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The exterior wall assembly of a building typically results from the integration of numerous individual building materials from different manufacturers that are installed by multiple trades and subcontractors. Generally, the specifier selects a basis of design for these wall components,drawn from his or her previous experience and from trusted advisors’ recommendations. The specifier also may include a list of comparable material options from alternate manufacturers. However, when this process reaches the bidding stage, the design team loses control of which products are selected. 

This common practice raises some practical questions. Who is responsible for determining and confirming installed products are code-compliant as a complete exterior wall assembly? Will this particular wall assembly satisfy the more stringent requirements of the 2012 International Building Code (IBC) and International Energy Conservation Code? These codes address multiple and overlapping issues of thermal, moisture, air and fire performance for both the individual materials and specific assemblies of those materials. 

When it comes to fire safety, the IBC references National Fire Protection Association (NFPA) 285: Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components. This is the standard for fire testing in exterior walls when combustible materials, such as foam plastic continuous insulation and water-resistive barriers (WRBs), are components within the wall assembly. 

The stringent and expensive test provides a specific method of determining the flammability characteristics of complete exterior, non-load-bearing wall assemblies/panels. It is intended to evaluate the inclusion of combustible components within wall assembly panels of buildings otherwise required to be of non-combustible construction. As such, the test is designed to emulate the actual fire-resistance performance of the wall assembly in a constructed building.  

NFPA 285 compliance is required for Type I–IV commercial buildings of two stories or more in which exterior wall assemblies integrate combustible claddings, veneers and/or foam plastic insulations. Under the 2012 IBC, WRBs must also be NFPA 285-compliantfor commercial buildings of Type I–IV construction when integrated within wall assemblies exceeding 12 meters (40 feet) in height. Whether cited in the specification or not, the test requires the specific assembly of products and materials intended to be installed in the wall is tested to comply.

Multiple Choice Specifications

The contract documents convey the design intent to comply with code,or more specifically to comply with NFPA 285. Should this responsibility be transferred to a general contractor or sub-trade or a consultant? Who is ultimately liable for determining whether the as-installed assembly has been tested and complies? And, at what project stage is this going to take place: pre- or post-bidding? 

Everyone wants to minimize the risk of a non-compliant assembly being installed. A code enforcement official requiring a test of the as-bid assembly can create additional prohibitive costs and delays. 

This can be extremely complicated, as traditional foam plastic continuous insulation and WRBs may be standalone products with limited, if any,testing as a complete wall assembly. As a result, some manufacturers of these components are attempting to create alliances with various cladding manufacturers to test and offer “typical” code-compliant assemblies.

However, this level of cooperative testing is limited and may not be acceptable to some jurisdictions where attempts are made to simply “blend” individual materials or “similar” assembly test reports together to represent the project specific wall assembly. This also may cause owners and designers to question if the general contractor can provide a wall assembly solution composed of individual materials both compatible with one another and code-compliant, cobbled together from all the possible specified or substituted variations and combinations. That uncertainty is multiplied by separate subcontractors installing the various components of the exterior wall assembly. It is difficult for the project team to have confidence the constructed exterior walls will satisfy the specifications’ requirement of a code-compliant assembly.

Install Tested Assemblies
An exterior insulation and finish system (EIFS) is a prime example of a single-source assembly. Structural wall components, such as exterior framing and sheathing, are already in place at the site before application of the EIFS. One subcontractor then installs the system’s components, often in a single mobilization. All the EIFS components are sourced from a single manufacturer that can offer exhaustive testing, code compliance, and solid warranties on the systems’ quality and performance. The result is a lightweight, high-performance and code-compliant exterior wall assembly.

Modern exterior insulation and finish moisture-drainage systems meet all current building and energy code requirements through their integration of proprietary WRBs, compatible flashings, continuous insulation and integrated detailing for the development of continuous air barriers. Additionally, the systems include a finish surface available in various styles, colors and appearances such as stucco, brick, limestone, granite and metal.

EIFS thicknesses, variations and details are extensively tested and can be installed over a broad range of commonly available structural and non-structural wall substrates in both new construction and renovation. The benefits of this single-source system include:
  • ease of specification;
  • greater control of the bidding and construction processes;
  • simplified contract administration;
  • improved coordination of entire exterior wall components; and 
  • conformance with all aspects of code requirements and architectural design.
Everyone involved in the design and construction process has an interest in ensuring installed exterior wall assemblies match the specifications. As demonstrated, this means the assembly must be tested as a complete system. Regardless of the authority having jurisdiction, the code enforcement official has the right to demand proof of testing compliance in the interest of protecting the public. The licensed design professionals on a project have a similar right to demand compliance with the specifications on behalf of the owner, which is paying for a compliant building all in the interest of protecting the health and safety of building occupants. 

Delivering exterior wall systems through a single-source solution for manufacturing, code compliance and warranty is a proven method of assuring these desired outcomes. In addition to creating a high-performance system, this approach saves time and money for all parties. Perhaps most importantly, it delivers an installed exterior wall system that can readily meet the complete quality and performance standards of the specifications. 

Roland Serino is engineering systems manager for Dryvit. For more information, visit www.dryvit.com

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