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  1. 2 likes
    In accordance with ASTM C90, all non-split sides (typically the height and length of a unit) must comply with the ± 1/8 in. (3.2 mm) dimensional tolerance, however, the split face side of the unit is not held to this tolerance. Because the split surface is intended to show variability and irregularity, ASTM C90 waives the tolerance requirements for any split dimension
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    Self-consolidating grout is an engineered grout that is specially formulated to have good flow characteristics without segregation of constituent materials. It is important to note that it is not simply watered-down grout. Instead, it utilizes carefully controlled particle-size distribution and chemical admixtures to achieve stable flow characteristics. Unlike conventional masonry grout, self-consolidating grout does not require external consolidation when pouring. Since 2008, self-consolidating grout has been included as an acceptable material within TMS 602 (Specification for Masonry Structures) so it can be used in construction – subject to a few material testing considerations. For more information, see NCMA TEK Note 9-2B, see attached. Below is self-consolidating grout undergoing a slump test in accordance with ASTM C1611. TEK 09-02B.pdf
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    ASTM C90 is the governing ASTM standard that all concrete masonry manufacturers must ensure their products meet if their units are to be used in a load-bearing application. There are additional ASTM standards in regards to concrete masonry units depending upon their end use which are described in further detail in TEK Note 1-1F (see attached). ASTM standards contain the minimum requirements a product must attain to achieve the necessary properties for quality performance. The properties defined in these standards include compressive strength, absorption, density classification, face shell and web dimensions, permissible variations in dimensions, and finish/appearance criteria. The standards do not define the color or texture of the unit as these are defined by the purchaser. TEK 01-01F9.pdf
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    The main difference between Type M, S, and N mortar is the cement content in the mortar. From highest to lowest cement content, the order is Type M, Type S, and Type N. It is recommended to always use the weakest possible mortar on a wall system due to it being easier to work with for the mason, provides proper durability, and helps mitigate cracking in the assembly as the mortar cures. For more information on mortar, please refer to TEK Note 9-1 (see attached). TEK 09-01A.pdf
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    Very conditionally. In applications where the water will flow onto or impact the manufactured stone; I'd definitely recommend against such applications as the water will eventually erode the surface pigments...and eventually the stone. If, however, the manufactured stone is simply providing a backdrop to a waterfall without becoming wet due to the falling or splashing water, such applications may be acceptable. I would note that exterior waterfall applications such as this would require additional considerations to ensure the flowing water isn't diverted onto the surface of the stone by wind or other means.
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    How many layers of water resistant barrier (WRB) are required for manufactured stone veneer installations?
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    No. Article 3.2 C of TMS 602 specifically permits wet-cutting of CMU on site. One could argue that the process of wet-cutting introduces additional water thereby subsequently increasing the potential for shrinkage cracking, however, given that the affected unit(s) is relatively small - coupled with the fact that existing industry crack control recommendations assume that units are not 'dry' at the time of installation, the potential for increased shrinkage potential is insignificant. Additional information is provided by TMS 602 Article 3.2 C Commentary: 3.2 C. Wetting masonry units — Concrete masonry units increase in volume when wetted and shrink upon subsequent drying. Water introduced during wet cutting is localized and does not significantly affect the shrinkage potential of concrete masonry.
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    Additionally, because a split face unit is literally split from two or more units, the thickness of the split-side face shell can vary both outward and inward, thus, the face of the unit is typically thicker than a standard CMU unit, to allow for the inward portion of the split to still be greater than the minimum thickness allowed. (E.g. Some split face units are up to 1" wider than a standard unit, 9x8x16 vs 8x8x16).
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    How do I measure the dimensional tolerance of a split face unit?
