Only specify that the CMU meet all the requirements of ASTM C90, along with color and texture. Leave the weight and method of verifying compliance with the design strength (ƒ’ₘ ) (Unit Strength or Prism method) to the Structural Sheets.
*Medium weight concrete masonry units are the most commonly specified and constructed units in the Northwest
When Unit Strength method is used to verify ƒ‘ₘ suggest that the structural engineer use a “standard” composite masonry strength (e.g. 2,000psi, 2,250psi, 2,500psi, 2,750psi or 3,000psi) listed in the Unit Strength Table.
Remove “Grade” or “Type” from your concrete masonry specification. “Grade” or “Type” of masonry units are reserved for masonry veneers and do not correspond to a concrete masonry unit.
Table 2: Compressive Strength of Masonry based on the Compressive Strength of Concrete Masonry Units and Type of Mortar Used in Construction
Net area compressive strength of concrete masonry, psi (MPa)¹
Net area compressive stength of ASTM C90 concrete masonry units, psi (PMa)
Type M or S mortar
Type N mortar
1,750 (12.07)
—
2,000 (13.79)
2,000 (13.79)
2,000 (13.79)
2,650 (18.27)
2,250 (15.51)
2,600 (17.93)
3,400 (23.44)
2,500 (17.24)
3,250 (22.41)
4,350 (28.96)
2,750 (18.96)
3,900 (26.89)
—-
3,000 (20.69)
4,500 (31.03)
—-
¹ For units of less than 4 in. (102mm) nominal height, use 85% of the values Listed
TMS 602-16 Compressive Strengths for Concrete Masonry (Unit Strength Table for TMS 602-16)
Specifying Masonry Mortar
Only specify that the masonry mortar meets the requirements of ASTM C270 and any color that may be required. Leave the mortar Type (M, S, or N) to the Structural Sheets.
Do not specify a mortar strength. Mortar meeting the requirements of ASTM C270 may be either proportioned as shown in the C270 Proportion Table, or meet the physical properties required for the Type specified (i.e. compressive strength). Mortar should never be specified to meet both the proportion and property requirements.
Do not specify field testing in an effort to verify compressive strength of mortar used in the field. Field testing may be used to establish consistency in mortar used in the field. When field mortar testing is required, mortar must be sampled and tested prior to start of construction in accordance with ASTM C780 to establish a baseline for comparison of field-tested mortar. There are no ASTM requirements that field sampled mortar meet the strength requirements.
Mortar Joints
Specify that mortar joints should be tooled to form a waterproof joint and a tight bond with the CMUs. A concave tooled joint is most commonly used. Other acceptable weather resistant joints may also be specified, such as V or weathered joint.
Any mortar joints that are cracked or not bonded with the face shells of the CMUs should be removed and joints repointed prior to grout placement.
Specifying Masonry Grout
Specify that the masonry grout must meet the requirements of ASTM C476. Leave the strength requirements to the Structural Sheets. Insist that the mix design submitted indicates compliance with ASTM C476.
Masonry grout should have a slump between 8 and 11 inches for conventional grout. Self-consolidating grout meets the material requirements in ASTM 476. Because this mix is highly fluid, this material is qualified by measuring its slump flow and VSI using ASTM C1611.
Where possible, indicate Type 1-2 may be replaced with Type 1L cement. The total weight of cementitious materials in the mix may be replaced with up to 40% fly ash or a combination of 70% fly ash and ground granulated blast-furnace slag (contact nwcma.org for details).
Masonry grout should not contain integral water repellants.
Construction Tolerances
Construction tolerances should be specified to meet the requirements of TMS 602 Article 3.3F. Note that construction tolerances are intentionally compatible with material manufacturing tolerances.
Quality Control and Testing Program
A quality control and testing program should be specified to meet the requirements of TMS 602 Article 1.6.
Inspection and testing frequency should be outlined on the Structural Sheets. Incorporate Tables 3 and 4 from TMS 602 Article 1.6. We suggest creating a table similar to Tables 3 and 4 and indicate project specific tests and inspections and their frequency.
Movement and Control Joints
Movement and control joints should be specified and located on the project documents by the design team. Movement and control joint locations should never be left to the discretion of the contractor. A generic note on the Structural Sheets is not enough to comply with this requirement.
Concrete masonry (CMU) construction scores very well in comparison to alternative materials when considering these important factors.
Some of these include:
Fire- safety
Maintenance costs
Energy efficiency
Speed of construction
Resilience and Sustainability
Structural capacity
Durability
Design aesthetics
Product availability
Security
Since masonry buildings are built to last 50-75 years(or more) it is often assumed that they are much more expensive to construct. This construction cost study was conducted to develop realistic exterior wall cost estimates for two typical commercial building types designed with four different wall systems.
