The inspector's role in masonry construction oversight, the regulatory framework, and what the special inspector must understand before any masonry work begins.
The Masonry Special Inspector's Role
Masonry construction involves a layered sequence of materials - units, mortar, grout, and reinforcement - each placed by hand in conditions that change by the hour. Unlike a factory process, masonry construction cannot be evaluated after the fact with any reliability. Once grout has hardened and units are in place, most of the critical inspection points are buried and inaccessible. This is why special inspection of masonry is continuous or near-continuous for reinforced masonry - because the inspection opportunity exists only once, while the work is being placed.
IBC Chapter 17 and the TMS 402/602 masonry code both establish inspection requirements for structural masonry. The quality assurance level required - Level A, B, or C - determines the extent and frequency of inspection activities. Level C requires the most comprehensive oversight, including continuous inspection during grout placement and unit laying for critical elements. The statement of special inspections identifies which QA level applies to the project, and the inspector must understand what that designation requires before arriving on site.
IBC Section 1705.4 – Special inspection of masonry; TMS 402 Section 1.6 – Quality assurance; TMS 602 Article 1.6 – Quality assurance inspection requirements; IBC Table 1705.4 – Required special inspection of masonry.
Masonry inspection requires close coordination with the masonry contractor's foreman. Understanding the daily work plan - which walls will be laid, when grout pours are scheduled, where mortar will be batched - allows the inspector to be in the right place at the right time. Inspectors who wait for the contractor to call them are always reacting rather than planning, and on fast-moving projects, critical inspection points can be missed entirely.
Pre-construction masonry inspection checklist: (1) Review structural drawings and identify all masonry elements requiring special inspection. (2) Confirm which QA level applies and what inspection frequency is required. (3) Review masonry specifications for approved unit types, mortar types, and grout mix designs. (4) Request and review masonry material submittals - unit certifications, mortar materials, grout mix design. (5) Confirm approved mix designs and proportions are on file. (6) Identify all locations requiring grout sampling and prism testing. (7) Establish schedule for inspection with the masonry contractor.
Quality Assurance Levels and Inspection Frequency
TMS 402 establishes three quality assurance levels that govern the extent of inspection required. The level assigned to a masonry element depends on its structural importance, whether it is a special inspection element under IBC, and the design method used. Higher QA levels require more frequent verification of materials, proportions, and placement conditions. For the inspector, the QA level is the lens through which every inspection decision is made - it determines whether presence during a grout pour is mandatory or periodic.
Certain activities within masonry construction are mandatory hold points regardless of QA level - events that must be inspected before the work proceeds or is covered. Grout placement is the most critical. Once grout is placed and the cells are filled, the reinforcement position, the grout consistency, and the consolidation method cannot be verified without destructive investigation. The inspector must be present for grout pours and must observe the full operation from mixing through consolidation.
TMS 402 Table 1.6.1 – Minimum quality assurance requirements by QA level; TMS 602 Article 1.6 – Inspector duties for each QA level; IBC Table 1705.4 – Masonry special inspection requirements.
A common mistake is treating periodic inspection as optional oversight. When a QA level calls for periodic inspection, the inspector must still appear regularly enough to verify that the work in progress conforms to the documents. Showing up once a week on a fast-moving masonry project is insufficient. Periodic means at intervals adequate to verify conformance - which requires judgment about the pace of work and the complexity of the details.
Concrete masonry units, brick, and other masonry materials - specifications, properties, and what the inspector verifies.
Concrete Masonry Units and Clay Brick
Concrete masonry units - commonly called CMU or concrete block - are the most prevalent masonry unit in structural applications. They come in a range of sizes, configurations, and strengths. Standard block is 8 inches nominal in height and depth; width varies based on wall thickness. Structural masonry uses units conforming to ASTM C90, which establishes minimum net area compressive strength, absorption limits, and dimensional tolerances. The inspector must verify that delivered units match the specification and that defective units are not incorporated into the work.
Clay brick for structural applications must meet ASTM C62 or C216, depending on the application and grade required. Grade SW brick is for severe weathering exposures; Grade MW is for moderate weathering. The compressive strength, absorption, and saturation coefficient of clay brick vary by grade and affect both the masonry's structural performance and its durability. In exterior structural masonry, the grade selection must match the exposure category identified on the drawings.
ASTM C90 – Standard specification for loadbearing concrete masonry units; ASTM C62 – Standard specification for building brick; ASTM C216 – Standard specification for facing brick; TMS 602 Article 2.3 – Masonry unit requirements.
When material is delivered to the site, the inspector should verify that the units are accompanied by the required certifications and that the delivered product matches what was approved in the submittal. Pay attention to the strength designation - a Type N block might be delivered in error when Type S was required. Inspect units for excessive cracking, spalling, or dimensional defects before they are incorporated into the work. Damaged units that find their way into the wall create weak points that are impossible to identify after the fact.
The specified compressive strength of masonry (f'm) used in design is based on the unit strength and mortar type per TMS 402 or on prism test results. The designer's assumed f'm must match the actual materials delivered. If units of lower strength are substituted without engineering review, the actual masonry strength may be insufficient for the design loads.
