Read More Articles Adhered Manufactured Stone Veneer: Installation, Investigation and Repair December 7, 2020 Share What is Adhered Manufactured Stone Veneer (AMSV)Adhered manufactured stone veneer, commonly referred to as AMSV, is a lightweight, non-load bearing masonry cladding that simulates the appearance of natural stone. It is applied very much like stucco in that it is installed on masonry and frame wall assemblies, and can be installed over different types of rigid sheathing, including gypsum, plywood, and oriented strand board (OSB). Like stucco, when installed on framing, it requires two (2) layers of water-resistant barrier (WRB), metal lath secured to the framing with corrosion-resistant fasteners, and a scratch coat. Unlike stucco, the outermost or finish surface consists of the manufactured stone pieces adhered to the scratch coat with a mortar setting bed.
Although adhered manufactured stone masonry veneer (MSV) has been in use for over 40 years, ASTM standards governing the units and their installation are brand new, having just been first published within the last five years. Before that, there was building code acceptance criteria, but not all manufacturers complied with it, leading to variability in constituent materials, product characteristics, and field performance. According to Chris Hines, Technical Leader at Boral Stone Products LLC, Leaders in the industry started thinking that there should be a governing standard,to agree on standardized materials, testing and performance. After more than eight years of work through ASTM International, Standards C1670, Specification for Adhered Manufactured Stone Masonry Veneer Units, and C1780, Installation Methods for Adhered Manufactured Stone Masonry Veneer Units, were born.
When Hines started in this industry, he said therewas little to no language in the codes specifically addressing MSV. The International Building Code (IBC) and International Residential Code (IRC) included some general language on adhered masonry veneer, a category which includes MSV as well as adhered concrete masonry and adhered clay masonry units. However, even those codes essentially referred to the masonry model building code, Building Code Requirements for Masonry Standards (TMS 402), which also addressed only the broader category of adhered veneers.
Even though MSV is a veneer and does not carry structural load, ASTM C1670 includes a requirement that MSV units meet a minimum compressive strength as an indicator of product durability and consistency. Other concrete masonry units are manufactured and cured before being tested in compression. However, due to the inherent difficulty in producing consistent results from units of such varied sizes and shapes, the concrete used to manufacture the MSV units is tested as a cylinder rather than testing the units themselves. Each concrete mix is poured into cylinders using ASTM C31, Standard Practice for Making and Curing Concrete Test Specimens in the Field and tested in compression using the procedures in ASTM C39, Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. (See Figure 1).
MSV units are required to have a minimum thickness of 1/4 inch, although there may be thinner spots in the area within 1/2 inch of the unit edge. The average unit thickness must be no reater t an 2-5/8 inches, and units cannot exceed 36 inches in any face dimension, nor more than 5 sqft2 in total face area. Finally, the weight of the units cannot exceed 15 lb/sqft2. These requirements for size and weight are consistent with current building code requirements for adhered veneer masonry units.
Even though it is a popular cladding material, adhered manufactured stone masonry veneer has historically not had a national, consensus-based specification to set minimum properties for these products, which in turn has sometimes been a source of performance issues in the field.
Adhered manufactured stone masonry veneer (AMSMV or MSV) is a manufactured concrete product increasingly used to economically provide the look of natural stone to buildings large and small. MSV is known by a variety of names throughout the country, including precast stone veneer, architectural precast veneer, cast stone veneer, simulated stone, as well as a by several of the popular brand names under which it is sold.
ZEMENT STONE manufactured stone veneer, including Color Palette ze Earth Collection and Legacy Stone product lines, are used as adhered, non-load bearing exterior or interior veneers on non-fireresistance-rated wood framed or light-gage steel stud construction, concrete or concrete masonryblock walls.
When the masonry stone veneer (MSV) was first introduced into the market, manufacturer recommendations were the only available guidelines to install the product as there were no industry-wide practices or standards.
