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Concrete masonry units are available in a wide variety of sizes and shapes. (Photo from masonry is used to build structures that are economical, fire-resistant, and involve minimal maintenance. The most prevalent concrete masonry unit, also known as CMU, block, or cinder block, is a standard rectangular unit measuring 8 by 8 by 16 in. (200 by 200 by 400 mm) with cores. CMU are held together with mortar joints in most building applications.

CMU have been manufactured for more than 120 years, and consist primarily of portland cement, gravel, sand, and water. The concrete may also contain an air-entraining agent, color pigment, or water repellent. During the manufacturing process, a machine molds moist, low-slump concrete into the desired shapes. The CMU are then subjected to an accelerated curing process at elevated temperatures inside a special chamber. This is generally followed by a storage or drying period to help reduce the moisture content before shipment.



Glazed concrete masonry

Glazed concrete masonry

Concrete masonry is widely used to construct large and small structures in all regions of the world. The most common applications are:

  • Walls (loadbearing and nonloadbearing, exterior, interior, party, fire, separation, security, and veneer)
  • Retaining walls and ornamental garden walls
  • Highway sound barriers
  • Chimneys and fireplaces
  • Fire-safe enclosures of stairwells
  • Elevator shafts
  • Storage vaults
  • Piers, pilasters, columns
  • Bond beams, lintels, sills
  • Slope protection, paving, and grid pavers
Split-face concrete masonry
Split-face concrete masonry
CMU can be manufactured for a variety of architectural or structural functions. Split-face units are fractured lengthwise to produce an attractive, rough stone-like texture. The split face exposes the aggregates in the plane of fracture. A patented slotted unit provides high sound absorption for use in gymnasiums, factories, bowling alleys, or theaters where sound control is desirable. Glazed units are used in swimming pools and showers where sanitation and moisture resistance are needed.
Masonry is chosen due to its attributes:

  • Attractive appearance and versatility
  • Minimal maintenance
  • Long life and resistance to damage from moisture, weathering, and vandalism
  • Resistance to fire, wind, and earthquake
  • Economic installation
  • Sound attenuation
  • Energy savings due to thermal mass
Lightweight concrete masonry units, using lightweight aggregates, are up to 25% lighter than traditional masonry units. Lightweight CMU can speed installation by substantially increasing the number of units per hour that a mason can lay. They also offer increased fire resistance and energy benefits.


Concrete masonry has many environmental benefits during construction and for the life of the structure. See associated sustainability solutions and technical briefs (right) for more detail.
Durability.  Masonry provides a strong and durable structure, withstanding both routine natural wear as well as extraordinary impacts of natural and human disasters.
Energy efficiency. Because the thermal mass in CMU evens out daily temperature swings and because of their moisture resistance, concrete masonry homes have been most popular in the southern regions of the U.S. where buildings are subject to significantly warm and humid climatic conditions. Nonetheless, though the results may be less dramatic, the significant benefits of thermal mass can be experienced in most climatic regions in the U.S. May contribute to LEED Credit EA 1.

Indoor Environmental Quality. CMUs offer acoustical comfort and help safeguard indoor air quality due to their moisture resistance.

Recycled Content. CMU are frequently manufactured with recycled content. Fly ash, slag cement, or silica fume can substitute partially for cement, and recycled aggregates can replace newly mined gravel. Recycled content can contribute to LEED Credit M 4.


The CMU are joined together by mortar made from a binder consisting of one or more cements for masonry, sand, and water. Portland cement plaster, or stucco, is made from the same material as mortars and is sometimes considered to be a masonry product as well.