Construction material prices have been on a rising trend over the past few years with some recent slowdown. The 2023 Construction Cost Trends report by Gordian states that 82.5% of construction materials in the RSMeans database have experienced a significant cost increase since 2020. Going forward higher material prices are expected to stay. According to the AGC 2023 Construction Outlook Survey 73% of respondents are concerned about material costs and 63% about construction delays due to material availability issues. We believe this is an opportune time to conduct this study. The cost estimates were developed for three northwest metropolitan areas including Portland, Seattle, and Spokane.
OUR TEAM Our consultant team was comprised of the following construction industry professionals.
Roger Roen and Chris Collins, Roen Associates, Spokane, WA. Doug Mitchell, MMEC Architecture, Spokane, WA Tristan Burton, Structural Forte, Inc., Spokane, WA
BUILDINGS
Two prototype buildings were designed to meet both the structural and energy code requirements of the Oregon and Washington state codes. The buildings selected are both single-story, tall wall structures. TYPE 1 is a 35,200 sf building with 28’-8” high walls. It represents building occupancies such as retail, storage, fitness/recreation, manufacturing, assembly, etc. The plan dimensions are 160’ x 220’. TYPE 2 is a 5,820 sf building with 31’-4” high walls. It primarily represents a school or health-club gymnasium. The plan dimensions are 60’ x 97’.
Each building was designed with four different exterior wall systems, one with two cladding options. For comparison purposes all the other elements of the building were unchanged unless required by design. The buildings were each sited in the same three northwest areas mentioned previously. Cost estimates were developed for the complete exterior wall systems, including footings/foundations, designed to resist gravity and lateral loads. The concrete slab, roof system, and any interior columns required were assumed to be the same for each exterior wall option for each building type and were not included in the total cost estimates.
NOTES
The single-wythe, integral-insulated concrete masonry wall complies with the mass wall exception of the Oregon and Washington energy codes for similar building types. The CLT wall was designed to have wood exposed on the building interior rather than cover it for fire resistance. The steel frame/metal-stud wall includes the cost of perimeter steel beams, columns, and brace frames within the wall for required structural capacity.
Exterior Wall Systems
Sketches of the four wall systems compared are shown below along with descriptions of their composition.
Structural Concrete
•Colored split-face CMU (8” or 10” wide) • Reinforcement/grout •Injected foam insulation •Exterior water repellant
Structural Steel/Metal Stud with Metal Panels •GWB interior •Metal studs at 16” o.c. with batt insulation • Sheathing •2” rigid insulation •WRB •RC channels •Metal panel finish (20 ga.)
Structural Steel/ Metal stud with Brick Veneer
Same assembly as described on the left except metal panel finish replaced with standard size brick veneer.
The total estimated wall system costs for the two building types studied are shown in Tables #1-6. The estimates cover the initial costs of construction including material, labor, and equipment. Shown in the Figure1 graph is the average cost-ratio for exterior wall system options relative to the least expensive concrete masonry choice. The integral-insulated CMU wall serves as the baseline with a ratio of 1.0. These cost-ratios indicate the level of cost increase above the concrete masonry baseline wall for the two building types studied. An interior wall insulated/gypsum board finish CMU option is included for projects where the mass wall exception does not apply. For ease of exterior wall comparison, Table 7 provides the estimated northwest average cost per square foot of opaque wall area for the different options studied.
SUMMARY For the two building types analyzed in this study, constructing them with structural concrete masonry walls is the least costly option. For the Type 1 building, constructing it with any of the alternative wall systems increased the initial cost from 37 to 167 percent depending upon wall type and location. For the Type 2 building, constructing it with anything other than integral-insulated CMU increased the initial cost similar percentages. This finding is also true even when interior wall insulation with gypsum board finish is added to the structural CMU wall. The values in Figure 1 present this same cost information in a different manner.
Comparing the steel frame structure with various cladding options is interesting. The standard-size brick veneer is only $3/sf (4%) more than architectural metal panel cladding. If larger size brick or CMU veneer is selected, the masonry veneer option becomes a less expensive finish than the metal panels. Additionally, a classic brick/structural block masonry cavity wall, often referred to as the “perfect wall”, is cost competitive with the steel frame system. And masonry products are readily available and normally locally produced.
Results of the construction cost study are shown in the tables. They are listed by building type, location, and wall assembly.
