Lightweight Natural Stone Cladding – a Great Option for Select Buildings

WorldMed, Lousiville, KY

Architectural designers have myriad choices when selecting and specifying cladding systems for high end commercial and institutional buildings. Lightweight natural stone cladding (LNSC) can be a great option for select commercial, institutional, and transportation projects but are not as well-known as other high-end solutions. As with many other scopes, there are many factors that impact and ultimately determine the cladding design and specification, including: budget, building height, structural support, climate zone, performance, sustainability, code compliance, aesthetics, lead time, etc.

Institutional buildings often have less stringent budgeting constraints than other types of building projects. At the same time, museum, university, hospital, religious, and other institutional projects are usually designed with longer life spans than other project types. As mentioned above, many factors affect the decision-making process. Below is a quick overview of several of these factors. As this article relates to lightweight natural stone cladding systems, we refer to specific information related to TerraCORE Panels, a Dallas-based leading provider that we represent.

 

Budget: As with many other parameters, cost of materials and labor to furnish and install cladding systems can vary significantly from region to region. For this discussion we reference common or typical cost to a general contractor in major Texas cities. For projects with cladding budgets (furnish & install) in the $30’s to $50’s per sf, a limited selection of lower cost materials such as EIFS, Stucco, Single skin metal panels, Tilt-Up, and Poured-in-place concrete may fit the bill. Higher end projects with cladding budgets in the $60’s or $70’s per sf will have more options including masonry, porcelain, natural stone, and MCM (metal composite materials). Lightweight natural stone cladding systems with natural stone on aluminum honeycomb will generally fall in the latter category.

 

Building height & structural support: Single story and other low-rise buildings can be economically clad with either lightweight or heavy cladding systems, as heavy stone or masonry walls can be simply stacked, transferring their dead load to foundations & concrete slab. On the other hand, multi-story buildings must include a more robust perimeter framing design if heavy cladding systems are being considered. Lightweight natural stone cladding systems typically weigh around 6 lbs./sf. And having a high flexural resistance, installation for many low to mid-rise projects will only require 16-gauge metal studs at 16” on-center. This may translate to important savings in structural framing costs when compared with masonry or dimension stone walls, which can weigh 40+ lbs/sf.

 

Climate zone & performance: Different regions around the country have different climates and consequently, different thermal insulation requirements. Additionally, many cities, counties and states have adopted green and/or sustainable building codes, some of which include continuous insulation requirements.

 

Chapel, St. Joseph Hospital, Denver, CO

While Lightweight natural stone cladding systems don’t have an intrinsic thermal insulation value, they can be designed in conjunction with a wide array of insulation systems, including commercially available continuous insulation solutions that meet the most stringent thermal efficiency code requirements.

 

Sustainability: Many institutional buildings are designed to meet LEED certification or other sustainable design & construction programs. This is a complex subject that cannot be addressed succinctly and often involves specialized consultants for any given project. There are many thermal efficiency and sustainability parameters, so here we focus exclusively on select LEED points: Lightweight natural stone cladding systems can contribute points for the following credits: Materials and Resources Credit Building Product Disclosure and Optimization – Sourcing of Raw Materials (recycled content criteria of this credit); Materials and Resources Credit Building Product Disclosure and Optimization – Material Ingredients (Health Product Declaration criteria of this credit).

 

Code compliance (flame spread): Code compliance to meet the NFPA 285 standard is required for certain projects, and may also be desirable on projects without such a requirement. Intertek conducted testing for TerraCORE Panels on a Caliza Capri Stone + Aluminum Honeycomb Panel to evaluate flame spread. Testing was conducted following NFPA 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load Bearing Wall Assemblies Containing Combustible Components, 2012. Based on the data from the December 2016 test, the assembly met the conditions for acceptance of the above-mentioned standard. It must be noted that other TerraCORE Panel configurations may require their own testing following the NFPA 285 standard method.

 

Faux column made with TerraCORE Panels

Aesthetics: Owners, developers, and designers have many options in terms of façade or building envelope material, color, texture, and aesthetics in general. Even when a stone appearance is desired, there are several distinct options including adhered stone (cultured or natural), split-face CMU, dimension stone, and panelized natural stone. Lightweight natural stone panels are available with virtually any stone selection including granite, marble, travertine, limestone, sandstone, onyx, and most other quarried large format stones, in panels up to 4’ x 8’. Select stones may have different finishes including rough or fine water jet, honed, polished, and other custom finishes. Lightweight natural panels are custom fabricated according to approved shop drawings and may include returns of up to 8”, giving the impression of massive stones.

 

Lead time: Each project is unique and has its own limitations, constraints, and requirements based on the selected project delivery method, critical path schedule, budget, and other factors that determine maximum lead times for certain major materials, products, and systems. For complex, highly engineered systems such as lightweight natural stone cladding, a substantial lead time in the order of 16 to 20 weeks (or longer) may be required to accommodate stone selection and sourcing, design assist, shop drawings production and approval, manufacture, shipping, and delivery. For projects with short lead time requirements for their cladding systems, Lightweight natural stone cladding systems may not be a suitable option.

 

Lightweight Natural Stone Cladding – a Great Option for Select Buildings Summary: We fully share the opinion that no cladding system is right for every project. Building design and construction is a highly complex and specialized field, and many variables impact the decision-making process to select the right cladding system for any given project. Lightweight natural stone cladding systems, as offered by TerraCORE Panels, can be an excellent choice for projects that share some or all of the following characteristics. More in-depth information can be found at https://apcs-sales.com/products/terracore/ and at http://www.terracorepanels.com/
• Budget (furnish & install) in the $60’s/sf or higher
• Single story to Multi-story design to achieve savings in structural framing
• Any thermal insulation requirements including continuous insulation
• LEED Certification, up to two points
• NFPA 285 standard flame spread approval
• Natural stone in panels up to 4’ x 8’ with or without returns
• Unlimited stone types, colors, textures, and finishes
• Lead time of at least 16 to 20 weeks