Concrete Masonry Unit Classification, Grades, and Inspection at Delivery
ASTM C90 governs loadbearing concrete masonry units (CMU). Units are produced in Grade N (suitable for exterior use and below-grade construction) and Grade S (limited to above-grade exterior walls protected by weather-resistant finish or interior use). Face shell thickness, web thickness, and compressive strength requirements differ by unit weight classification: Normal Weight (NW), Medium Weight (MW), and Light Weight (LW). The inspector must verify at delivery that units are labeled with the manufacturer, ASTM designation, grade, and nominal dimensions. Units with chips, cracks through webs, or face shell thickness below minimum must be rejected.
ASTM C90 minimum requirements for 8-inch CMU: Minimum face shell thickness: 1.25 in. (NW/MW) or 1.0 in. (LW). Minimum web thickness: 1.0 in. Minimum net area compressive strength: 1,900 psi for single units; 1,350 psi net area for composite. Net area calculation: (gross cross-section minus void area) used for compressive strength verification. Grade N vs Grade S distinction: Grade N approved for any exposure; Grade S for interior and protected exterior only per ASTM C90 Section 5.
ASTM C90 (loadbearing CMU); ASTM C129 (non-loadbearing CMU); IBC Section 2103.1; ACI 530.1 Section 2.3 (material requirements).
Accepting Grade S CMU for an exterior application without verifying that the design specifies a weather-resistant coating or cladding to qualify the reduced exposure condition. Grade S units without protection in a direct weather exposure condition are a code violation.
Clay Brick Grades, Types, and Efflorescence Inspection
Clay brick is covered by ASTM C216 (facing brick) and ASTM C62 (building brick). ASTM C216 establishes Grade SW (severe weathering, freeze-thaw exposure) and Grade MW (moderate weathering) based on durability under weathering. Facing brick is further classified Type FBS (standard tolerances), Type FBX (extra precision), and Type FBA (architectural, allows non-uniform appearance). The inspector must verify that the brick grade and type match the project specification and check delivery lots for efflorescence, spalling, cracking, or dimensional non-conformance by sampling per ASTM C67 before accepting the material.
Efflorescence visible on new brick at delivery indicates soluble salts in the clay body or manufacturing batch. While some efflorescence disappears after installation and weathering, pre-existing efflorescence at delivery is a flag that the material may have been inadequately fired or stored in wet conditions. Photograph affected units and document the lot number. The structural engineer and architect should review before the lot is accepted or rejected.
ASTM C216 (facing brick); ASTM C62 (building brick); ASTM C67 (sampling and testing brick); IBC Section 2103.2; ACI 530.1 Section 2.3.2.
Accepting Grade MW brick for an exposed exterior application in a freeze-thaw climate. Grade MW brick does not have the tested durability for severe weathering conditions. In climates with more than 15 freeze-thaw cycles per year, Grade SW brick is required for exposed exterior faces. Substituting MW for SW without design modification is a code violation.
Mortar types, proportioning requirements, mixing procedures, and field inspection of mortar quality.
Mortar Types and Proportioning
Masonry mortar serves multiple functions: it bonds units together, distributes loads across the bed joint, accommodates slight dimensional variations in units, and provides the substrate for reinforcement bar positioning. TMS 602 recognizes four structural mortar types - M, S, N, and O - distinguished primarily by their compressive strength and cement-to-lime ratios. Type S mortar is the most commonly specified for structural masonry because it provides good compressive strength combined with adequate flexibility.
Mortar may be proportioned by the proportion method or the property method. The proportion method specifies the volume ratios of portland cement, masonry cement, lime, and sand without testing. The property method requires that the mixed mortar meet minimum strength and flow requirements by laboratory testing. Most specifications for structural masonry use the proportion method for simplicity, but the inspector must verify that the specified proportions are actually being batched in the field - and this requires watching the batching process, not just inspecting the finished joint.
TMS 602 Article 2.1 – Mortar materials; TMS 602 Table 2.1 – Mortar proportions by volume; ASTM C270 – Standard specification for mortar for unit masonry; ASTM C780 – Standard test method for preconstruction and construction evaluation of mortars.
A major practical challenge with mortar inspection is that the mason's judgment about mortar consistency often overrides the mix design. Masons routinely add water to mortar that has stiffened from evaporation - a practice known as retempering - which is acceptable only within the initial working life of the mix. Mortar that is retempered beyond its working time produces weaker, less durable joints. The inspector must understand the working life limits of the mortar type specified and watch for signs that old mortar is being reworked beyond those limits.
Using masonry cement in mortar without verifying its compatibility with the specification is a common field error. Some specifications restrict or prohibit masonry cement in structural applications because its ingredients and production vary between manufacturers. If the specification requires portland cement and lime, the inspector must confirm that masonry cement is not being substituted without engineering approval.
Mortar Joint Inspection and Joint Types
The bed joint is the horizontal mortar joint; the head joint is the vertical joint between units in the same course. TMS 602 specifies that bed joints should be 3/8 inch thick for most applications, with tolerances of plus or minus 1/8 inch. Consistent joint thickness affects both the coursing of the wall and the uniform distribution of load. Thick, irregular joints can concentrate stress at points of reduced contact area between unit and mortar.
