Masonry, CMU, Mortar, Grout, and Brick Veneer Properties
Key Takeaways
- Masonry behavior comes from an assembly of units, mortar, grout, reinforcement, connections, and workmanship rather than from unit strength alone
- Mortar beds and bonds units, while grout fills designated spaces and develops reinforcement; concrete, mortar, and grout are not interchangeable names
- Use net or gross section properties exactly as required by the TMS 402/602-16 design method and the stated grouting pattern
- Reinforced masonry relies on compatible reinforcement and grouted cells for tensile force transfer, while unreinforced masonry has limited tensile resistance
- Anchored or adhered brick veneer carries its own loads and transfers out-of-plane actions to backing but is not automatically a structural bearing or shear wall
- Movement joints, flashing, drainage, ties, shelf support, corrosion protection, and differential movement are part of veneer performance
Masonry, CMU, Mortar, Grout, and Brick Veneer Properties
Use TMS 402/602-16 with its companion commentaries and IBC 2018 without supplements for a July 2026 exam question. Masonry is an assembly. A high-strength concrete masonry unit does not by itself establish wall strength, and a brick appearance does not establish a structural bearing wall.
Know each constituent's job
| Constituent | Structural or construction role | Common trap |
|---|---|---|
| Concrete masonry unit (CMU) | Provides face shells, webs, cells, compression area, and geometry | Treating nominal dimensions or gross area as solid concrete |
| Clay brick or structural unit | Provides unit strength, geometry, durability, and bond surface | Assuming every brick wythe is veneer or every brick veneer is bearing |
| Mortar | Beds units, accommodates dimensional variation, bonds joints, and transfers local stress | Selecting the strongest mortar without considering compatibility and specification |
| Grout | Fills designated cells or cavities and bonds reinforcement to masonry | Treating grout as mortar or assuming every cell is grouted |
| Reinforcement | Carries designed tension and contributes to shear or compression behavior | Counting a bar whose cell is ungrouted or improperly consolidated |
| Anchors and ties | Transfer out-of-plane veneer or wall forces and accommodate specified movement | Using them as gravity support without a designed load path |
CMU dimensions are often nominal; actual dimensions account for mortar joints. Hollow units concentrate material in face shells and webs. The design method may use net cross-sectional area, effective area, or transformed properties. Follow TMS notation and the stated grouting layout. A fully grouted wall and a partially grouted wall with the same nominal thickness do not have the same weight, stiffness, or effective section.
Mortar type is selected for the required masonry system, unit absorption, exposure, workability, and structural properties under TMS 402/602-16 and the project specification. More compressive strength is not automatically better bond, water resistance, or movement accommodation. Grout must flow into specified spaces, surround reinforcement, and be placed and consolidated under the construction requirements. Mortar protrusions or debris can block cells and compromise grout continuity.
Reinforced and unreinforced behavior
Masonry is strong in compression but comparatively weak and variable in tension. Unreinforced masonry therefore depends heavily on compression, geometry, axial load, and permitted tensile provisions. It should not be credited with reinforced behavior merely because metal accessories are nearby.
Reinforced masonry uses bars placed in grouted cells or bond beams so tensile forces can transfer through grout and bond into the units and mortar assembly. Bar location matters: moving a bar changes effective depth and moment strength. Lap lengths, cover, cell cleanliness, grout consolidation, and continuity at intersections affect whether the analytical load path exists. The specified masonry compressive strength f'm characterizes the masonry assemblage; it is not the individual CMU strength, mortar cube strength, or grout-cylinder strength.
For walls, distinguish in-plane shear and flexure from out-of-plane pressure response. Axial load can alter flexural behavior and slenderness effects. Openings interrupt wall piers and bond beams, requiring forces to flow through lintels, jamb reinforcement, collectors, and foundations. Material property selection is only the start of system design.
Brick veneer is a facing system
Anchored masonry veneer is attached to backing with anchors or ties and commonly has a cavity. The veneer carries its self-weight to a foundation ledge, shelf angle, or other designed support and transfers out-of-plane wind or seismic pressure through ties to the backing. Ties must have appropriate capacity, spacing, embedment, corrosion protection, and movement capability.
Adhered masonry veneer transfers its weight and out-of-plane forces by bond through the specified setting system to a suitable backing. Its substrate preparation, mortar layers, bond, water management, and installation limits follow IBC 2018 and TMS provisions. “Adhered” does not mean its gravity or environmental load disappears.
Neither type should automatically be counted as part of the structural backing's thickness, bearing capacity, or lateral-force-resisting system. The backing wall or frame remains responsible for assigned building loads unless the structural design explicitly qualifies another role. Conversely, calling veneer nonstructural does not make it harmless: its weight, anchors, eccentricity, support, and falling hazard are structural demands.
Exterior veneer must also accommodate different thermal and moisture movement between brick, CMU, concrete, steel, or wood backing. Shelf angles, soft joints, expansion joints, flashing, weeps, drainage cavities, and water-resistive layers have distinct functions. A rigid tie or blocked cavity can turn normal movement or water into cracking and corrosion.
Worked load-path example
A 12-ft-high structural CMU wall is idealized for preliminary dead load as 8 in (0.667 ft) thick with an equivalent assembly unit weight of 90 pcf. Per foot of wall length,
wCMU = 90(0.667)(12) = 720 lb/ft = 0.72 klf.
A brick veneer weighs 40 psf of wall surface, so its line weight is
wveneer = 40(12) = 480 lb/ft = 0.48 klf.
If both are supported by the same foundation ledge, the preliminary vertical reaction is 0.72 + 0.48 = 1.20 klf, before other loads and factors. If the veneer instead bears on a shelf angle at an elevated floor, its 0.48-klf weight follows the shelf angle and frame load path; it should not be added blindly to the CMU footing line.
For a separate tie illustration, suppose nominal out-of-plane pressure is 30 psf and one tie receives 2.0 ft² of tributary veneer. Its nominal force is 30(2.0) = 60 lb. Final design still uses the prescribed load combinations, tie capacities, spacing limits, embedment, backing connection, and any flexible-anchor provisions. Tributary force alone does not approve a tie layout.
Exam workflow
Identify whether the element is structural masonry, backing, anchored veneer, or adhered veneer. Trace gravity and out-of-plane forces separately. Then select the assembly property, grouting pattern, reinforcement, effective section, and movement details from the exact TMS 402/602-16 and IBC 2018 provisions. This prevents a material label from replacing the actual wall system.
Which statement correctly distinguishes mortar from grout in a reinforced CMU wall?
How should anchored brick veneer normally be represented in the building load path?
A 12-ft-high veneer weighs 40 psf of wall area. What vertical line load does it create at its gravity support?