Mortarless units are "dry-stacked" and are generally held together by a coat of bonding plaster inside and out. These continuous surfaces hold the wall together, act as a barrier to moisture penetration, and provide an economical interior and/or exterior finish. If a conventional finish is preferred, gypsum wallboard and siding can be applied.
To find local manufacturers, check the National Concrete Masonry Association members directory.
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Located at Bookstore2005 ASHRAE Handbook - Fundamentals (2005)
The 2005 volume of the ASHRAE Handbook covers basic principles and provides essential data for HVAC&R design. In all, the Fundamentals volume includes more than 1,000 pages and 40 chapters on a variety of HVAC&R topics, covering general engineering information, basic materials, load and energy calculations and duct and pipe design. Available for $155
Located at BookstoreBuilding Code Requirements and Specification for Masonry Structures and Related Commentaries (2005)
American Concrete Institute, American Society of Civil Engineers, and The Masonry Society. 236 pages. Item Code: LT292
Available for $100. (ACI 530-05/ASCE 5-05/TMS 402-05 and ACI 530.1-05/ASCE 6-05/TMS 602-05)This code covers the design and construction of masonry structures and is accompanied by specifications and commentaries. Design methods include empirical design, prescriptive method, and strength design.
Located at BookstoreConcrete Masonry Handbook for Architects, Engineers, Builders (1991)
W. Panarese, S. Kosmatka, and F. Randall, Fifth Edition, Portland Cement Association. Item Code: EB008
Available for $35. The fifth edition discusses fundamentals of concrete masonry construction. Includes general and detailed information on masonry units, mortar, reinforcement, and grout; properties of masonry walls; design and layout of walls; hot- and cold-weather construction; construction techniques; finishes for masonry, such as coatings, paint, stains, and plaster; various applications of masonry; design details; inspection and testing of masonry ingredients and construction; and inspection and maintenance of masonry buildings. Helps building professionals design and construct fire safe, durable, and economical concrete masonry structures.
Located at BookstoreConcrete: Sustainability and Life Cycle (2007)
Portland Cement Association. Item Code: SN3011
Available for download for free This report presents the results of the LCI of three concrete products: ready mixed concrete, concrete masonry, and precast concrete.
Located at BookstoreHVAC Sizing for Concrete Homes (2009)
Portland Cement Association. Item Code: CD044
Available for $60. This software provides an alternative means of estimating heating and cooling system capacities for single-family concrete homes. The software calculates the system capacities based on the house dimensions, construction materials, location (U.S. and Canada) and thermostat set point.
Located at BookstoreLife Cycle Assessment of a Concrete Masonry House Compared to a Wood Frame House (2002)
Medgar L. Marceau and Martha G. VanGeem, Portland Cement Association Item Code: SN 2572, 168 pages
Available for free download. This report is an update of Life Cycle Assessment of an Concrete Masonry House Compared to a Wood Frame House (Marceau and VanGeem 2002). It presents the results of an assessment of the environmental attributes of concrete construction compared to wood-framed construction. A life cycle assessment (LCA) was conducted on a house modeled with two types of exterior walls: a wood-framed wall and a CMU wall. The LCA was carried out according to the guidelines in International Standard ISO 14044, Environmental Management - Life Cycle Assessment - Requirements and Guidelines. The house was modeled in five cities, representing a range of U.S. climates: Lake Charles, Tucson, St. Louis, Denver, and Minneapolis. The 228-square meter (2450-square foot), two-story, single family house has four bedrooms and a two-car garage. The system boundary includes the inputs and outputs of energy, materials, and emissions to air, soil, and water from extraction of raw materials though construction, maintenance, and occupancy. The house energy use was modeled using DOE-2.1E and the life cycle impact assessment was modeled using SimaPro. The results show that for a given climate, the life cycle environmental impacts are similar for the wood and CMU houses. The most significant environmental impacts are not from construction materials but from the production of electricity and natural gas and the use of electricity and natural gas in the houses by the occupants.
Located at BookstoreMasonry Designers' Guide, Fourth Edition (2004)
Portland Cement Association. Item Code: LT305