The joint tooling profile affects both appearance and weather resistance. Concave-tooled joints are the most durable for exterior exposures because the tooling compresses the mortar surface and forces it against the unit faces. Flush joints and raked joints leave mortar less compressed and more vulnerable to water infiltration. The specification should identify the required tooling profile; the inspector verifies it is being applied consistently.
Head joints must be filled solidly in structural masonry. Unfilled or partially filled head joints reduce the structural integrity of the masonry panel and can create paths for water infiltration in exterior walls. Inspectors sometimes find that head joints are only filled at the face of the wall while the interior of the joint is left void - a practice that produces walls that look acceptable on the surface but are structurally compromised. Checking the interior of head joints before the next course is laid catches this problem before it is concealed.
Mortar joint inspection procedure: (1) Measure bed joint thickness at multiple locations using a tape measure and verify tolerance per TMS 602. (2) Visually inspect head joint filling before each course is covered by the next - look for voids by checking the interior of the joint. (3) Verify joint tooling profile matches specification after initial set. (4) Check mortar coverage on the unit face - mortar should extend to both face shells. (5) Document any consistently deficient areas with location references.
Grout mix requirements, placement procedures, consolidation methods, and the inspector's critical role during grout pours.
Grout Mix Design and Properties
Masonry grout is not the same as concrete - it is a flowable cementitious mixture specifically designed to fill the cells of masonry construction. Grout comes in two types: fine grout and coarse grout. Fine grout uses fine aggregate only and is used in cells or cavities too small for coarse aggregate. Coarse grout includes aggregate up to 3/8 inch and is used in larger cells. The minimum cell dimension required for each grout type is specified in TMS 602 and must be verified against the actual masonry unit dimensions.
Masonry grout must be fluid enough to fill all voids in the cell without segregation or bridging. TMS 602 requires a grout slump of 8 to 11 inches - much wetter than structural concrete - to ensure complete flow around reinforcing bars and into all corners of the cell. Inspectors must verify slump at the point of placement, not at the mixer. Grout that arrives at the pump or bucket in compliance may stiffen significantly during transport on a hot day.
TMS 602 Article 2.2 – Grout materials; TMS 602 Table 2.2 – Grout proportions by volume; ASTM C476 – Standard specification for grout for masonry; ASTM C1019 – Standard test method for sampling and testing masonry grout.
Grout samples for strength testing must be taken at the point of placement, not at the mixer or the truck. ASTM C1019 describes the grout prism fabrication procedure using masonry unit sections as molds. The prisms are fabricated in the field during the pour and cured under the same conditions as the masonry. The inspector is responsible for taking the samples, properly labeling them, and ensuring they are transported to the laboratory without damage. Grout strength results directly verify the design assumed f'm for grouted masonry.
Grout Placement and Consolidation Inspection
Grout placement in masonry must be performed in lifts not exceeding the height limits specified in TMS 602. The lift height depends on the grout slump and whether mechanical consolidation will be used. Low-lift grouting fills cells from the bottom up in stages aligned with masonry coursing; high-lift grouting places grout in taller lifts after the full wall panel height has been laid. Each method has specific requirements for consolidation and reconsolidation that the inspector must monitor.
Grout must be mechanically consolidated using vibration or rodding to eliminate voids and ensure that the grout fully surrounds all reinforcing bars and fills all cell corners. Vibration is the more reliable method for coarse grout in large cells. The vibrator must be inserted at regular intervals and withdrawn slowly to avoid creating channels or segregating the aggregate. Reconsolidation - a second vibration pass after the grout has settled slightly - is required by TMS 602 to eliminate settlement voids that form as the grout loses water to the surrounding masonry units.
Grout pour inspection sequence: (1) Prior to pour, verify all cells to be grouted are clean and free of mortar droppings, debris, or standing water. (2) Confirm reinforcement is in correct position before any grout is placed. (3) Verify grout slump at the point of placement - sample the first truck or batch. (4) Observe placement method and lift heights - confirm lifts do not exceed TMS 602 limits. (5) Observe vibration - note vibrator diameter, insertion interval, and duration. (6) Observe reconsolidation after initial settlement. (7) After pour, verify tops of grouted cells are struck off flush if required. (8) Document pour location, lift heights, slump measurements, and any deficiencies.
Inspectors sometimes allow grout to be placed without mechanical consolidation when the contractor claims the grout will self-consolidate due to its high slump. High slump alone does not guarantee complete fill - grout can bridge over mortar protrusions and leave voids, particularly around reinforcing bars. Unless a self-consolidating grout specifically qualified under ASTM C1017 and approved for the project is being used, mechanical consolidation is required.
Checking cell cleanliness before a grout pour is one of the most overlooked pre-pour inspection steps. Mortar droppings accumulate inside CMU cells during unit laying. These droppings, if not cleaned out, can block grout flow and create voids. Some specifications require cleanout openings at the base of walls for tall grout lifts specifically to allow debris removal and visual confirmation of cell conditions before grouting.
Reinforcement requirements for structural masonry - bar grades, placement tolerances, splices, cover, and inspection procedures.
Reinforcing Bar Placement and Tolerances
Reinforcing steel in masonry must be placed as shown on the structural drawings before cells are grouted. Unlike concrete construction, where a cage is assembled and the concrete is placed around it, masonry reinforcement is often placed incrementally as each course is laid. The inspector must verify bar size and position before grout is placed, because once grouted, the reinforcement is permanently concealed. This is the fundamental reason why inspection during placement - not after - is essential.
