1. ICC ES AC51 Draft Changes, Masonry Veneer Manufacturers Association (MVMA) Comments, dated September 24, 2007, compiled by John Woestman.

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1 #15 ICC EVALUATION SERVICE, INC. Evaluate P Inform P Protect To: From: ICC-ES Evaluation Committee Elyse Levy, S.E. Date: October 5, 2007 Subject: Proposed Revisions to the Acceptance Criteria for Precast Stone Veneer, Subject AC R1 (EL/RK) MEMO In response to the proposed revisions to the Acceptance Criteria for Precast Stone Veneer, Subject AC R1, two documents containing public comments were received as follows: 1. ICC ES AC51 Draft Changes, Masonry Veneer Manufacturers Association (MVMA) Comments, dated September 24, 2007, compiled by John Woestman. 2. A letter from William F. Egan of BASF, dated September 12, Based on staff review of these comments, the items listed below are submitted for committee consideration. (Please note: Proposed revisions to the published criteria are shown in strikeout/ underline format. Italicized text has been added subsequent to the posting of the proposed criteria.) 1. Section 1.2 Scope is proposed to read as follows: This criteria applies to precast stone veneer adhered with mortar to the exterior face of exterior walls and, at the report holder s option, to interior wall surfaces. The veneer system is considered a variation of exterior plaster regulated by IBC Section 2512, IRC Section R703.6, BNBC Section , SBC Section and UBC Section 2508, and a variation of adhered masonry veneer regulated by IBC Section , BNBC Section , SBC Section and UBC Sections and The veneer may be adhered to backings consisting of concrete, masonry, or cement plaster or masonry mortar applied over metal or wire fabric lath. Reason for revision to the original proposal: Clarification in response to suggestion from the MVMA. 2. Section 1.3 Codes and Referenced Standards and Table 1 are proposed to be revised to include the following: ASTM C 331, Specification for Lightweight Aggregates for Concrete Masonry Units. ASTM C 926, Specification for Application of Portland Cement Based-plaster. Chicago Regional Office P 4051 West Flossmoor Road, Country Club Hills, Illinois P (708)

2 AC R1 2 The editions of these standard are proposed to be: IBC IRC BNBC SBC UBC C C a -98a -98a -94 N/A Reason for revision to the original proposal: Coordination with text of criteria. 3. Section Backing is proposed to read as follows: The surface to which the veneer units are adhered. The backing may be concrete, masonry or a scratch coat of cement plaster or masonry mortar applied over metal or wire fabric lath. Reason for revision to the original proposal: The typical installation described in current evaluation reports uses masonry mortar (Type S, N and / or M) applied over the lath in lieu of the cement plaster prescribed by the codes for exterior plaster. 4. Section Precast Stone Veneer is proposed to read as follows: An adhered veneer made from lightweight precast concrete, comprised of portland cement, water and mineral aggregates, with or without other materials. Units of precast stone veneer are formed and cast offsite to provide the appearance of stone or other masonry materials. Reason for revision to the original proposal: As pointed out by the MVMA and seen in evaluation report submittals, products evaluated under this criteria can resemble other masonry materials, such as brick. 5. Section Scratch Coat is proposed to read as follows: A backing of cement plaster or masonry mortar applied over metal or wire fabric lath, to which the veneer units are adhered. Reason for revision to the original proposal: Clarification. Also, see Item 3, above. 6. Section Veneer System is proposed to read as follows: The combination of the veneer units with the supporting materials used to affix the veneer units to the supporting wall, including joint mortar, setting bed, and scratch coat, as applicable. Reason for revision to the original proposal: Clarification in response to an MVMA comment. 7. Section Aggregate is proposed to read as follows:

3 AC R1 3 Type and size designation must comply with ASTM C33, or ASTM C 330 or ASTM C 331, except gradation requirements need not apply. Gradation, however, shall be specified. Reason for revision to the original proposal: Response to a comment in the MVMA letter. Currently, at least one applicant uses aggregate conforming to ASTM C Section Admixtures is proposed to read as follows: Description and purpose of the admixture shall be specified. Purposes may include, but not be limited to, expediting setting, enhancing durability and additional improving workability. Reason for revision to the original proposal: Clarification in response to an MVMA comment. 9. Section Mortar is proposed to read as follows: Describe the type of mortar used for the setting bed and/or scratch coat. Mortar must comply with IBC Section , IRC Section R607.1, BNBC Section , SBC Section or UBC Section , as applicable. Describe the thickness of the setting bed. The setting bed thickness shall be a minimum of 3 / 8 inch (9.5 mm) thick and a maximum of 1 1 / 4 inches (32 mm) thick. Reason for revision to the original proposal: Clarification. As noted above, masonry mortar is commonly used for the scratch coat, as well as for the setting bed. 10. Section Cement Plaster is proposed to read as follows: If applicable, ddescribe the type of plaster used for the scratch coat, in accordance with ASTM C 926. Reason for revision to the original proposal: Clarification. Cement plaster is not always used in the scratch coat. 11. Section Lath is proposed to read as follows: Describe the type and weight of the lath; the type, size and spacing of the fasteners used to attach the lath to the backing supporting structure. The lath and its installation shall comply with IBC Section 2510, IRC Section R703.6, BNBC Section 2506, SBC Sections 2503 and , or UBC Section 2506, as applicable. Reason for revision to the original proposal: Clarification in response to an MVMA comment.

