What Is ASTM E1745: Understanding the Standard and Its Classifications

Demystifying the Key Requirements and Performance Metrics for Effective Below-Slab Vapor Retarders

ASTM (American Society for Testing and Materials) E1745 is the Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill under Concrete Slabs. This standard requires products undergo conditioning testing designed to simulate in-service (under-slab and installation) conditions, and it classifies vapor retarders based on their tensile strength, puncture resistance, and water vapor permeance ratings.

ASTM E1745 Classifications

ASTM E1745 is the standard for flexible sheet membranes to be used as vapor retarders for on-ground and below-grade slab applications under concrete. It requires that applicable products be tested to determine their tensile strength, puncture resistance, and water vapor permeance ratings, this final metric being measured both before and after undergoing mandatory conditioning testing.

• Permeance refers to a product’s ability to resist vapor migration and is measured in perms, which is defined in the US as one grain of water vapor per hour, per square foot, per inch of mercury (pressure differential) [gr/(ft²*hr*in-Hg)]. The lower the permeance rating, the better protection from water vapor diffusion the product provides. Vapor retarders that are subjected to the ASTM E1745 standard must be rated to 0.1 perms or less, though industry experts point to 0.01 perms for vapor barriers.
• Tensile strength is measured in pounds (force) per inch, and is tested by applying stress to the material that simulates some of the loads a vapor retarder will face during installation.
• Puncture resistance addresses how well the vapor retarder material withstands impact with blunt objects. Vapor retarders are subjected to impact by a rounded falling dart, which is intended to roughly simulate some of the hazards of construction.

Once these measurements are taken, the vapor retarder is given one of the following three classifications:

• Class A - Maximum of 0.1 perms, minimum 45 lb/in tensile strength, 2200 grams puncture resistance.
• Class B - Maximum of 0.1 perms, minimum 30 lb/in tensile strength, 1700 grams puncture resistance.
• Class C - Maximum of 0.1 perms, minimum 13.6 lb/in tensile strength, 475 grams puncture resistance.
  

ASTM E1745 Test Methods

The required tests mentioned above utilize specific standard test methods:

• E154: This is where all of the conditioning testing referenced in E1745 is found. E1745 cites E154 sections 8, 11, 12 and 13 within (among others). These sections simulate many of the conditions the vapor retarder will face while in service.
• D882: This method tests the tensile strength of a vapor retarder.
• D1709: This test uses free-falling darts to test the impact puncture resistance of a vapor retarder.
• E96/E96M: This test uses a wet cup method or dry (desiccant) cup method to test water permeance. 
• F1249: This test measures the water vapor permeance using an infrared sensor.  

Considerations When Choosing a Class of Vapor Retarder

Once you have a clear understanding of ASTM E1745, choosing a classification of vapor retarder for your project should be much simpler. However, there are drawbacks to the standard that need to be taken into account. For instance, maximum permeance rating requirements don’t change by class. Choosing a Class A vapor retarder does not necessarily guarantee sufficient protection; you may need to specify a permeance rating well below 0.1 perms. Also, ASTM D1709, while useful for determining puncture resistance, simulates only impact resistance and not the push-through or point loads caused by rocks or other sharp objects.

4 critical items to verify with the manufacturer prior to purchasing a vapor retarder are:

1. That the selected product achieves the classification and all other performance requirements specified. A lower permeance or higher tensile strength may be required than is specified by the ASTM E1745 class rating.
2. That the material has been subjected to conditioning testing and maintains the specified permeance rating.
3. If specified, that certification of independent testing and/or test witnessing is made available. For example, ASTM E1745 section 9.3 requires that a summary of tests, testing date(s), testing or witnessing laboratory, and results are provided by the manufacturer.
4. That testing was conducted for each test on a single roll, and that the roll tested was indicative of production material (i.e. material sold to the end user).This is a requirement of ASTM E1745 Section 8.1.

The quality of any construction project depends on three simple factors: good design, superior workmanship, and quality products. A product that also incorporates these principles will prove to have durability and functionality that exceed the design requirements. ASTM E1745 is an extremely useful standard for any specifier of under-slab vapor retarders and barriers. While it’s not a complete or comprehensive tool when creating specifications, it’s still an important component.

Industry Changes: 2021 International Residential Code

Under the 2021 International Residential Code (IRC^®), it is required that water vapor retarders used beneath concrete floor slabs conform to the ASTM E1745 Class A specifications. This inclusion in the residential code emphasizes the necessity for higher-performance materials that offer more robust vapor protection at the first side of the home. Adhering to these requirements is not only crucial for meeting building codes but also for helping provide homeowners with a healthy and durable living environment. 

Is Your Construction Project Bogged Down by Complicated ASTM Standards?

At Stego®, we understand that navigating ASTM standards, like E1745, can be overwhelming and confusing. But you don't have to tackle it alone! We take pride in ensuring our experts are up to date on industry standards and regulations so that they are ready to guide you through every question and challenge.  

Contact us today, and let's make your project a success with the right guidance on ASTM standards.  

Editor's note: This blog post was initially written by Dan Marks, our former Technical Director at Stego, in October 2016 and has been revised to stay up-to-date.