Minimum cover requirements for masonry reinforcement protect the bars from corrosion and ensure adequate bond between the grout and bar. TMS 402 specifies minimum cover requirements based on exposure conditions. Bars in exterior masonry exposed to weather require more cover than interior bars. The inspector must verify that bars are positioned to achieve the specified cover before grouting begins, because cover cannot be adjusted after the fact.
TMS 402 Section 6.1.6 – Reinforcing bar cover in masonry; TMS 602 Section 3.4 – Placement of reinforcement; ASTM A615 – Standard specification for deformed and plain steel bars for concrete reinforcement; ASTM A706 – Low-alloy steel deformed bars (for seismic applications).
Reinforcement inspection procedure: (1) Verify bar size and grade from the bar markings against the drawing schedule. (2) Check bar spacing against the structural drawings using a tape measure - spacing tolerances are typically plus or minus 1 inch. (3) Verify bar position within the cell - centered bars should be approximately centered; bars at specific cover distances should be checked with a gauge. (4) Confirm splice lengths where bars are lapped - measure and document. (5) Verify horizontal joint reinforcement (ladder or truss type) is installed at the courses specified. (6) Check that bars are continuous and not cut short. (7) Document locations, sizes, and spacings in the inspection log.
Masonry reinforcement is typically shown on a structural plan view with horizontal bars in plan and vertical bars indicated by spacing notation. Wall sections and detail sheets show bar sizes, spacing, cover requirements, and splice locations. The masonry schedule or notes block on the structural drawings often summarizes vertical bar spacing and horizontal reinforcement requirements by wall type designation. The inspector should prepare a summary of reinforcement requirements organized by wall location before going to the field.
Horizontal Joint Reinforcement and Ladder vs. Truss Wire Differences
Horizontal joint reinforcement (HJR) is embedded in the mortar bed joint to control shrinkage cracking, provide shear transfer, and satisfy MSJC/ACI 530 minimum prescriptive reinforcement requirements in some wall configurations. HJR is available in two main configurations: ladder type (parallel longitudinal wires connected by perpendicular cross wires) and truss type (longitudinal wires connected by diagonal cross wires). Truss type reduces the grout space in the cell below the joint and can interfere with vertical rebar placement. The project specification will identify which type is required. The inspector must verify the wire size, spacing, and lap length at joints match the specification.
ASTM A951 wire requirements for HJR: Minimum wire diameter: W1.7 (9 gauge) for joint reinforcement in non-structural walls; W2.1 (8 gauge) for joint reinforcement used as structural reinforcement. Spacing: typically 16 inches o.c. vertical for 8-inch CMU. Lap splices: minimum 6 inches at corners and intersections. Material: hot-dip galvanized ASTM A153 Class B for exterior or below-grade; mill galvanized Class B-1 for interior. Embedment: fully surrounded by mortar on all sides.
ASTM A951 (masonry joint reinforcement); TMS 402 Section 6.1 (horizontal reinforcement); ACI 530.1 Section 3.4A (installation requirements); IBC Section 2103.11.
Installing truss-type HJR in cells scheduled to receive vertical bar and grout. The diagonal wires of truss-type reinforcement can obstruct vertical bar placement and interfere with grout consolidation. Ladder-type reinforcement must be specified and used in grouted cell locations.
Vertical Rebar Installation - Cover, Tolerance, and Continuity Verification
Vertical reinforcing bars in grouted masonry must be positioned correctly before grout is placed, because repositioning after grout sets is impossible. ACI 530.1 Section 3.4 requires bars to be held in position during grouting using bar positioners, ties to HJR, or other approved means. The specified concrete cover - typically 1.5 inches to the face of grout for interior exposure - must be maintained. Continuity of vertical reinforcement at bond beams and floor connections must be verified: lap splice lengths are specified in TMS 402 and depend on bar size and development length.
Vertical rebar inspection sequence: Step 1 - Verify bar size and spacing match structural drawing callout in each cell. Step 2 - Check bar position within cell: bar must not be touching the cell face shell (min 1.5 in. clear cover to grout surface). Step 3 - Verify bar is supported to prevent displacement during grouting (bar positioner, tie wire, or HJR tie). Step 4 - For lap splices at story height: verify lap length per structural drawing and TMS 402 Table 6.1.8.12.4. Step 5 - Document any out-of-tolerance bars before grout pour.
TMS 402 Section 6.1.8 (development and splice requirements); ACI 530.1 Section 3.4B (bar placement tolerances); IBC Section 2104.1.
Verifying rebar size but not verifying bar is held in the correct cell. A rebar in the wrong cell (one bay off from the drawing) cannot be discovered after grout is placed. The inspector must cross-reference bar location to the structural drawing, not just verify presence and size.
How masonry is constructed - laying sequence, bonding patterns, construction tolerances, and what the inspector watches for during laying operations.
