall. The brick is a single layer applied to the exterior for appearance and weather protection, not for holding up the building. Between the veneer and the structural wall, there’s an open cavity that serves two purposes: it creates space for insulation (making veneer walls significantly more energy efficient than solid masonry), and it provides a drainage plane for any water that gets past the brick. Weep holes and flashing at the base of the wall allow trapped water to drain back outside.
Why Masonry Performs Well
Masonry’s reputation in construction comes down to a few key performance traits that other building systems struggle to match simultaneously.
Fire resistance is one of the biggest. Brick, block, and stone are non-combustible. A standard concrete block wall can achieve fire ratings of two to four hours depending on thickness, meaning it maintains its structural integrity for that long during a fire. This makes masonry a preferred material for fire walls, stairwell enclosures, and building separations.
Thermal mass is another advantage. Dense materials like brick and concrete absorb heat slowly, store it, and release it slowly. In climates where temperatures swing 10°C (18°F) or more between day and night, high-mass construction keeps indoor temperatures more stable by absorbing daytime heat and releasing it after dark. This effect is strongest when the mass is on the interior side of insulation. In traditional brick veneer, where the brick sits outside the insulation, it contributes little to thermal storage because it’s cut off from the indoor environment.
Durability is perhaps masonry’s defining trait. Properly built masonry walls can last centuries. The mortar joints are the component that eventually needs attention, but even they can last 50 to 100 years before requiring repair, depending on climate and exposure.
Tools and Techniques
Masonry is a hands-on trade. The core toolkit includes a brick trowel for spreading mortar beds, applying mortar to the ends of bricks, and trimming away excess material as each course is laid. Pointing tools, also called jointers, compress and shape the mortar joints after the mortar begins to set, creating smooth, weather-tight seams that protect the wall from moisture. Most masons carry a narrow jointer, a wide jointer, and a convex striker to handle different joint profiles.
Precision matters enormously. Spirit levels check that each course is plumb (vertically straight) and level (horizontally flat). String lines stretched between corners keep long runs of brick aligned. Squares verify that corners meet at true 90-degree angles. A wall that drifts even slightly out of plumb will compound the error with every course, so masons check constantly as they build.
Brick hammers and chisels cut units to size, though modern jobsites increasingly use wet saws for cleaner, more precise cuts. For large commercial projects, mechanical lifts and scaffolding systems allow masons to work efficiently at height.
Maintenance and Repair
Masonry is low-maintenance compared to most building materials, but it isn’t zero-maintenance. The mortar joints are the weak point, and over decades they erode from rain, wind, and freeze-thaw cycles. The repair process is called repointing (sometimes called tuckpointing): the deteriorated mortar is carefully removed to a depth of about three-quarters of an inch and replaced with fresh mortar.
Signs that repointing is needed include mortar that’s visibly receding or crumbling, gaps between the mortar and the brick, and stair-step cracks that follow the mortar joints in a diagonal pattern. Stair-step cracking often signals foundation settlement or thermal stress, which may need investigation beyond simple joint repair. If you notice damp spots on interior walls, musty smells, or peeling plaster, water has likely been infiltrating through failed joints for months before symptoms appeared inside.
The brick or stone units themselves rarely need replacement unless damage has occurred from impact, structural movement, or the wrong mortar being used. Spalling, where the face of a brick flakes off in layers, is a common consequence of hard cement mortar being applied to soft, older brick. The rigid mortar traps moisture in the brick, and when that moisture freezes and expands, the brick face pops off rather than the mortar absorbing the stress.
Building Codes and Standards
Masonry construction in the United States is governed by TMS 402/602, published by The Masonry Society. TMS 402 covers design requirements, while TMS 602 sets minimum construction standards. The current edition, published in 2022, is referenced by the 2024 International Building Code and includes updated provisions for masonry veneer design, new guidelines for composite reinforcement, and refined requirements for compression-controlled sections. These codes ensure that masonry structures meet safety thresholds for load capacity, seismic resistance, and fire performance.
Environmental Considerations
Masonry’s environmental footprint is a mixed picture. The building sector accounts for roughly 30% to 40% of global energy consumption and about a third of all carbon dioxide emissions. Masonry materials contribute to that total primarily through their manufacturing stage: firing clay bricks in kilns and producing the cement used in concrete blocks are both energy-intensive processes. For brick production, kiln firing is the dominant source of carbon emissions. For concrete blocks, cement manufacturing is the largest contributor.
On the other hand, masonry’s extreme durability means structures last far longer than those built with lighter materials, reducing the frequency of rebuilding and the associated resource use. The thermal mass properties of masonry can also reduce the energy needed for heating and cooling over a building’s lifetime, partially offsetting the upfront carbon cost. Some manufacturers now use recycled aggregates in concrete blocks, and research into sun-dried and geopolymer alternatives shows significant potential for reducing embodied carbon, with sun-dried bricks eliminating the kiln-firing emissions entirely.