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    This is a great question HJ – one that causes a lot of confusion and many (often conflicting) opinions. No, this assembly would not need a vapor retarder. In fact, I’m not a big fan of vapor retarders in single wythe masonry construction in general as they tend to cause two real problems for every pseudo-concern they intend to solve. (There are some exceptions – such as indoor pools in northern climates – which shouldn’t automatically trigger the inclusion of a vapor retarder, but rather an assessment of the vapor permeance of the wall assembly being used.) Dew point is another common point of confusion. For most of the U.S. where we heat during the winter (and the vapor drive is generally to the exterior) and cool during the summer (reversing the vapor drive to the interior), the vapor retarder will be on the wrong side of the wall for some portion of the year. (And the last thing any assembly deserves is a vapor retarder on both sides of the wall as the wall would never be allowed to dry.) Far more moisture can get into (or through) a wall assembly by air leakage rather than vapor diffusion. Hence, starting with a solid grouted assembly a great start – but good performance also relies on good design and construction practices. The units and mortar should contain an integral water repellent; openings (and if present) copings should be flashed; mortar joints tooled to a concave profile; and if appropriate, consider a post-applied sealant. More detailed discussion is provided in NCMA TEK 19-2B. TEK 19-02B.pdf
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    COMcheck is a powerful tool for energy code compliance, but the correct input of thermal properties is important. While COMcheck has a few pre-developed concrete masonry wall sections that can be used, it is usually more accurate to input the information yourself using the 'Other Wall' option. To do this when creating a wall, choose the "Other (U-Factor Option)" and then select "Other Mass Wall". Once you do that, you will have to input the wall U-Factor and Heat Capacity. Both can be determined using NCMA resources (all available on the NCMA Solutions Center): For U-Factor, you can use TEK Note 6-1C, TEK Note 6-2C, the R-value/U-factor Calculation Spreadsheet, or the Thermal Catalog of Concrete Masonry Wall Assemblies. For heat capacity, you can use NCMA TEK Note 6-16A.
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    This white substance is known as efflorescence. Efflorescence is caused by a combination of the following three circumstances: 1) A soluble compound exists in the masonry unit; 2) Moisture is present within the masonry capable of dissolving these soluble salts; and 3) As the masonry dries, the dissolved solids are carried to the surface where the moisture evaporates leaving the efflorescence on the surface of the unit. If any one of these circumstances is prevented, then efflorescence will not occur. To learn more about efflorescence, how to account for it in design and construction, and how to remove it from a masonry wall, refer to TEK Note 8-3A (see attached). TEK 08-03A (1).PDF
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    There are two general types of water repellents for CMUs: 1) Surface Treatments; and 2) Integral Water Repellents. Surface treatment repellents are applied to the weather-exposed side of the wall after the wall is constructed. In addition to water repellency, surface treatment repellents can also improve the stain resistance of the wall. Integral water repellents are admixtures added to the CMU and mortar materials before the wall is constructed. The water repellent admixture is incorporated into the concrete mix at the block plant. This way, each block has water repellent throughout the concrete in the unit. For mortar, the water repellent is added to the mortar mix. It is critical when using integral water repellents that the repellent is incorporated into both the block and the mortar to ensure proper performance of the wall. For more information on the two types of the repellents, refer to TEK Note 19-1A (see attached). TEK 19-01 (2).pdf
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    A CMU is broken down into three parts, as depicted below: 1) Face shell – Material that creates the front and back of the unit 2) Webs – Material that connects the face shells together 3) Cells – Open areas between the webs that allow for the placement of reinforcement, grout or insulation
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    In most situations, two layers of WRB complying with ASTM D226, E2556, or approved equal are required for MSV installation. However, there are some instances where this requirement can differ: - - Building codes may allow a single layer of a WRB to be used when a drainage space (rainscreen) is incorporated behind the stone assembly. Requirements for the rainscreens vary by region. Verify with the local jurisdictional requirements regarding the use an application of rainscreens. - - In the event a cladding transition occurs, the number of layers of WRB necessary behind the non-manufactured stone veneer cladding is dependent upon the material selected (i.e. zero layers, 1 layer, 2 layers, etc.). However, once the transition occurs to AMSV then two (2) layers of WRB must be present. - In the presence of concrete/masonry backup assemblies, WRBS are not required. For details and more information on WRB, please refer to the MVMA MSV Installation Guide (click here).