Laying Sequence, Bond Patterns, and Construction Tolerances
Masonry construction proceeds course by course, with each course of units placed on a freshly spread mortar bed and head joints filled as the units are laid. The structural stability of the wall during construction depends on the masonry gaining adequate early strength before subsequent courses impose significant load. This is particularly important in tall walls where construction loads from scaffolding, materials, and workers can stress partially cured masonry. The inspector should understand the construction sequence and flag situations where load is applied to green masonry prematurely.
TMS 602 specifies construction tolerances for masonry work that the inspector verifies using a level, plumb bob, and measuring tape. The wall must be plumb and level within specified limits. Individual courses must be level within tolerance. The wall face must not deviate from the design plane by more than the tolerance for bowing or misalignment. These tolerances exist because masonry out of plumb concentrates load eccentrically, reducing the effective capacity of the wall.
TMS 602 Article 3.2 – Construction tolerances for masonry; TMS 602 Article 3.3 – Laying masonry units; IBC Section 2103 – Masonry construction requirements.
Checking plumb and level is a continuous inspection activity during masonry work, not a one-time verification at the end. Correcting a wall that is out of plumb by two inches after ten courses have been laid is difficult and costly. Catching a developing lean after two or three courses allows the mason to correct it before it compounds. The inspector who walks the wall regularly during laying prevents the kinds of problems that trigger disputes at the end of a project.
A frequent field problem is laying units without adequate mortar coverage on the bed joint face shells. Hollow-core CMU walls are not solid - only the face shells are mortared, not the interior webs. If mortar is not placed on the full width of each face shell, the effective bearing area is reduced, lowering the wall's compressive capacity. The inspector should periodically lift a freshly laid unit to verify full mortar coverage on the bearing surfaces before the mortar sets.
Weather Conditions and Masonry Protection
Cold weather masonry construction requires active protection of fresh mortar and grout from freezing. Mortar or grout that freezes before achieving adequate strength will have permanently compromised bond and compressive capacity. TMS 602 defines specific temperature thresholds and required protective measures - including enclosures, heating equipment, and heated water and materials - that must be in place before masonry can be placed when air temperature falls below the specified limits.
Hot weather masonry presents the opposite challenge - mortar and grout lose workability and moisture too rapidly to the atmosphere, shortening the working life of the mix and reducing the time available for placing and adjusting units. TMS 602 requires protective measures in hot, dry, or windy conditions to slow moisture loss. The inspector should verify that materials are not excessively heated before use and that protective measures are implemented when ambient conditions require them.
TMS 602 Article 1.8.3 – Cold weather requirements; TMS 602 Article 1.8.4 – Hot weather requirements; IBC Section 2104.3 – Preparation of mortar under cold weather conditions.
Temperature requirements in the masonry code are based on ambient temperature - the temperature of the air where the work is being done, not just the outside weather station reading. A heated enclosure can maintain workable conditions during cold weather, but the inspector must verify that the actual temperature inside the enclosure meets the minimum requirements throughout the work area, including at the masonry surface and at the base of the wall where cold air can settle.
Verifying the specified compressive strength of masonry through prism testing and unit strength methods.
Masonry Prism Testing and Unit Strength Method
The specified compressive strength of masonry, f'm, is the design basis for the structural calculations. If the actual masonry does not achieve f'm, the structure may be under-strength for its design loads. TMS 402 provides two methods for verifying f'm: the unit strength method, which uses the unit compressive strength and mortar type per a table, and the prism test method, which requires constructing and compressing masonry prisms fabricated with the actual project materials.
The prism test method provides direct verification of the actual masonry strength. Prisms are typically two to five units tall, fabricated using the same units, mortar, and grout as the project, and cured in a manner that reflects project conditions. ASTM C1314 governs the fabrication, curing, and testing of masonry prisms. The inspector must be present during prism fabrication to verify that the prisms accurately represent the project materials and workmanship.
TMS 402 Section 1.3 – Specified compressive strength; TMS 602 Article 1.4 – Verification of f'm; ASTM C1314 – Standard test method for compressive strength of masonry prisms.
Prism fabrication must occur during actual masonry operations using the same materials, same mortar mix, and the same mason performing the work. Prisms fabricated in a separate area under ideal conditions using freshly opened materials will over-represent the strength of the actual masonry. The inspector must document the batch numbers and material sources used in the prisms to confirm they match the production materials.
When prism test results come back below the specified f'm, the inspector's role is to document the results and notify the engineer of record immediately. The engineer must evaluate whether the deficiency is significant given the actual loads on that portion of the structure, and determine what corrective action - if any - is required. Do not delay notification waiting to see if later tests recover - low early results may indicate a systemic problem with the materials or workmanship.
Masonry Prism Testing - Procedure, Curing, and Result Interpretation
Masonry prisms for the prism test method (ASTM C1314) are constructed by the mason using the project materials and mortar, then cured and tested in compression. Prisms must be constructed with the same units, mortar type, and bedding configuration as the project masonry. For single-wythe CMU walls, a prism is typically 3 courses high with a height-to-thickness ratio of 2.0 to 5.0 after capping. Curing: 28-day moist cure at 75 +/- 15 degrees F. The test value f'm is the average of 3 prisms, and the individual results must not deviate by more than 15% from the average - if they do, the set is invalid and 3 additional prisms must be tested.
