Honeycomb-Backed Stone Cladding Systems - A Great Choice for Commercial and Institutional Buildings

By Victor J Yakin

Architectural designers have many choices when selecting and specifying cladding systems for high-end commercial and institutional buildings. As with many other scopes, there are many factors that influence and ultimately determine the cladding design and specification, including, among others: budget, building height, structural support, climate zone, performance, sustainability, code compliance, aesthetics, lead time, etc.

Institutional buildings often have less rigorous 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 outline of several of these factors.

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 article we reference anecdotal information on such costs to a general contractor in Texas cities. For projects with cladding budgets (furnish & install) in the $30's to $50 per sf, a limited selection of lower cost products such as EIFS, stucco, single skin metal, Tilt-Up, and poured-in-place concrete may fit the bill. Higher end projects with cladding budgets in the $50's to $70's per sf will have more options including masonry, porcelain, lightweight stone panels, dimension stone, precast architectural concrete panels, phenolic panels, and ACM (aluminum composite material).

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

Climate zone & performance: Different regions around the country have different climate patterns 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 (ci) requirements. While stone on honeycomb cladding systems don't have a significant thermal insulation value, they can be designed along 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 standards. This is a complex subject that cannot be addressed briefly and often involves specialized consultants for any given project. There are many thermal efficiency and sustainability parameters, so here we focus solely on LEED points: Some lightweight 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 NFPA 285 is required for certain projects and may also be wanted on projects without such a requirement. Testing should be 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. Some lightweight stone cladding systems and many other alternative cladding systems have met the necessary conditions for acceptance of this important test.

Aesthetics: Owners, developers, and architects have many options in terms of material, color, texture, and aesthetics in general. Even when a natural stone appearance is desired, there are several distinct options including adhered stone (cultured or natural), split-face CMU, dimensional stone, and panelized natural stone. lightweight honeycomb-backed panels can be fabricated with virtually any stone selection including granite, marble, travertine, limestone, sandstone, onyx, and most other quarried 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. Some fabricators of lightweight stone panels fabricate facade systems for specific projects according to approved shop drawings and may include returns of up to 8", giving the impression of colossal stones.

Lead time: Each project is unique and has its own limitations and requirements including project delivery method and lead times for certain systems. For complex, highly engineered systems, a substantial lead time in the order of 16 to 20 weeks (or longer) may be required to cover stone selection and sourcing, design assist service, shop drawings production/approval, fabrication, shipping, and delivery. For projects with short lead time requirements for their cladding systems, other stone cladding solutions may be more feasible than honeycomb-backed panels.

Installation: Generally, panelized systems can be installed much faster than other systems where smaller products or materials must be assembled one by one. Lightweight stone panels can go to 4' x 8' dimensions, and due to their light weight and connection systems, can be installed very efficiently. Also, as rails can be installed on sheathing before the panels are delivered to the job site, it is not uncommon for a crew of two workers to install 30 or more panels in one shift. The key to a successful installation with many rain screen systems, including lightweight stone panels, is to make sure that rails are installed plumb and square, shimmed as needed, and according to approved shop drawings.

A Great Option: We fully share the opinion that no cladding system is right for every construction project. Building design, engineering 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 can be an excellent choice for projects that share some, or all the following characteristics:

- Budget (furnish & install) in the $60's/sf or higher
- Single story to multi-story design to achieve savings in structural framing
- Natural stone aesthetics with variety of finishes
- Any thermal insulation requirements including continuous insulation
- LEED Certification, up to two points
- NFPA 285 flame spread approval
- Natural stone in panels up to 4' x 8' with or without returns
- Fast installation desirable or required
- Unlimited stone types, colors, textures, and finishes
- Lead time of at least 16 to 20 weeks

APCS is an independent representative of TerraCORE Panels (TCP)

More information on TCP at:   https://apcs-sales.com/