ASTM C62 vs ASTM C216: Brick Standards Explained

ASTM C62 covers building brick: solid clay or shale units for structural and non-structural masonry where appearance is not a requirement. ASTM C216 covers facing brick, where appearance is a requirement. Both grade bricks by their resistance to freezing when wet. C62 has three grades, SW, MW and NW; C216 has SW and MW, and adds types FBS, FBX and FBA that control appearance and dimensional tolerances.

For a brick plant, the difference is practical. A plant making C62 building brick has to control strength and durability. A plant making C216 facing brick has to control the same properties and also size, distortion, chips and color, brick by brick. This guide sets out what each standard covers, the grades and types, the published limits, and what they mean for a plant that wants to sell into markets that specify ASTM. Numerical limits below are as summarized by the Brick Industry Association (BIA); ASTM revises these specifications regularly, so check the current edition before you design a product to them. Figures marked “on our reference lines” come from the fired clay brick lines YuxingCorp supplies.

ASTM C62 vs ASTM C216 at a Glance

Sources for the table: ASTM C62-23 and C216-26a scope pages; BIA Technical Note 9A (2007). “Solid” in ASTM means the net cross-sectional area is at least 75% of the gross area, so voids are at most 25% (BIA TN 9A). Units with more voids fall under ASTM C652 for hollow brick, and paving brick under ASTM C902.

What Each Standard Covers

ASTM C62 is the specification for ordinary building brick. Its scope covers brick for “both structural and nonstructural masonry where external appearance is not a requirement,” made from clay, shale or similar earthy materials, shaped by molding, pressing or extrusion and fired to develop strength and durability. It does not cover facing units, and it points buyers who care about appearance to C216 (ASTM C62-23).

ASTM C216 covers facing brick that supplies structural or facing components, or both. The 2026a edition notes that additives or recycled materials are permitted at the manufacturer’s option, and that the specification may not be used to qualify units made from other materials, by other forming methods or with other binding means (ASTM C216-26a scope).

Both standards apply their requirements at the time of purchase; testing brick taken out of existing walls is outside their intent (ASTM C62-23, C216-26a). Both list the same families of requirement: durability, absorption, freezing and thawing, breakage, cracking, weathering index, compressive strength and initial rate of absorption.

The Gulf standards body has adopted C216 directly. GSO ASTM C216:2025, approved in October 2025, is listed as the current GCC edition and is based on ASTM C216-24 (GSO). A plant selling facing brick into the Gulf may therefore be asked for C216 compliance under a GSO number, one edition behind the latest ASTM text.

Grades SW, MW and NW: Durability Requirements

The grade letters describe the weathering exposure: S for severe, M for moderate and N for negligible weathering (BIA TN 9A). Grade SW is intended for use where high and uniform resistance to cyclic freezing is desired, including brick that may freeze while saturated; Grade MW is for use where moderate resistance to cyclic freezing is permissible, for brick that may be damp but not saturated when it freezes (US NIH Technical Bulletin, citing ASTM C216). Grade NW, in C62 only, is typically confined to interior use or to places where the brick is protected from water absorption and freezing (BIA TN 9B).

The physical requirements, as summarized by the BIA in 2007:

MPa values are our conversions. Source: BIA TN 9A (2007), Table 4; check the current editions of C62 and C216.

Three alternatives let a brick qualify without meeting every column (BIA TN 9A):

1. Absorption alternate. The saturation coefficient limit does not apply if the cold-water absorption of no single brick in a random sample of five exceeds 8%.
2. Freezing and thawing alternative. The boiling absorption and saturation coefficient limits do not apply if five bricks pass the ASTM C67 freeze-thaw test with a weight loss not greater than 0.5% of dry weight for any brick (Grade SW).
3. Low weathering index alternative. Where the weathering index is less than 50, brick with an average compressive strength of at least 2,500 psi (17.2 MPa) qualify.

The saturation coefficient is the ratio of 24-hour cold-water absorption to 5-hour boiling absorption. A low ratio means part of the pore space stays empty in normal wetting, leaving room for ice. How these are tested is covered in our guide to clay brick testing methods.