ASTM C1314 prism testing requirements: Minimum prisms per test: 3. Curing: 28 days at 75 degF, 90-100% RH or sealed. Geometry: height-to-thickness ratio between 2.0 and 5.0. Capping: sulfur compound or gypsum cap applied per ASTM C1552 within 24 hours of test. Test result: net area compressive strength per ASTM C1314 Table 1 correction factors applied for h/t ratio. Acceptance: set average must meet or exceed specified f'm; individual prism not more than 15% below average.
ASTM C1314 (prism testing); ASTM C1552 (capping); TMS 402 Section 1.3 (masonry specified compressive strength); ACI 530.1 Section 1.4.
Constructing prisms with mortar prepped for spread-ability (too wet) rather than at the job-site mortar consistency. Prisms must represent the actual mortar being used, including water content. Wetter mortar produces lower strength prisms and does not represent the project masonry. The inspector should witness prism construction during a typical working condition, not at a special demo mortar mix.
Unit Strength Method - When It Applies and What to Verify
The unit strength method allows f'm to be established from the certified compressive strength of the masonry units combined with the mortar type designation, per TMS 402 Table 1.4-2, without constructing and testing prisms. This method is only valid when the CMU or brick units have certified strengths meeting the minimum values in the table, the mortar is Type S or M mixed to the ASTM C270 proportion specification, and the grout (if used) meets the minimum strength per TMS 402 Table 1.4-4. The inspector must obtain and retain the manufacturer's certificate for the units and verify the mortar type designation in the project specification before using the unit strength method.
The unit strength method provides less quality control assurance than the prism test method because it relies on manufacturer certifications rather than tested samples from the actual project materials. On projects where strength is near the minimum required or where the masonry is critical to the lateral force-resisting system, the EOR may specify prism testing even when the unit strength method would be permitted. Always follow the EOR's direction over the minimum code permission.
TMS 402 Table 1.4-2 (unit strength method for CMU); TMS 402 Table 1.4-4 (grout strength requirements); ASTM C270 Table 2 (proportion specification for mortar); ACI 530.1 Section 1.4B.
Applying unit strength tables to masonry units without obtaining the manufacturer's certified compressive strength. The unit strength method is valid only when the unit strength is certified in writing by the manufacturer. A nominal strength designation on the delivery ticket is not a certification of compliance with ASTM C90 minimum strengths.
Inspecting anchor bolts, embedded plates, and connection hardware in masonry construction.
Anchor Bolt Inspection and Embedded Hardware
Anchor bolts and embedded hardware in masonry connect the structural system - transferring loads between the masonry wall and other structural elements such as roof diaphragms, ledger beams, and shear transfer hardware. These elements must be in the correct position, at the correct elevation, and properly embedded in grout to develop the strength assumed in the design. Once the masonry is laid and grouted around them, their position and embedment are fixed permanently.
Anchor bolt inspection procedure: (1) Verify bolt size, grade, and configuration match the structural drawings and bolt schedule. (2) Check horizontal position - measure from established reference points. (3) Verify bolt projection above masonry matches the dimension required for the connection hardware. (4) Confirm embedment depth - measure before grouting if possible. (5) Verify anchor bolts are properly supported and braced to prevent displacement during grout placement. (6) Observe grout consolidation around anchor bolt locations - these areas require careful vibration to ensure complete fill. (7) Document positions, sizes, and embedment depths.
Anchor bolts frequently get displaced during grout placement if they are not adequately secured before the pour. A template or fixture that holds all bolts in a group in their correct relative positions is essential for bolt groups that will receive structural hardware. Verify that any templates are still in position just before the pour begins and that bolts have not shifted during masonry laying operations in the area.
Anchor bolts placed at the wrong elevation are a frequent problem, particularly when the structure has sloped or variable-height bearing conditions. Bolts set too low may not engage the connection hardware properly; bolts set too high may not have adequate embedment. Verify embedment depth from the finished masonry surface elevation using the grout pour elevation as the reference, not the unfinished wall height.
Anchor Bolt Inspection Before and After Grouting
Anchor bolts set in masonry grout must be positioned and held in place before grout is placed, because correction after grout sets is extremely difficult. The inspector must verify bolt size, thread length above the masonry surface, projection height, and position relative to the center of the grout cell. TMS 402 requires minimum edge distance (1.5 bolt diameters to cell face), minimum embedment depth (per TMS 402 Table 9-A), and that the bolt is located in a fully grouted cell. Bolts in partially grouted cells are non-compliant.
TMS 402 anchor bolt requirements: Minimum bolt diameter: as specified on drawings. Minimum embedment depth: 4 bolt diameters or 2 inches, whichever is greater. Minimum edge distance: 1.5 bolt diameters or 2 inches from edge of grout space. Bolt must be in a fully grouted cell. Tolerance: bolt position +/- 1/4 inch from drawing location. Nut and washer: installed at project completion per structural drawing callout.
TMS 402 Section 9.1 (anchor bolts); ACI 530.1 Section 3.4C (installation); IBC Section 2104.1; ASTM F1554 (anchor bolt material specification).
Allowing workers to use bent rebar as anchor bolts when specified anchor bolts are unavailable. ASTM F1554 anchor bolts have specific mechanical and chemical properties that rebar does not match, particularly thread form and yield strength. Using rebar as an anchor bolt without EOR-approved substitution is a structural non-conformance.
