Codes & Standards

AAC Building Codes and ASTM Standards in the US

Architects, engineers and code officials who meet autoclaved aerated concrete (AAC) for the first time usually ask the same question: which code covers it? The answer has three layers, material standards, a design standard and the model building codes, tied together by an ICC-ES evaluation report. This guide walks through each layer using the two reports that cover the AAC supplied by MHE Group.

Short Answer

AAC is a recognized masonry material in the United States. The material is specified to ASTM C1693 (AAC) and ASTM C1694 (reinforced AAC elements), designed under TMS 402/ACI 530/ASCE 5 (Building Code Requirements for Masonry Structures, which has a dedicated AAC appendix), and adopted through the International Building Code and International Residential Code. For a particular product, the ICC-ES evaluation report is the document that confirms all of this for a building official: ESR-4740 for the blocks and ESR-1652 for the reinforced panels supplied by MHE Group.

Layer 1: ASTM Standards for the Material

The standards cited in the two evaluation reports, and what each one covers:

  • ASTM C1693: the material specification for autoclaved aerated concrete, with strength classes and density designations.
  • ASTM C1386: the earlier specification for precast AAC wall construction units, still referenced in the reports alongside C1693.
  • ASTM C1694 (and its predecessor C1452): reinforced AAC elements, the factory-reinforced floor, roof, wall and cladding panels.
  • ASTM C270: mortar for unit masonry; the thin-bed mortar used with AAC blocks is evaluated against the AAC thin-bed requirements.
  • ASTM A82: the plain steel wire used as reinforcement inside the panels.
  • ASTM E119: the standard fire test behind the hourly fire-resistance ratings.
  • ASTM E136: the noncombustibility test that classifies AAC as a non-combustible material.
  • ASTM C518: the heat-flow test behind the thermal conductivity values.

Layer 2: The Design Standard

Structural design of AAC masonry follows TMS 402/ACI 530/ASCE 5, the same standard used for concrete and clay masonry, through its appendix for AAC masonry. Loads come from ASCE 7. Two design conditions in the evaluation reports are worth knowing before a project starts: ESR-4740 limits AAC standard blocks in concrete masonry wall systems to Seismic Design Category A or B, and ESR-1652 treats cladding and wall panels as nonbearing units designed to resist wind loads, with floor and roof panels designed within the span and deflection limits given in the report. See AAC load-bearing systems for how the walls carry load.

Layer 3: Building Codes

The model codes do not describe AAC product by product; they adopt the design standard and accept evaluation reports. The current reports name the editions they were evaluated against: ESR-4740 the 2018 and 2009 International Building Code and International Residential Code, and ESR-1652 the 2012 editions. Under IBC Section 104.11, a building official may accept an alternative material when a valid evaluation report shows it meets the intent of the code, which is how AAC projects are routinely approved in jurisdictions that have adopted later editions. Always confirm the edition your jurisdiction has adopted and check that the report is current; ICC-ES reports carry an expiry date and are re-examined periodically.

Florida adds its own layer. The Florida supplement to ESR-4740 states that the blocks and thin-bed mortar comply with the 2020 Florida Building Code, Building and Residential, and with the High-Velocity Hurricane Zone provisions on the condition that exterior AAC walls are a minimum nominal 8 inches thick and built in accordance with Chapter 21 of the code.

What an ICC-ES Evaluation Report Gives You

An ESR is written for the code official and the specifier. For AAC it contains the strength class and density of the product, the design values (compressive strength, modulus, thermal conductivity, dead weight), the fire-resistance ratings and the assembly conditions behind them, the installation requirements (running bond, thin-bed mortar, grouting of cores and bond beams), the seismic and structural conditions of use, and the quality-control program at the plant. Citing the report number on the drawings and attaching it to the submittal usually answers the code review in one step.

Using the Reports in a Submittal

  • Identify the product and the report: ESR-4740 for standard blocks and thin-bed mortar, ESR-1652 for reinforced panels.
  • Check the code edition adopted by the jurisdiction against the editions named in the report, and the report's expiry date.
  • Design the walls under TMS 402 with the values from the report, and confirm the Seismic Design Category for the site.
  • Match the fire-rated assemblies to the ratings in the report: 6-inch blocks for a 4-hour wall, panel ratings as listed in ESR-1652.
  • Follow the conditions of use in the installation details: bond pattern, mortar, reinforcement and grouting.
  • In Florida, apply the Florida supplement and the 8-inch HVHZ condition where it applies.

The tables from both reports are reproduced on the AAC blocks and reinforced AAC panels pages, and the original PDFs are linked from technical downloads.

Related Knowledge Center Topics

See fire-resistant wall systems, building materials for hurricane-prone areas and what is AAC. Our AIA course on AAC structural systems covers the design side in more depth.

Related Services

Preparing a code submittal with AAC?

Send us the jurisdiction, the code edition and the wall types. We will confirm the applicable report, the design values and the fire-rated assemblies, and provide a quote.

Request a Quote

Frequently Asked Questions

Is AAC approved under the International Building Code?

Yes. The IBC and IRC recognize AAC masonry through the masonry design standard TMS 402/ACI 530/ASCE 5, which has a dedicated appendix for AAC. For a specific product, the ICC-ES evaluation report is the document a building official uses: ESR-4740 for the AAC blocks and ESR-1652 for the reinforced panels supplied by MHE Group, both available on our technical downloads page.

What is the difference between ASTM C1693 and ASTM C1694?

ASTM C1693 is the material specification for autoclaved aerated concrete itself: strength classes, density and physical properties. ASTM C1694 covers reinforced AAC elements, the factory-reinforced floor, roof and wall panels. Blocks are specified to C1693; panels to C1694.

Does the AAC supplied by MHE Group have ICC-ES evaluation reports?

Yes. The products are produced at our associated AERCON plant in Haines City, Florida, and are covered by ICC-ES ESR-4740 (standard blocks and thin-bed mortar) and ESR-1652 (reinforced floor, roof, wall, cladding and partition panels). Both reports are public documents.

Is AAC accepted in the Florida High-Velocity Hurricane Zone?

The Florida Building Code supplement to ESR-4740 states that the AAC standard blocks and thin-bed mortar comply with the HVHZ provisions on the condition that exterior AAC walls are a minimum nominal 8 inches thick and are constructed in accordance with Chapter 21 of the Florida Building Code. See building materials for hurricane-prone areas.