Which Grade Fits Your Market

ASTM’s weathering index is based on freezing and winter rainfall. C62 and C216 include a map of approximate weathering indices for the United States (BIA TN 9B; MCAA), and the low weathering index alternative applies below an index of 50 (BIA TN 9A). Outside the United States, the climate still decides which grade is worth making:

• Gulf states and much of the Middle East. Freezing is rare. If the local specification allows the low weathering index alternative, strength rather than absorption usually governs. Confirm what the project specification and the municipality accept.
• Central Asia. Cold, freezing winters make freeze-thaw durability the property that matters for facades and exposed work. Aim for Grade SW and plan freeze-thaw testing.
• Southeast Asia and most of Africa. Freezing is rare except at altitude, but wetting is not. Absorption still matters for water penetration and efflorescence, even where the freeze-thaw grade does not.

In the United States, the BIA observes that “most manufacturers make brick to meet the designation for the most severe weathering exposure, SW,” so that they can ship anywhere (BIA TN 9B). For an export-oriented plant the same logic applies: if your clay and firing can reach SW, one product covers more markets.

Types FBS, FBX and FBA in ASTM C216

The type letters in C216 describe appearance and dimensional control: S for standard production, X for extreme or extra control, and A for architectural or aesthetic criteria that must be specified (BIA TN 9A).

• FBS is facing brick for general use.
• FBX is for general use where higher precision and more exact sizes are required.
• FBA is for architectural effects, with greater variation in size and texture (Masonry Advisory Council; Mason Contractors Association of America).

The types are enforced through three tables. Distortion limits, as reproduced by the BIA:

Source: BIA TN 9A (2007), Table 7; check the current edition of C216.

Dimensional tolerances are set by size band, tighter for FBX than for FBS. For chips, the first row of the C216 table as reproduced by the BIA requires at least 95% of FBX bricks to have chips no larger than 1/8 in. (3.2 mm) on edges and 1/4 in. (6.4 mm) on corners, against 90% of FBS bricks within 1/4 in. (6.4 mm) and 3/8 in. (9.5 mm). A delivery may also include up to 5% broken brick (BIA TN 9A, 2007). Check the full tables in the current edition before agreeing an acceptance procedure with a buyer.

Initial rate of absorption is not a qualifying property in C62 or C216; if the purchaser wants it reported, the test must be requested (BIA TN 9A). The specifications recommend a limit of 30 g/30 in.²/min (BIA Technical Note 39, a 2001 summary; check the current editions).

Hollow Brick: Where ASTM C652 Takes Over

Once voids exceed 25% of the gross area, the unit is no longer a C62 or C216 brick but a hollow brick under ASTM C652. C652 has two void classes, H40V (more than 25% and not more than 40%) and H60V (more than 40% and not more than 60%), the same SW and MW grades, and four types: HBS, HBX, HBA and HBB, the last for units where color, texture and uniformity do not matter, typically in unexposed locations (BIA Technical Note 41, 2008).

The BIA’s two summaries of the C652 grade limits do not fully agree: TN 41 (2008) gives 22.0% as the individual 5-hour boiling absorption limit for Grade SW, while TN 9A (2007) shows 20.0% across all three specifications. Read the current C652 edition itself before designing a hollow product to it. Our article on hollow clay bricks explains how the void pattern is produced.

What C62 and C216 Mean for a Brick Plant

ASTM does not fix brick sizes in C62 or C216; C216 describes facing brick as available “in a variety of sizes, textures, colors, and shapes.” A plant producing metric sizes can therefore still test against ASTM grades, as long as the buyer accepts the size and the tolerance band that applies to it. Typical products on our reference lines are standard bricks of 240 × 115 × 53 mm, perforated bricks of 240 × 115 × 90 mm and 270 × 130 × 118 mm, hollow blocks of 390 × 190 × 190 mm and 240 × 115 × 75 mm bricks for export markets. Only the solid sizes, with voids of 25% or less, fall under C62 or C216.

The properties ASTM grades on are set in the plant:

1. Compressive strength depends on the body, de-airing and firing. Two-stage vacuum extruders on our reference lines reach up to 4.0 MPa extrusion pressure and −0.092 MPa vacuum; see vacuum brick extruder.
2. Absorption and saturation coefficient track how far the body has vitrified, which is set by the firing range. Underfired bricks fail SW on absorption long before they fail on strength. See clay brick firing temperature.
3. Size, distortion and chips for C216 depend on die wear, drying and firing shrinkage, setting pattern and handling at unloading and packing.
4. Efflorescence depends on soluble salts in the raw material and fuel. If buyers will invoke “not effloresced,” test raw materials for sulfates early.