Embedded Hardware, Lintels, and Pre-Installed Items
Beyond anchor bolts, masonry assemblies often include embedded steel plates, weld-on connectors, wire ties to adjacent frames, and lintel support angles. All embedded items must be verified against the structural drawings before they are covered by masonry courses. Lintels over openings are critical: the bearing length at each end must meet the minimum specified (typically 8 inches for most loads), and the lintel type (precast concrete, CMU bond beam, or steel angle) must match the design. A lintel with insufficient bearing can fail at a fraction of the design load.
Embedded plate installations are often performed by the structural steel erector before the mason arrives. When the plates were installed by a different trade, verify their location and orientation against the masonry drawing before the masonry encloses them. Out-of-position plates that are discovered after enclosure require costly core drilling and grout injection repair. Catch them during the rough frame walk-through.
TMS 402 Section 5.2 (lintels); ACI 530.1 Section 3.3B (embedded items); IBC Section 2103.11 (wall ties and connectors); IBC Section 2109.3 (lintel requirements).
Verifying lintel bearing length only on one side because the other side is against a concrete column. Both ends of the lintel require the minimum specified bearing length on a masonry or concrete surface, not just the free end. The lintel bearing at the column may require a pocket cast into the concrete, which must be verified separately.
Reading structural drawings for masonry - wall schedules, reinforcement layouts, connection details, and construction notes.
Masonry Wall Schedules and Structural Details
Structural drawings for masonry buildings typically include plan views at each floor level showing wall locations and references to wall type schedules or detail numbers. The wall schedule summarizes the reinforcement requirements for each wall designation - vertical bar size and spacing, horizontal reinforcement type and spacing, grouting requirements, and the specified masonry strength. Rather than reading every detail on every plan sheet, the inspector who understands the wall schedule can quickly identify what is required at any location on the project.
Connection details show how masonry walls attach to foundations, floors, and roofs. Foundation details show anchor bolt patterns, base course conditions, and the transition between the foundation and the wall. Floor-to-wall connection details show how diaphragm loads are transferred into the masonry - typically through ledger angles, bond beams, or embedded hardware. Roof anchorage details are particularly important in areas of high wind or seismic demand. The inspector should review all connection details before the work in that area begins.
Masonry drawings frequently have coordination issues between the architectural and structural sets, particularly at window and door openings where lintels, jamb reinforcement, and flashing details overlap between disciplines. When an architectural detail and a structural detail appear to conflict, do not guess which one governs - request a formal clarification from the engineer of record before the work proceeds. Field modifications made without engineering review can create unanticipated structural deficiencies.
The inspector's role is not to design the masonry but to verify that what is being built matches the approved drawings. When the mason foreman says a detail is impractical as drawn, that may be true - but the correct response is to request a revised detail from the engineer, not to improvise a field modification. Constructability issues should be raised before the work begins, at the pre-construction meeting, so that coordination problems can be resolved without schedule impact.
Reading Masonry Wall Schedules and Section Details
Masonry wall schedules are tables or keynotes on the structural drawings that cross-reference a wall type designation (e.g., W-2) to a specific cell configuration, reinforcing, grouting pattern, and mortar type. The schedule is the primary reference for determining whether a wall is partially grouted, fully grouted, or unreinforced. Section details show the vertical cross-section of the wall with bar sizes, vertical spacing, horizontal joint reinforcement spacing, and lintel conditions at openings. The inspector must read the wall schedule and corresponding section detail together, not either one in isolation.
Example masonry wall designation: W-3 (from schedule): 8-inch CMU, Type S mortar, vertical #5 bars at 48 in. o.c. in grouted cells, horizontal joint reinforcement at 16 in. o.c., partial grout (only cells with vertical bars grouted). Interpretation: Only cells containing #5 bars receive grout. Cells between vertical bars are ungrouted (hollow). The inspector verifies grout placement only in designated cells and rejects grout placed in non-designated cells.
IBC Section 2104.5 (inspection of masonry); ACI 530.1 Section 1.5 (submittal requirements); TMS 402 Section 6.1 (reinforcement requirements).
Using an elevation drawing to determine grouting requirements instead of the wall schedule. Elevation drawings show the visible face of the wall, not the interior cell configuration. A smooth face elevation drawing gives no indication of which cells are grouted. Always use the wall schedule and section detail for grout placement requirements.
Interpreting Structural Masonry Details at Beam and Column Connections
Where masonry walls connect to reinforced concrete or structural steel frames, the detail at the interface is critical for both lateral load transfer and differential movement accommodation. Common connection details include: wall ties to steel columns using dovetail slots, expansion anchors at concrete columns with soft joint filler, and bond beams at floor levels to transfer diaphragm shear into the masonry. The inspector must verify that the expansion joint width and filler material at column-to-wall interfaces match the architectural detail, because insufficient joint width causes spalling and cracking as the frame deflects.
Soft joints at masonry-to-frame connections are often incorrectly filled with mortar by the mason, who treats every joint as a mortar joint by default. A compressible filler (closed-cell foam backer rod with sealant over, or pre-formed expansion joint material) must occupy the designed soft joint. Mortar in a soft joint eliminates the movement capacity and defeats the purpose of the detail. Inspect soft joint locations at each masonry pour cycle before the work is concealed.
