NOTE Mortar and grout are the two cementitious binders of a masonry assembly, but they are not interchangeable: mortar is a stiff, low-water bedding material that bonds units face-to-face at the joints, while grout is a high-slump fluid placed into cores and cavities to bond reinforcement to the masonry and to develop composite structural action. (1.2.1)

NOTE The specified masonry compressive strength (f'm) is a property of the assembly, not of the mortar or grout alone. The structural engineer selects a mortar type and a grout strength together to achieve the required f'm under the prism or unit-strength method, so the mortar and grout requirements in this standard must be coordinated with the values shown on the structural drawings rather than chosen in isolation. (1.2.2)

NOTE Unit selection (concrete masonry units, brick, and structural clay tile) is specified under Unit Masonry, Concrete Masonry Units, and Brick Masonry; this standard addresses only the jointing and grouting materials placed between and within those units. (1.3)

NOTE Structural design and code compliance of the masonry assembly are governed by TMS 402 as adopted through IBC Chapter 21 and are shown on the structural drawings; this standard does not establish wall thickness, reinforcement, or f'm. (1.4)

NOTE Tile setting mortars and adhesives are governed by the ANSI A118 series and are outside the scope of this standard. (1.5)

NOTE Grout or adhesive for post-installed anchors is specified under Post Installed Anchors; non-shrink precision grout for base plates and equipment (ASTM C1107) and grout for post-tensioning are separate product categories not classified as ASTM C476 masonry grout and are not covered here. (1.6)

NOTE Many jurisdictions adopt TMS 402/602 by reference through the IBC; the base text of IBC 2021 references the 2016 edition, while the current published edition is 2022. Verify the edition adopted by the Authority Having Jurisdiction before fixing weather, lift-height, and consolidation requirements. (2.2.1)

NOTE ASTM C270 permits two mutually exclusive methods. The proportion specification prescribes the volumetric ratio of cement, lime, and sand and requires no preconstruction strength testing; it is the default and is appropriate for the great majority of projects. The property specification instead requires laboratory testing to demonstrate a minimum 28-day compressive strength and water retention, and is used where a documented strength is required or where unusual materials are proposed. The two methods shall never be specified simultaneously for the same mortar, because a mix proportioned to the property method will rarely satisfy the proportion table and vice versa. (4.1.1)

NOTE The proportion method controls quality through ingredient ratios rather than strength; applying a strength acceptance threshold to a proportion-specified mortar is inappropriate because the two methods are calibrated differently. (4.1.3)

NOTE Mortar color and joint texture vary with mix proportions, sand source, tooling, and curing, and these variations are not visible until a substantial area has been laid. A mockup establishes the accepted appearance and the workmanship standard before large areas are built, avoiding tear-out and acceptance disputes. (4.2.1)

NOTE The absorbent unit faces draw water from the grout and reproduce the in-place water-cement ratio that a nonabsorbent cylinder mold would not; this is why ASTM C1019 specifies the masonry-unit mold rather than a standard concrete cylinder. (4.4.2)

NOTE Cement hydration slows and can stop as temperature falls; mortar and grout placed cold without protection gain strength slowly, bond poorly, and are vulnerable to freezing before set, which permanently disrupts the paste. Conversely, high temperature and wind accelerate evaporation, stiffening mortar prematurely and reducing both workability and bond. The thresholds below establish when graduated protection becomes mandatory. (5.1.1)

NOTE Mortar type is not a quality ranking; it is a match to structural demand and exposure. Stronger mortar is also more rigid, and a mortar harder than the units it joins forces thermal and moisture movement to be relieved by cracking the (costly, irreplaceable) units rather than the (sacrificial, repointable) joints. The correct type is the lowest-strength mortar that satisfies the structural and exposure demand, not the strongest available. (6.1.1)

NOTE Mortar type strengths and typical applications are as follows. (6.1.2)

NOTE Portland cement-hydrated lime is the most compatible binder system: it develops the highest bond strength, tolerates a range of exposures, and contains no intentional air entrainment, making it suitable for reinforced and grouted masonry. (6.2.1)

NOTE Masonry cement is valued for workability, but the entrained air it carries reduces bond strength; this makes it unsuitable for reinforced and grouted applications without explicit engineering review. (6.2.3)

NOTE Mortar cement (ASTM C1329) is a pre-blended binder similar to masonry cement but with limited air entrainment and a verified minimum bond strength, making it acceptable for reinforced masonry where a pre-blended binder is preferred over field-batched portland cement-lime. (6.2.4)

NOTE The proportion-specification mixes below give the volumetric ratios of binder to lime to damp-loose sand for the common portland cement-lime and masonry cement mortars. Sand is measured in a damp, loose condition, which is the field-realistic state and the basis for the ASTM C270 proportion table. (6.8.1)