4 AC R Section is proposed to read as follows: Preparation of test specimens, including complete description of the specimen components, density, mix proportions and curing. Reason for revision to the original proposal: Suggested by MVMA, because density is determined through testing (See Section of the proposed criteria) and is not a description. 13. Section is proposed to read as follows: Statement as to whether the systems are acceptable test results meet the conditions of acceptance given in the criteria. Reason for revision to the original proposal: Clarification requested by the MVMA. 14. Sections , , and are proposed to read as follows: Compressive strength tests of veneer units mixture must be conducted in accordance with ASTM C 192 and ASTM C 39 Section 4.3. Minimum requirements are 1800 psi (12.4 MPa) average for five specimens, and 1,500 psi (10.3 MPa) for individual specimens. See Section 4.3. The results for any one sample cannot vary by more than 10 percent from the average for all samples Tensile strength tests of veneer units mixture must be conducted in accordance with ASTM C 190. See Section 4.5. The results for any one sample cannot vary by more than 10 percent from the average for all samples Flexural tests of veneer units mixture must be conducted in accordance with ASTM C 348. See Section 4.4. The results for any one sample cannot vary by more than 10 percent from the average for all samples. Reason for revision to the original proposal: Clarification. These tests are performed on specimens prepared specifically for the tests, not on veneer units representative of typical production. 15. Section is proposed to read as follows: Samples shall be taken from pieces of broken veneer units broken during the compressive, flexural and tensile strength tests. Reason for revision to the original proposal: In response to a question raised in the MVMA letter, regarding Section The requirement that the specimens used for the water absorption test be taken from pieces of veneer broken during the compressive, flexural and tensile strength tests was questioned. Staff supports the continued use of

5 AC R1 5 broken pieces of veneer, as this requirement has been included in AC51 since the criteria was first issued in June The required use of broken pieces of veneer taken from the strength tests was originally based on 1988 UBC Standard for roof tile (which later became 1997 UBC Standard 15-5). When the precast stone veneer is initially supplied, it may have a coating, paint or other finish that may deteriorate over time. By using broken pieces of veneer in the absorption testing, we are able to evaluate the absorption rate of the veneer without any coating. However, staff does concur with the commenter that the pieces should be taken from samples of the veneer units, which are representative of actual production, and not from cylinders or other specially prepared specimens used in the strength tests. Staff believes the wording proposed above to be consistent with the original intent of AC51. In acknowledgment of other issues that were raised in the letters that were received, staff offers the following comments: C1. While this memo proposes the expansion of the definition of precast stone veneer, given in Section of the proposed criteria, staff does not support deletion of the term stone throughout the acceptance criteria, as requested by the MVMA, for the following reasons. a. No proposal for an alternate term was given. b. IBC Table gives a minimum thickness for precast stone facing which is the basis for the minimum thickness required by AC51. c. The requirements of AC51 are not applicable to other adhered masonry veneer products, such as clay brick. d. Other acceptance criteria reference this criteria. Changing the name and terminology will make coordination difficult. C2. Staff does not support changing the term pattern to texture, as requested by MVMA. We are interested in the repetitive grouping of veneer units, not the smoothness or roughness (texture), so pattern is a more accurate term. C3. Both the MVMA and BASF would like to see the criteria address lath materials other than metal or wire fabric lath. Many factors must be considered when determining if alternate lath materials are equivalent to those prescribed in the code. At the moment, ICC-ES does not have a report application for precast stone veneer using an alternate lath material. Therefore, the proposed criteria has not been revised to include provisions for alternate lath products. ICC-ES welcomes the opportunity to revise AC51 at a later date, upon receipt of a report application for a precast stone veneer system using an alternate lath material, and welcomes input from industry as to how these alternate materials should be evaluated.