Available for $105. This book is one of the most popular design and teaching resources related to masonry because it provides comprehensive coverage, extensive code references, and numerous practical examples.
Located at BookstoreMasonry Mortars (2004)
Portland Cement Association. Item Code: IS040
Available for $10. This document includes coverage of mortar properties and current masonry standards used in the United States and Canada. Discusses component materials, batching and mixing procedures, the use mortar in hot and cold weather, and special techniques of mortar production.
Located at BookstoreReview of Masonry Aspects of the World Trade Center Disaster (2001)
David T. Biggs, P.E., LT277
Available for $45. This report describes an investigation of the World Trade Center and surrounding buildings in New York City following the events of September 11, 2001. Based on the personal observations of a member of one of the investigative teams, which included people from the Federal Emergency Management Agency (FEMA) and the American Society of Civil Engineers (ASCE), masonry clad buildings appear to have performed extremely well. Published by The Masonry Society.
Located at BookstoreSound Transmission Loss Through Concrete and Concrete Masonry Wall (1978)
Albert Litvin and Harold W. Belliston, Portland Cement Association, Item Code RD066
Many building codes require minimum sound transmission loss values, expressed as sound transmission class (STC), of 45 to 50. Tests of sound transmission loss were made on 8-in.-thick (203-mm) concrete masonry walls and on 6- and 8-in.-thick (152- and 203-mm) cast concrete walls finished with materials intended to increase sound transmission loss. Using furring, acoustic insulation, and wallboard attachments, STC values up to 59 and 63 were obtained for the masonry and cast concrete walls, respectively. Selected STC values, reported by other investigators, for a variety of walls are included for reference.
Located at BookstoreStandard 90.1-2001 - Energy Standard for Buildings Except Low-Rise Residential Buildings (2001)
ASHRAE. ISBN/ISSN: 1041-2336
Available for $88 member, $110 non-member. Incorporates 34 new addenda covering a wide range of topics, as well as editorial changes and updates to the body of the standard. The new addenda contain information on minimum energy efficiency standards, building envelope requirements, zone isolation, floor, ceiling and roof insulation, and power allowance calculation.
Located at BookstoreSupplementary Cementing Materials for Use in Blended Cements (1996)
Portland Cement Association. Item Code: RD112
Available for $40. Provides information on using fly ash, slag, silica fume and natural pozzolans in the manufacturing of blended cements and the effects of these materials on cement and concrete. This report is also found on CD019 and DVD019.
Located at BookstoreSupplementary Cementing Materials For Use in Concrete (2002)
Michael Thomas and Michelle L. Wilson. Portland Cement Association. Item Code: CD038
Available for $35. The first of a series of interactive distance learning programs specifically designed for training individuals on cement and concrete technology. This fully-narrated CD provides an intense self-contained course on supplementary cementing materials (SCMs) and their impact on the durability, workability, economy, and sustainability of concrete.
Located at BookstoreThermal Mass Comparison of Wall Systems (2001)
Portland Cement Association. Item Code: CD026
Available for $35. This 49-page report provides the thermal performance of eleven different structural wall systems: concrete masonry, insulated cast-in-place, insulated concrete forms, and AAC as well as wood and steel frame. The results illustrate the benefits of thermal mass, depending on climatic conditions for most of North America.
Download DocumentModeling Energy Performance of Concrete Buildings for LEED-NC v2.1 EA Credit 1 (2005)
Marceau, Medgar L. and Martha G. VanGeem, Portland Cement Association. Item Code: SN2880, 54 pages
This project provides in-depth information on energy savings in mid-rise buildings due to additional thermal mass and for exceeding building envelope thermal performance requirements.
Download DocumentNew Standard for Calculating Fire Resistance (1998)
Masonry Today, Vol. 7, No. 2. Portland Cement Association. Item Code: PL373
Available for free. Fire Resistant Walls - Beyond the Ratings discusses fire resistance performance of masonry walls, highlighting the fact that masonry walls often out perform other wall systems having equivalent fire resistance ratings. "New Standard for Calculating Fire Resistance" describes provisions of the new joint ACI and TMS standard, ACI 216.1-97/TMS 0216.1-97.
Download DocumentSlag Cement LEED NC 2.1 Guide (2005)
Slag Cement Association