ACI 530.1 Section 3.3A (ties to structural frames); TMS 402 Section 7.3 (lateral support for masonry walls); IBC Section 2104.1.3; BIA Technical Notes 18A (movement joints in masonry).
Specifying mortar type at a soft joint location on the inspection report without noting that the joint should be filled with compressible material, not mortar. If the inspection report records 'Type S mortar at column interface' without flagging it as a non-conformance, the non-conformance has been implicitly accepted.
Masonry inspection records, nonconformance management, and completing the special inspection documentation.
Inspection Reports and Nonconformance Management
Masonry inspection reports must document what was inspected, when, and what was found. Because masonry inspection is typically continuous during grout placement and periodic during laying, the reports must reflect both types of inspection activity with appropriate detail. A grout pour inspection report should document the pour location, the grout slump measured, the lift heights observed, the consolidation method verified, and any samples taken. A daily laying inspection report should document the wall areas observed, the mortar mixing and proportioning verified, and any nonconformances noted.
End-of-day inspection report compilation: (1) Review field notes from the day's inspection activities. (2) Record all areas inspected with location references - grid lines, wall designations, or elevation. (3) Document all measurements taken - joint thickness, plumb readings, bar spacing, slump values. (4) Record material lot numbers and certifications verified. (5) List all tests performed - prism fabrication, grout sampling - with sample identification numbers. (6) Document all nonconformances, notifications made, and corrective actions taken or required. (7) Sign and date the report.
During a grout pour inspection at a reinforced CMU shear wall, the inspector notices that the contractor is placing grout using a bucket rather than a pump, and is not vibrating the grout after placement. The inspector stops the pour and notifies the foreman that TMS 602 requires mechanical consolidation. The foreman argues that the high slump will self-consolidate. The inspector documents the dispute and immediately contacts the engineer of record by phone. The engineer confirms that vibration is required and specifies the vibrator equipment requirements. The contractor obtains a vibrator and the pour resumes under proper consolidation. The inspector documents the interruption, the notification, the engineer's direction, and the correction in the daily report.
The masonry special inspection report package submitted at project close-out should include: all daily inspection reports organized chronologically, grout and prism test laboratory reports, masonry unit and material certifications, the record of any nonconformances and their dispositions, and the final compliance statement. This package is submitted to the building official and demonstrates that the required inspections were performed and that the masonry was constructed in conformance with the approved documents.
Inspectors sometimes fail to document inspection activities that showed no problems, reasoning that negative findings require no record. This is incorrect - the absence of a record that an area was inspected can later be interpreted as evidence that it was not inspected at all. Every inspection visit should produce a report entry, even if the entry simply confirms that the work in a particular area was observed and found to comply.
Masonry Inspection Report Content and Sequencing
A masonry special inspection report must identify the inspection type (continuous or periodic), the areas of masonry inspected by floor and grid location, the activities observed (mortar mixing, unit placement, grout pour, prism construction), the materials verified (CMU lot number, mortar batch, grout mix design), and any non-conformances with their disposition. For continuous inspection, the report must document every grout pour event with the mix design, temperature, slump, and lift height. Reports must be submitted to the project engineer and building official as required by IBC Section 1704.5.
Required masonry inspection report elements per IBC 1704.5: Project name, address, permit number. Inspector name and certification number. Date(s) of inspection. Area and activity inspected. Materials verified (lot/batch numbers). Test results (mortar samples, prism IDs). Grout pour log: mix design, temperature, slump, lift height, cell locations poured. Non-conformances found and status. Inspector signature and seal (if required by jurisdiction).
IBC Section 1704.5; IBC Section 1705.4 (masonry special inspection); ACI 530.1 Section 1.5 (submittal and inspection records).
Submitting weekly summary reports without daily grout pour logs. If a grout pour occurs on Tuesday and the weekly report is submitted Friday, the grout pour details (slump, temperature, lift height) are often lost or generalized. Daily grout pour records must be created on the pour date, not reconstructed from memory.
Non-Conformance Resolution and Certificate of Compliance
At project close-out, the special inspection agency issues a Statement of Special Inspections completion certificate confirming that all required inspections were performed, all non-conformances were resolved per EOR direction, and the work substantially conforms to the approved construction documents. This certificate is required by the building official for Certificate of Occupancy issuance. The inspector must retain all field inspection reports, test results, and non-conformance disposition letters for the retention period specified by the jurisdiction (typically 5 to 10 years after project completion).
A masonry project with early non-conformances (grout poured before inspector was present, wrong mortar type used for first 3 courses) that were corrected and documented creates no issue at close-out if the non-conformance log shows EOR review and acceptance of the corrective action. A project with late-discovered non-conformances that were never reported to the EOR creates a serious liability exposure for the inspection agency.
IBC Section 1704.5 (Statement of Special Inspections completion); IBC Section 109 (Certificate of Occupancy); ACI 530.1 Section 1.5C (completion statement).
Issuing the completion certificate before all pre-grout inspection hold points have been documented. Hold points (cell reinforcement inspection before grout pour) must be evidenced by inspection reports for every pour event. If a grout pour occurred without inspector presence and without advance notification to the inspector, that hold point cannot be retroactively certified.