The inquiry
A product standard—and a larger masonry system.
Concrete masonry units are among Florida’s most widely used building materials, but identifying the correct governing standard can be confusing. Florida Masonry received a Help Desk inquiry asking which standard applies to conventional concrete block used in Florida construction.
The questionWhat standard covers a concrete block in the Florida Building Code?
The expert answer
For conventional concrete masonry units—commonly called CMU or concrete block—the primary product standard is ASTM C90, Standard Specification for Loadbearing Concrete Masonry Units.
The currently effective 8th Edition (2023) Florida Building Code lists ASTM C90-16a in Chapter 35, Referenced Standards. Although its title refers to loadbearing units, ASTM C90-compliant concrete masonry units may be used in both loadbearing and nonloadbearing applications when appropriate for the project design.
What does ASTM C90 cover?
ASTM C90 establishes minimum requirements for the manufactured concrete masonry unit. Depending on the edition referenced by the applicable code and project documents, those requirements include:
- Permitted materials used to manufacture the unit
- Minimum compressive strength
- Unit dimensions and dimensional tolerances
- Face-shell and web configuration
- Maximum water absorption and density classification
- Appearance, finish, sampling, and compliance criteria
In practical terms, specifying ASTM C90 helps establish that block delivered to the project meets recognized minimum requirements for structural concrete masonry units. Manufacturer certifications and test reports may document compliance. Units are commonly sampled and tested using ASTM C140/C140M.
Does ASTM C90 cover the entire wall?
No. ASTM C90 is primarily a product standard for the concrete masonry unit itself. It does not establish every requirement for designing and constructing the completed masonry wall.
The Florida Building Code also adopts masonry design and construction provisions from TMS 402, Building Code Requirements for Masonry Structures, and TMS 602, Specification for Masonry Structures. These address the completed system, including structural design, reinforcement, grout placement, mortar, connections, construction tolerances, and quality assurance.
What belongs in the project specifications?
Specifications for structural concrete masonry units should clearly require compliance with the ASTM C90 edition recognized by the applicable code and contract documents. The design professional should also identify project-specific requirements such as unit size and configuration, required masonry compressive strength, density, architectural finish, fire resistance, energy performance, exposure conditions, and manufacturer documentation.
Simply stating “standard concrete block” may not provide enough information for bidding, manufacturing, submittal review, or field verification. A unit may comply with ASTM C90 and still be unsuitable if its strength, configuration, density, appearance, or other characteristics do not match the construction documents.
A note about ASTM editions
ASTM standards are updated periodically. A newer version may differ from the edition specifically referenced by the Florida Building Code. Always confirm the governing requirements for the project’s permit date, applicable code edition, and contract documents.
Key takeaways
ASTM C90 is the primary product standard for conventional structural concrete masonry units.
The 8th Edition (2023) Florida Building Code references ASTM C90-16a.
ASTM C90 governs the manufactured block—not every component of the completed masonry wall.
TMS 402 and TMS 602 govern important aspects of masonry design and construction.
Project specifications should identify both code-required compliance and additional project-specific unit requirements.
Florida Masonry Note
The applicable standard depends on what is being evaluated. ASTM C90 applies to the concrete masonry unit, while the Florida Building Code, TMS 402/602, and other referenced standards govern the design, materials, and construction of the complete masonry assembly. Always verify the code and referenced-standard editions applicable to the specific project.