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    The most direct and efficient way (aside from testing the assembly) to determine the fire rating of an existing assembly is to use the calculation method. This is described in detail in TEK Note 7-1C (see attached). TEK 07-01C3.pdf
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    How can I determine the fire resistance of an existing assembly?
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    When a concrete masonry assembly is provided with an exterior wall covering (such as an anchored or adhered veneer, stucco, etc.), then the requirements of Section 1405 of the 2015 International Building Code would apply as noted. As stipulated in Section 1403.2 of the IBC however: "A weather-resistant exterior wall envelope shall not be required over concrete or masonry walls designed in accordance with Chapters 19 and 21, respectively." If any of the materials listed in Table 1405.2 are installed over a concrete masonry assembly in accordance with the provisions of Section 1405, then they are essentially deemed-to-comply as an 'exterior wall covering'. But as stated in Section 1403.2, these coverings are optional for concrete masonry systems. Certainly exterior concrete masonry assemblies are still required to provide weather protection, but there are many other ways to accomplish this without the use of wall coverings. As discussed in TEK 19-2B (attached in previous post), a single wythe concrete masonry assembly can be detailed as a drainage system (including the use of flashing), or as a barrier system (with would not employ the use of flashing).
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    Though Masonry construction is exempted from the requirements of providing an Exterior Wall Envelope, aren't we still required to provide Weather Protection for exterior walls such as in 2015 IBC "COVERINGS; 1405.2 Weather protection. Exterior walls shall provide weather protection for the building. The materials of the minimum nominal thickness specified in Table 1405.2 shall be acceptable as approved weather coverings...." ?
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    The industry recommendations for reinforced fill are: - For walls less than or equal to 10 feet (3 m) in height tall, a soil that has less than 35% fines (fraction finer than #200 sieve), a plasticity index (PI) of less than 20, and a liquid limit (LL) less than 40 is recommended. - For walls taller than 10 feet (3 m) and less or equal than 20 feet (6 m), a soil that has less than 35% fines (fraction finer than #200 sieve), and a plasticity index (PI) of less than 6 is recommended. - For walls taller than 20 feet (6 m), a soil that has less than 15% fines (fraction finer than #200 sieve) with a plasticity index (PI) of less than 6 is recommended.
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    While industry recommendations encourage the use of flashing and other water control technologies in concrete masonry construction, it is not required by code. Cladding systems, however, such as masonry veneers, are required by code to be flashed to direct any moisture that penetrates the cladding to the exterior of the building. Because flashing is not code-required, it is often a victim of value engineering. While the strength of concrete masonry isn’t negatively impacted by the presence of moisture, if water is trapped inside of a concrete masonry assembly it can lead to aesthetic and serviceability issues. Efflorescence is the most common byproduct of poor moisture control strategies in concrete masonry construction, but others include corrosion of metal accessories and rust streaks on the surface of the wall, and moisture leaking into the interior of a structure. A number of industry recommendations for the control of moisture in single wythe concrete masonry construction is included in TEK 19-2B (attached). Many other related resources are available on NCMA's Solutions Center (www.ncma-br.org). TEK 19-02B.pdf
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    Fundamentally there is very little difference as each block is produced using the same three basic constituent materials: cement, water, and aggregate. The term ‘cinder block’ was coined in the early 20th century when producers of concrete masonry units began to use cinder aggregates during the manufacturing process. These cinder aggregates could be naturally occurring (such as pumice and scoria), manufactured (such as expanded shale or clay), or a by-product of another process (such as bottom ash from coal combustion). Eventually the name stuck and the terms cinder block and concrete block became interchangeable references to concrete masonry units. A more detailed discussion on this topic can be found in the attached document. FAQ 20-14 - Concrete Block vs Cinder Block.pdf