Table1: Building Type1, 35,200 sf, Portland, OR
Extrior Wall Assembly
Total Estimated Cost
Structural 8″ CMU
$1,508,214
Steel Frame- Metal Panel
$1,944,555
Steel Frame- Brick Veneer
$2,091,697
CLT- 9.625″
$2,752,263
6″ Concrete Tilt-up
$1,554,564
Table 2: Building Type 1, 35,200 sf, Seattle WA
Extrior Wall Assembly
Total Estimated Cost
Structural 10″ CMU
$1,176,139
Steel Frame- Metal Panel
$1,996,778
Steel Frame- Brick Veneer
$2,104,147
CLT- 9.625″
$2,754,671
8″ Concrete Tilt-up
$1,607,599
Table 3 : Building Type 1, 35,200 sf, Spokane WA
Extrior Wall Assembly
Total Estimated Cost
Structural 8″ CMU
$976,225
Steel Frame- Metal Panel
$1,795,066
Steel Frame- Brick Veneer
$1,903,648
CLT- 9.625″
$2,605,984
6″ Concrete Tilt-up
$1,539,564
Table 4 : Building Type 2, 5,820 sf, Portland, OR
Extrior Wall Assembly
Total Estimated Cost
Structural 10″ CMU
$462,075
Steel Frame- Metal Panel
$858,228
Steel Frame- Brick Veneer
$950,358
CLT- 12.375″
$1,205,507
8″ Concrete Tilt-up
$641,332
Table 5 : Building Type 2, 5,820 sf, Seattle, WA
Extrior Wall Assembly
Total Estimated Cost
Structural 10″ CMU
$478,894
Steel Frame- Metal Panel
$879,518
Steel Frame- Brick Veneer
$965,200
CLT- 12.375″
$1,231,071
8″ & 10″ Concrete Tilt-up
$663,018
Table 6 : Building Type 2, 5,820 sf, Spokane, WA
Extrior Wall Assembly
Total Estimated Cost
Structural 10″ CMU
$425,718
Steel Frame- Metal Panel
$805,861
Steel Frame- Brick Veneer
$845,319
CLT- 12.375″
$1,149,425
8″ & 10″ Concrete Tilt-up
$635,461
Figure 1: Northwest Wall Systems Average Cost-Ratio
(Compared to Integral-Insulated Concrete Construction)
Masonry construction offers a high degree of design flexibility with numerous combinations of product color, texture, size/shape, and pattern. Table 8 provides additional masonry cost information for some of these design options. It can be used in combination with Table 7 to budget wall costs.
As stated by a local architect, “The range of masonry products available provides unparalleled design flexibility, allowing masonry buildings to fit seamlessly into almost any architectural context”. This cost study demonstrates that masonry wall systems are very cost competitive with alternative systems for the construction of exterior walls in commercial buildings. In fact, for the two building types studied it was shown that structural concrete masonry walls are the lowest cost option. Additionally, the cost of brick veneer is competitive with architectural metal panels, and structural CMU backup walls are cost competitive with steel/metal-stud construction.
Combined with all the other benefits of masonry construction it makes good sense to spend your construction dollars on masonry wall systems for your next project.
Table 7: Exterior Wall Cost Estimates
(Northwest average $/SF of wall area)
Exterior Walls
$/SF of Wall Area
8″ Colored Split-Face CMU with Integral-Foam Insulation
$38
10″ Colored Split-Face CMU with Integral-Foam Insulation
$41
8″ Colored Split-Face CMU with Interior Wall Insulation/finish
$46
10″ Colored Split-Face CMU with Interior Wall Insulation/finish
$49
Steel Frame w/ Metal Panel
$73
Steel Frame w/ Standard Size Brick Veneer
$73
CLT (7-ply/alt)
$109
CLT (9-ply/alt)
$119
6″ Tilt-up Concrete
$62
8″ Tilt-up Concrete
$63
Standard Size Brick Veneer (running bond)
$41
Standard Brick/Structural Block Cavity Wall
$75
Table 8: Additional Masonry Options
The tables below provide wall cost differentials for other masonry design options based upon cost-study estimates. Masonry construction offers enhanced design flexibility with numerous product choices
Concrete Masonry
DESIGN OPTIONS
COST DIFFERENTIAL (Approximate $/SF of Wall Area)
12″ wide vs. 10″ wide CMU
+$3.00
Ground face vs. split face (colored CMU)
+$2.75
Natural gray vs. colored (split -face)
-$1.00
Natural gray smooth vs. colored split-face
-$3.00
Interior wall insulation/ gyp finish vs. injected foam insulation
+$7.50
DISCLAIMER
The cost estimates provided in this publication are based on the knowledge and experience of the cost study consultants who accept no liability for the use of this information. The estimates should only be used for project budgeting purposes by qualified individuals.
