SPECIFYING PRE-BLENDED MORTAR FOR ADHERED VENEERS

When specifying interior or exterior veneer systems that are adhered with mortar, it is advisable to review the industry standards and model specifications that can be customized for specific projects, whether new construction or renovation. In a standard, three-part specification format following the CSI or MasterFormat system, it is found in Division 4, Masonry, usually under Section 04 05 00 or a subsection of that. Some of the relevant items to address are highlighted as follows.

Part 1 - General

The scope of the specified work for the adhered veneer mortar(s) and related work as well as any definitions should be called out. It is advisable to call for a pre-installation meeting and to request submittals based on the project needs, including the request for LEED documentation if any relevant credits are being pursued. Quality assurance can be addressed by calling out the relevant ASTM and other standards that need to be met as described previously. Project conditions and product storage should all be addressed in typical fashion. If large quantities of pre-blended mortar are anticipated, then delivery and protected storage will be important.

Part 2 - Products

All of the different performance and material criteria for the mortar(s) being specified need to be called out. This includes whether the mortar shall be pre-blended or site-mixed. The specific material listings following the ASTM and ANSI standards should be identified including any allowable admixtures. If pre-blended mortar is specified as the only acceptable product, then the type of mortar (standard, polymer-modified, or thin-set) needs to be called out. Further, any scratch coat, bond coat, or grout formulations should be identified including a reference to the types of locations where each is intended to be used (interior, exterior, special project conditions, etc.). Any related materials or accessories needed such as lath, flashing, screeds, etc. should either be specified in this spec section or be referenced in other relevant specification sections.

The details of each mix of mortar used in the project will need to be clearly identified in the specifications and coordinated with locations as shown on the drawings. If colors are selected for exposed mortars or grouts, then they need to be selected from manufacturers or industry data.

Part 3 - Execution

As with any site-installed product, the installation requires multiple steps which need to be clearly articulated in the specification in order to achieve the best results.

• Examination and Preparation: The importance of this step should always be stressed. In addition to the architect, the installer and general contractor or construction manager should review and examine the substrate for conditions that may affect the installation or the overall performance. This can include a determination that the wall does not vary more than ¼ inch from a true plan in a 10-foot span. It may also require the use of independent testing agencies to verify moisture content in a concrete or masonry structural wall. Any issues will need to be corrected, likely by the general contractor, if they are found to be out of compliance with the stated requirements.
• Installation: The recommendations and procedures outlined in this course based on the industry standards and manufacturer’s recommendations should always be the basis for a proper installation of adhered veneer products.
• Protection: Once installed and finished, the surface should likely be able to withstand use by remaining construction personnel on the project. However, the general contractor should be instructed to cover and protect the surface as appropriate to the jobsite conditions, particularly if the mortar and grout require any extended time to set and cure.
• Cleaning: Cleaning of any excess mortar should be done as part of the installation. Final cleaning and finishing should be based on the recommendations of the veneer manufacturer. Generally, harsh chemicals should be avoided for cleaning, such as acid, as should abrasive tools such as wire brushes or power washers.

Photo courtesy of SPEC MIX and National Concrete Masonry Association (NCMA)

The proper installation of adhered veneers includes proper attention to the substrate such as a wood-framed wall, a concrete masonry unit (CMU) wall, or any other type of wall.

Photo courtesy of SPEC MIX

Proper specification of mortar materials consistent with the type of veneer products being installed helps to create the best design and construction results.

When specified and installed correctly, an adhered veneer system held in place with the correct mortar can readily provide the desired look and the long-term performance characteristics that are intended.

CONCLUSION

Adhered veneer systems have been shown to provide architects, interior designers, construction professionals, and building owners/managers with an appealing, long-lasting solution for interior and exterior walls and surfaces. They offer exceptional design versatility with a great range of thin but durable products available. The selection of the correct mortars and attention to detail regarding the design, specification, and installation of the system are key to a successful project.

Peter J. Arsenault, FAIA, NCARB, LEED AP is a nationally known architect and a prolific author advancing more sustainable buildings through the power of design. www.pjaarch.com, www.linkedin.com/in/pjaarch