6 AC R1 6 C4. The MVMA would like the criteria to address veneer units manufactured using cements other than those conforming to ASTM C 150. At the moment, ICC-ES does not have a report application for precast stone veneer using cement which does not conform to ASTM C 150. Therefore, alternate cement use has not been researched and the proposed criteria has not been revised in this regard. ICC-ES welcomes the opportunity to revise AC51 at a later date, upon receipt of a report application for a precast stone veneer system manufactured using an alternate cement material. C5. The MVMA has expressed concern, regarding Section of the proposed criteria, that by requiring compliance with IBC Section , a scratch coat and a brown coat will be required, instead of a single scratch coat. However, the second sentence of IBC Section reads, If the plaster surface is to be completely covered by veneer or other facing material,... plaster application need be only two coats, provided the total thickness is as set forth in ASTM C 926. Since the plaster in this case is covered by the precast stone veneer, only two coats of plaster are required. The scratch coat is the first coat and the setting bed is the second coat. The intent of the criteria is that the setting bed be in compliance with the code requirements for the brown coat of exterior plaster. C6. A question was raised in the MVMA letter, regarding Section of the proposed criteria, as follows: If the veneer units must weigh less than 15 pounds per square foot, why not report the thickest profile and combine that with the density results of the heaviest concrete mix design? In contrast, multiple evaluation report applicants have requested that we consider the average weight of the veneer units in a pattern, because they produce veneer units that are not of uniform thickness and/or produce individual pieces of veneer weighing more than 15 psf, that are used in patterns where the average weight of the pattern is within the 15 psf limit. C7. A question was raised in the MVMA letter, regarding the requirements of Section of the proposed criteria as follows: Does this mean the thinnest part of a veneer unit or the thinnest profile based on the average thickness of each unit in that profile? What if I have a veneer unit with a uniform thickness of 1 inch compared to a veneer unit with average thickness greater than 1 inch containing peaks and valleys where some sections of the unit would be less than 1 inch? In response, due to the great variety of veneer unit products and the number of producers, there is not a hard-and-fast rule that can be added to the criteria. The resolution of this question should be left to the applicant and the testing laboratory. Due consideration should be given to testing the veneer units that are most susceptible to deleterious effects from freezing and thawing. If the applicant would like input from ICC-ES prior to testing, a testing plan can be submitted for review. C8. The requirement of Section 4.5 of the criteria for tests in accordance with ASTM C 190 has not been removed from the criteria, as suggested by the MVMA. While this standard has been withdrawn by ASTM International, no comparable test has replaced it. Also, this standard is available through Global Engineering Documents.

7 AC R1 7 C9. A comment was made by the MVMA regarding Section of the proposed criteria as follows: The variation of the compressive strength of the mortar is outside a stone manufacturer s control. The manufacturer of the adhered masonry veneer shouldn t be held to the variability of compressive strength of mortar (i.e. the 10% limit). We agree that the veneer manufacturer does not control the strength of the mortar used in the field. This is why it is necessary for the shear bond testing to be performed using mortar which is at or near the minimum allowed for code complying mortar of that type. C10. The MVMA commented that the weep screed should be optional. However, IBC Section requires weep screeds for exterior plaster. The size and spacing of the holes required in the weep screed are based on Section of ACI Without the use of weep screeds, it is not clear that an adequate means of drainage is provided, as required by IBC Section ICC-ES welcomes the opportunity to revise AC51 at a later date to incorporate an alternate approach to meeting the intent of the code, if so desired by a report applicant. C11. Staff would appreciate committee and industry input regarding further revisions to Section of the criteria, which may be proposed at a later hearing. We are trying to determine if ASTM C 482 is the most appropriate test method for determining shear bond between the setting bed and concrete or masonry substrates. Issues we are considering include: EL/RK/ll 1. Testing in accordance with ASTM C 482 is done on specimens which are bonded to a molded substrate which is 6 inches by 4 1 / 2 inches by 2 inches (152 by 114 by 51 mm) in depth. Therefore, it may not be practical to use this test method in conjunction with specimens having substrates of concrete or masonry. 2. Since the product being evaluated is the veneer units, we want to evaluate the bond performance of the veneer units to the setting bed, and the adequacy of the specified setting bed. How well the mortar setting bed bonds to various substrates, such as concrete and masonry, depends partly on the quality of the surface preparation of the backing, and the quality of the installation. Report applicants have indicated that these factors might be considered to be outside the control of the veneer manufacturer. Therefore, their position is that bond strength testing using the specified cement plaster or masonry mortar scratch coat material, and not concrete or masonry, may be considered adequate. However, the efficacy of the system is also dependent on the bond of the setting bed to the backing. 3. Staff has been told, by one testing professional, that the failures of precast stone that he has investigated have been due to poor quality of the back surface of the veneer unit or improper installation, not failure of the bond between the setting bed and the backing. Further information on the common problems found with precast stone veneer would be useful.