Of course, leaving a 4\" gap at the ground isn't the prettiest looking thing in the world, but there is a solution; simply have the weep screed terminated at least 4\" above the ground, and have another layer of masonry veneer installed below it, as shown in the diagram below.
When masonry veneer has a vertical transition to something like wood trim, windows, or other siding materials, it should have a 3/8\" gap left between the two different materials. This gap needs to have a foam backer rod pushed behind it, and then filled with sealant to help prevent water intrusion. This is rarely done.
Masonry veneer needs to be kept 2\" above roof surfaces to help prevent water from wicking up in to the wall. The photo below shows a common deviation, where the masonry veneer actually touches the shingles. This is just asking for trouble.
Of course, this is only a partial list of the things that can go wrong on a stone veneer installation. If you're planning to have this material installed on your home, make sure the installation instructions are followed to help lower the potential for water intrusion. If you're buying a home with masonry veneer already installed, treat it the same way you would newer stucco and have intrusive moisture testing performed. The process is the same as for stucco.
Specific problems noted with the visible components include, but may not be limited to: (list all that apply) Weep screeds are missing at the base of the wood frame walls. Weep screeds are missing at the tops of window and door openings. There is no caulk between other materials and the masonry veneer at windows, doors, and adjacent trim. The masonry veneer is in contact with the ground. The masonry veneer is in contact with paved surfaces. The masonry veneer is in contact with roofing materials. Kick-out flashings are missing where roof eaves meet the masonry veneer. Metal lath is visible between stones, indicating that the proper base coats of mortar were not applied prior to installation of the stone.
The lack of proper detailing and flashing may result in water penetration behind the siding, resulting in structural damage. The installation of the manufactured stone veneer should be evaluated, compared to the specific installation requirements of the stone manufacturer and the MVMA, and repaired or replaced as deemed necessary by a licensed general contractor or masonry contractor experienced with installation requirements for manufactured stone veneer.
NCMA is an association of producers of concrete masonry products, and suppliers of products and services related to the industry. NCMA offers a variety of technical services and design aids through publications, computer programs, slide presentations and technical training.
There are some notable issues with the way the claddings were installed compared to the details of installation these manufacturers specify. This is noted on the siding with regard to clearances and kick-outs where the roofline meets a sided wall and a gutter terminates into a sided wall plane as well as some of the stone installation details. At the time of my visit when we were talking to the representative from Centurion He made some comments about the flashing around the windows as being the responsibility of others. While this is true in the installation of the window and its associated SAF (self adhering flashing) ((the window tape)) it should be noted the masonry contractor is responsible to not cover up a poorly detailed assembly and communicate these deficiencies to the general contractor.
Adhered thin stone and brick veneers have gained popularity in the past 15 years because of their ability to replicate the look and feel of full-bed masonry with increased installation speed, a reduction in wall thickness, and without the additional weight of traditional full-bed masonry. Indeed, it is often difficult for the casual eye to differentiate between full-bed and adhered, or manufactured and natural stone veneers (Figure 1).
Full height walls less than 3 m above gradeWith full-height walls that do not exceed 3 m (10 ft) above grade, it is typically prudent to provide drainage behind the adhered masonry veneer, even when local building codes do not require it. Full-height walls usually have openings for doors and windows, as well as penetrations in the envelope for services that can be potential sources of water ingress behind the cladding.
Drainage can be provided in many ways. The most popular is a drainage mat or vinyl/treated wood strapping. If drainage mats are used, it is important the product is sufficiently incompressible to prevent excessive deflection of the lath and scratch coat. Excessive deflection can cause joint cracking and de-bonding of the adhered units.2 Figure 4 provides an isometric with a drainage mat behind the lath used for anchoring the masonry veneer.
Full-height walls exceeding 3 m above gradeWith full-height walls that exceed more than 3 m (10 ft) above grade, it is prudent to have the veneer system designed and stamped by an engineer certified to practise in the local area. As with walls less than 3 m above grade, it is a good idea to provide for drainage behind the adhered masonry veneer. 59ce067264