FAQ: Design Considerations
Do EIFS have a fire rating?
EIFS alone do not have a fire rating. Testing has been performed to confirm that the fire resistance of an already rated wall assembly is maintained and is not reduced by the addition of EIFS. EIFS have passed the major fire resistance tests that are required by the building codes. EIFS have passed fire resistance, ignitability, intermediate multi-story (NFPA-285), and full scale multi-story corner tests; meeting and surpassing the standards set forth with each test.
Should EIFS be applied below grade?
No. Building codes have criteria for minimum separation of siding materials from grade. EIFS manufacturers generally require that EIFS be maintained not less than 6 inches above finished grade to ensure code compliance.
Is mechanical attachment of EIFS recommended to resist high wind loads?
No. In general, adhesive attachment of EIFS to sound supporting construction provides superior wind load resistance in comparison to mechanical attachment. It is important in an adhesively attached system that the supporting construction is free of surface damage, defects, or contamination. In the case of frame construction, sheathing must be attached with fasteners with the spacing of the fasteners so they are capable of resisting wind loads.
Isn't EIFS easy to crack or break through, meaning it’s not durable?
The systems are designed to be very flexible, which makes them highly crack resistant. When walls expand or contract due to rising or falling temperatures, EIFS are resilient enough to "absorb" building movement and thus avoid the unsightly cracking problems that are so common with stucco, concrete and brick exteriors.
EIFS have passed the stringent Miami-Dade County Hurricane Test, showing no impact against hurricane style weather.
EIFS have passed the major fire resistance tests that are required by the building codes. EIFS have passed fire resistance, ignitability, intermediate multi-story(NFPA-285), and full scale multi-story corner tests; meeting the standards set forth with each test.
What are the limitations for usage of EIFS in high wind load areas?
Independent testing has been performed to determine the ultimate strength of a manufacturer's adhesives to various substrates. The average tensile bond strength was determined to be approximately 20 psi, which converts to 2880 psf. It should be evident that adhesively applied EIFS provides bond strength well in excess of what is needed for virtually any project. The design variables to achieve higher wind load resistance occur within the substrate system and area the responsibility of the project designer.
Is "greenboard" a suitable substrate for EIFS?
No. Gypsum wallboard in compliance with ASTM C 630, often referred to as "greenboard" (because it has a green paper facing on one side), is an interior wallboard commonly used in wet areas such as bathrooms. Suitable gypsum board substrates for EIFS are gypsum sheathing in compliance with ASTM C 1396 (formally C 79), glass-mat gypsum sheathing in compliance with ASTM C 1177 (Dens-Glass Gold® or BPB GlassRoc)), and gypsum fiber panels in compliance with ASTM C1278 (Fiberock® Brand, Aqua Tough™). The sheathing manufacturer's instructions should be followed with respect to handling and installation.
What determines the use and location of a vapor retarder in a wall assembly?
The selection and/or location of a vapor retarder is project specific based on numerous factors including climate, wall components, etc., and as such is a design consideration that is the responsibility of the design professional.