Available for free. This 17-page publication discusses how slag cement can help contribute to achieving 9 different points toward for LEED™-NC certification.
Download DocumentSound Transmission Loss Measurements Through 190 mm and 140 mm Blocks with Added Drywall (1990)
A.C.C. Warnock , National Reseach Council Canada, #IR-586, 32 pages
Available for free. This report presents the results of a series of sound transmission loss measurements carried out under contract for the Ontario Concrete Block Association. The test series was augmented for research purposes by measuring sound transmission losses at different stages in the construction and disassembly of the walls. The report that follows provides an analysis of the information obtained during the complete measurement series. Available as a free download at National Research Council of Canada's Institute for Research in Construction website.
Download DocumentSustainable Concrete Masonry
National Concrete Masonry Association, 4 pages
Available for free. The brochure provides an introduction to sustainability solutions for site work, indoor air quality, energy efficiency, materials resources and innovation
Download DocumentSustainable Manufacturing Fact Sheet: Tire Derived Fuel (2005)
Portland Cement Association. Item Code: IS325
Available for free. By utilizing a cement kiln's controlled combustion environment, scrap tires can be an environmentally-sound source of energy in the manufacture of cement. This fact sheet shows how the popularity of tire-derived fuel has increased over the past two decades and summarizes its environmental benefits.
Download DocumentTaking Shelter from the Storm, Building a Safe Room inside your House (2004)
FEMA. Publication Number 320
This is a guide to building safe rooms within houses in high risk weather area. It has information on how to assess, plan, and build a safe room.
Download DocumentTrial by Earthquake, Fire, and Wind (1996)
Masonry Today, Vol. 6, No. 1
Free to download. This issue focuses on masonry performance in natural disasters starting with an introductory article titled, "Trial by Earthquake, Fire, and investigations. "Standing Up to the Storm Requires Taking It from The Top Down" examines lessons from hurricanes Andrew and Opal. California urban-wildland fires are reviewed in "Urban-Wind." "Hurricane Opal's Impact on Masonry Structures" summarizes the TMS Disaster Investigation Team findings and "TMS Disaster Investigation Teams Stand Ready" explains how teams are sponsored, selected, and trained for Wildland Fires - the Case for Non-Combustible Construction." In addition, a case study of an award-winning residential project titled "Safe and Sound Home" and an article on "New ASTM Standards for Cements for Masonry and Plaster" are included.
Download DocumentWhat's Your IAQ I.Q.? (1999)
Environmental Council of Concrete Organizations, #2846
Architects, engineers, and builders are becoming more proactive in assuring the Indoor Air Quality (IAQ) of the buildings for which they are responsible. Concrete is the best building material for forestalling sick building syndrome. Concrete also reduces the outgassing of indoor air pollutants. Because concrete structures are more energy efficient, they lower emissions form furnaces. This document is available for free from Environmental Council of Concrete Organizations. To find this article: Follow the link provided, then click "catalog" and scroll half way down the page to find the article.
Located at External Web SiteAmerican Coal Ash Association (2006)
A website dealing with the use of coal ash in concrete products.
Located at External Web SiteConcrete Homes
Portland Cement Association
A web resource for general information on concrete homes.
Located at External Web SiteLEED and Concrete Masonry Powerpoint
The National Concrete Masonry Association
Call The National Concrete Masonry Association Technical Inquiry Response at 703-713-1900 for a copy of this presentation.
Located at External Web SiteLEED Case Studies
The National Concrete Masonry Association
Various industry case studies highlighting concrete masonry's contributions for sustainability. Call The National Concrete Masonry Association Technical Inquiry Response at 703-713-1900 for copies of these case studies.
Located at External Web SiteMasonry Designs Magazine - Sustainability Issue (2004)
National Concrete Masonry Assocaition, October, 2004
Issue focused on sustainable development. Call NCMA Technical Inquiry Response 703-713-1900
Located at External Web SiteNational Concrete Masonry Association (2006)
In industry resource website.
Located at External Web SiteSilica Fume Association (2006)
An industry association website.
Located at External Web SiteSlag Cement Association (2006)
An industry resource website dealing with slag cement.