LIFE-CYCLE CONSIDERATIONS
Although initial construction cost is an important factor in the selection of construction assemblies for a building project, consideration should also be given to long-term costs and impacts. This is where masonry walls really shine with their high durability and low maintenance properties. Designed for a 50+ year life they are inherently highly resilient to natural and man- made disasters and sustainable. There is nothing more sustainable than constructing one 75-year building rather than three 25-year buildings. When life-cycle analyses are conducted considering the full life of a building or material from cradle to grave, masonry wall assemblies are typically determined to be the best choice for your building project.
Northwest Concrete Masonry Association (NWCMA) is pleased to announce that the Central Spokane YMCA/YWCA and Parkrose Middle School (Portland, OR) recently achieved the U.S. Resiliency Council (USRC) Silver Rating.
Parkrose Middle School (Portland, OR)
The USRC Building Rating System describes the expected impacts of an earthquake or other natural disaster on buildings. The Silver Rating indicates achievement of key performance targets including limited building damage and a shortened operational recovery time after a major seismic event. Most importantly, loss of life caused directly by building damage is not anticipated.
Tom Young, Executive Director of NWCMA, explains, “A resilient building is an asset to a community. In addition to being a good long-term investment it can often serve as a recovery operations center or provide shelter to a community impacted by a natural disaster.”
Central Spokane YMCA/YWCA (Spokane, WA)
The Parkrose Middle School is a two-story 140,000 sq. ft. structure designed by Dull Olson Weekes – IBI Group Architects, Inc. and KPFF Consulting Engineers. It is an excellent example of an all-masonry cavity wall system incorporating interior exposed concrete masonry structural walls with a brick veneer exterior. The school has also received several other design awards as well as LEED Gold status and is a huge source of pride within the community.
Parkrose Middle School (Portland, OR)
The Central Spokane YMCA/YWCA is a two-story load-bearing masonry building designed by ALSC Architects and Coffman Engineers. It utilizes both 8” and 12” concrete masonry shear walls. This was the first time the YMCA and YWCA combined resources into one facility which was designed to meet a silver LEED certification.
Central Spokane YMCA/YWCA (Spokane, WA)
Achieving the USRC Silver Rating recognizes the inherent resiliency of these reinforced masonry buildings which were the first two rated under the USRC Getting-to-Silver initiative. When a natural disaster such as an earthquake strikes, it is critical to have safe buildings that sustain minimal damage and quickly achieve functionality. Resilient buildings perform well and contribute to resilient communities.
Established in the 1950s, the Northwest Concrete Masonry Association (NWCMA) works to support its original goal of industry advancement by striving for more innovative and productive ways to design, deliver, and install concrete masonry wall systems.
NWCMA also works on behalf of the concrete masonry industry and designers in the Pacific Northwest to educate architects and engineers on the benefits of using concrete masonry in the design of their buildings.
Affiliation with NWCMA offers both professional growth and business opportunities. It provides its members and affiliates with comprehensive, dynamic services, which include expert technical assistance, education, marketing, and research and development.
For more information, call 425.655.0719 or visit www.nwcma.org.
We recently received a sobering reminder that our world has changed forever, and that fact has far-reaching implications for our industries that build our cities, towns, and the systems that sustain our way of life.
The National Climate Assessment report sums it up clearly. “The nation’s economy, security, and culture all depend on the resilience of urban infrastructure systems.”
In the Pacific Northwest catastrophic disasters from floods, wildfires, and periods of bitter cold will be the new realities driving the need for adaptation, notes the climate report.
A Pacific Northwest Building Resilience Coalition article co-authored by Bill Larson, CalPortland’s Vice-President for Marketing, notes this means we need to change how we build, what we build with, where we build, and we must ensure that our buildings and communities are more resilient, more efficient, and more livable.
These are profound challenges for industries already grappling with severe economic and social pressures.
The article points out that changing policies and planning measures such as building codes, zoning regulations, land-use plans, water supply management, green infrastructure initiatives, health care planning, and disaster mitigation efforts, are all actions that can support adaptation.
Integrating disaster preparedness and resiliency planning into on-going public policy processes is a low cost, no regrets approach that allows us to use existing funding sources for climate adaptation.
But to be successful, these adaptation efforts require that private sector players and governments must come together in common cause, notes Larson.
“Only by working together can we reduce our exposure to climate-related stresses and strengthen ability to adapt to changing conditions. We can do it. We must do it. There is too much at stake for inaction on our part.”