NOTE Pre-blended mortar is not a relaxation of the specification; the same strength, binder type, and proportion constraints apply regardless of whether the ingredients arrive pre-combined or are batched on site. (6.9.2)

NOTE Water retention is the mortar's ability to resist losing its mixing water to absorbent units; adequate retention keeps the mortar workable long enough to lay and tool the unit and lets cement hydration proceed rather than being starved of water at the bond line. (7.2.1)

NOTE Retempering replaces water lost to evaporation and is acceptable, but it must not be confused with adding water to mortar that has begun to set. Water added after the onset of set does not re-disperse the hydrating paste; it only raises the water-cement ratio and reduces strength. The single-retemper, two-hour rule draws the line between the two. (7.3.2)

NOTE Fine grout uses sand as its only aggregate and is selected for grout spaces less than 2 inches in least dimension or where close bar spacing would obstruct coarse aggregate. (8.1.1)

NOTE Coarse grout adds pea gravel to the sand and is selected for grout spaces 2 inches or greater in least dimension, where it is more economical than fine grout for filling larger voids. (8.1.2)

NOTE Self-consolidating grout is a high-flow product that fills and consolidates under its own weight without mechanical vibration; it is specified by compressive strength and slump-flow rather than by proportions, and requires clean, unobstructed cores because mortar fins or debris that conventional grout would be vibrated past can block its flow and leave undetected voids. (8.1.3)

NOTE Masonry grout (ASTM C476) is a high-slump, flowable mix in the 8 to 11 inch range, while non-shrink precision grout (ASTM C1107) is a low-slump dimensionally stable product for base plates and equipment. The two are not interchangeable, and stating "grout" without the governing standard generates immediate requests for information. (8.4.1)

NOTE The 2000 psi floor is the TMS 602 and ASTM C476 minimum, but the structural engineer frequently specifies 3000 psi or higher to raise the specified masonry compressive strength f'm of the grouted assembly; grout strength is one of the inputs to f'm. (9.1.2)

NOTE The high slump distinguishes masonry grout from concrete: the grout must be fluid enough to flow into and around reinforcement in narrow cores, and the absorbent masonry then draws off excess water to leave the in-place mix at a sound water-cement ratio. Reducing slump to concrete consistency would leave voids around the bars. (9.2.1)

NOTE The tooling profile is a weather-resistance decision, not only an aesthetic one. Concave and V-joints compress the mortar against the unit and shed water, so they are preferred for exterior exposure; flush, raked, and struck joints leave ledges or loosely compacted faces that hold water and reduce weather resistance, and raked joints in particular are inappropriate for severe exterior exposure. (10.2.1)

NOTE A pour is the full height of grout placed before construction resumes above it; a lift is the increment placed and consolidated as one operation within that pour. The limits below keep grout from segregating under its own head and ensure each increment can be consolidated before the next is placed. (11.1.1)

NOTE Vibration of a self-consolidating mix promotes segregation rather than consolidation, which is why mechanical vibration is prohibited for self-consolidating grout. (11.1.5)

NOTE Mortar fins and droppings accumulate at the base of grout spaces during laying. Without cleanout openings to inspect and clear the cell bottom before grouting, these obstructions trap voids at the most structurally critical location -- the base of the wall where flexural and shear demand on the reinforcement is greatest. (11.2.1)

NOTE Unlike mortar, grout is never retempered. Adding water to grout that has lost slump to initial set does not restore the mix; it raises the water-cement ratio and reduces the strength on which the assembly's f'm depends. (11.3.2)

NOTE Adhered veneer is bonded directly to a backing rather than supported on a shelf, so its setting mortar carries the unit in shear at the bond line. ANSI A118.4 latex-modified mortar is an alternative to ASTM C270 specifically for this condition, providing higher and more reliable bond than a conventional mortar where the veneer is thin and the backing is dense. (12.1.1)

NOTE Repointing existing masonry with a mortar harder than the original -- for example replacing a soft historic lime or Type O mortar with a modern Type S or M portland cement mortar -- is one of the most damaging errors in masonry repair. The hard new joint will not yield to thermal and moisture movement, so the movement is relieved by spalling the faces of the adjacent units, which are far costlier to replace than the joints. (13.1.1)

NOTE Cement and pre-blended dry mixes that absorb moisture in storage partially hydrate and lose strength even before mixing; lumpy or hardened material has already begun to set and cannot be salvaged by additional mixing. (14.3.2)

NOTE A low grout result at the base of a reinforced wall can indicate a void or a placement defect rather than a sampling anomaly, and statistical averaging conceals individual failures in the most structurally critical locations. (15.3.2)

NOTE Mortar and grout defects often appear only after a full seasonal cycle of thermal and moisture movement, so the warranty exists to cover failures that are not visible at substantial completion. Cracking caused by structural movement or by foundation settlement is a separate matter from mortar and grout workmanship and is governed by the structural provisions, not this warranty. (16.1.1)