FAQ

What is the difference between ASTM C62 and ASTM C216?

ASTM C62 covers building brick for structural and non-structural masonry where appearance is not a requirement, in Grades SW, MW and NW. ASTM C216 covers facing brick where appearance matters, in Grades SW and MW, with types FBS, FBX and FBA that add limits on size, distortion and chips. Both use ASTM C67 test methods.

What does Grade SW mean for brick?

SW stands for severe weathering. It is the grade for brick that may freeze while saturated with water. As summarized by the BIA in 2007, it requires an average compressive strength of at least 3,000 psi (20.7 MPa), average 5-hour boiling absorption of no more than 17.0% and an average saturation coefficient of no more than 0.78; check the current edition.

What is the difference between FBS, FBX and FBA brick?

All three are ASTM C216 facing brick. FBS is standard facing brick for general use. FBX is for work that needs higher precision, with tighter limits on size and distortion. FBA is architectural brick with deliberately varied size and texture; its distortion limits are as specified by the purchaser.

Can Grade NW brick be used outside?

Grade NW exists only in ASTM C62 and has no absorption or saturation coefficient limits. The BIA notes that NW brick are typically confined to interior applications, or to places where the brick is protected from water absorption and freezing. For exposed exterior walls, specify MW or SW to suit the climate.

Which edition of ASTM C62 and C216 is current?

When this article was written, the ASTM store listed C62-23 and C216-26a as active. In the Gulf, GSO ASTM C216:2025 is based on C216-24. ASTM revises these specifications often, so check the current edition named in your contract or project specification before testing to it.

Planning a Fired Clay Brick Plant?

Strength, absorption and size are set by the extrusion, drying and firing configured on a fired clay brick production line. Tell us the standard and grade your market specifies when you send raw material samples, so that the test firing is judged against the right limits.

Sources

• ASTM International, ASTM C62-23 Standard Specification for Building Brick (Solid Masonry Units Made from Clay or Shale): https://store.astm.org/c0062-23.html
• ASTM International, ASTM C216-26a Standard Specification for Facing Brick (Solid Masonry Units Made from Clay or Shale): https://store.astm.org/c0216-26a.html
• GCC Standardization Organization, GSO ASTM C216:2025 Standard Specification for Facing Brick: https://www.gso.org.sa/store/standards/GSO:976714/GSO%20ASTM%20C216:2025?lang=en
• Brick Industry Association, Technical Note 9A: Specifications for and Classification of Brick (October 2007): https://www.gobrick.com/media/file/9a-specifications-for-and-classification-of-brick.pdf
• Brick Industry Association, Technical Note 9B: Manufacturing, Classification, and Selection of Brick, Selection, Part 3 (December 2003): https://www.gobrick.com/media/file/9b-manufacturing-classification-and-selection-of-brick-selection-part-3.pdf
• Brick Industry Association, Technical Note 41: Hollow Brick Masonry (January 2008): https://www.gobrick.com/media/file/41-hollow-brick-masonry.pdf
• Brick Industry Association, Technical Note 39: Testing for Engineered Brick Masonry – Brick and Mortar (November 2001): https://www.gobrick.com/media/file/39-testing-for-engineered-brick-masonry–brick-and-mortar.pdf
• US National Institutes of Health, Office of Research Facilities, The Freeze-Thaw Cycle in Concrete and Brick Assemblies, Technical Bulletin Issue 84 (January 2019): https://orf.od.nih.gov/TechnicalResources/Documents/Technical%20Bulletins/19TB/The%20Freeze-Thaw%20Cycle%20in%20Concrete%20and%20Brick%20Assemblies%20January%202019-Technical%20Bulletin_508.pdf
• Masonry Advisory Council, A Specification for Facing Brick (2023): https://masonryadvisorycouncil.org/wp-content/uploads/2023/10/A-Specification-for-Facing-Brick.pdf
• Mason Contractors Association of America, ASTM Standards for Brick: https://masoncontractors.org/technical-talks/astm-standards-for-brick/