An insulating support surface is used beneath a flooring sample when the applicable test procedure calls for it, such as during laboratory qualification. It is separate from the materials that make up the flooring system.
For example, an adhesive-installed tile sample includes the tile, adhesive, grounding system and intended substrate. That complete assembly is placed on the insulating support surface for testing. The insulating support helps electrically isolate the flooring sample from the surface beneath it, reducing unintended current paths that could affect the test results.
The required electrical properties of that support surface depend on the test method. The table below compares the values specified by STM7.1-2020, STM97.1-2025, STM97.2-2016 and ESD TR53-01-22.
The cited electrostatic discharge (ESD) documents include standard test methods (STM) and a technical report (TR). The ANSI/ESD methods are approved by the American National Standards Institute (ANSI); ASTM D257 is published by ASTM International.
Support surface values by document
| Document | Surface resistivity per ASTM D257 | Surface resistance per ANSI/ESD STM11.11 |
|---|---|---|
| ANSI/ESD STM7.1-2020 | Greater than 1.0 × 10¹¹ ohms/square | Greater than 1.0 × 10¹⁰ ohms |
| ANSI/ESD STM97.1-2025 | Greater than 1.0 × 10¹¹ ohms/square | Greater than 1.0 × 10¹⁰ ohms |
| ANSI/ESD STM97.2-2016 | Greater than 1.0 × 10¹³ ohms/square | Greater than 1.0 × 10¹² ohms |
| ESD TR53-01-22 | Greater than 1.0 × 10¹³ ohms/square | Greater than 1.0 × 10¹² ohms |
In each document, the values apply to a planar (flat) surface when it is used for flooring sample support; either listed method may be used, provided its corresponding threshold is met. ESD TR53-01-22 is an informational ESD Association technical report, so its support surface values and checks are the report’s own procedure rather than requirements with the authority of a consensus standard.
Alternate checks and conditions by document
ANSI/ESD STM7.1-2020
For test methods using 2.27 kg, 63.5 mm electrodes, STM7.1-2020 permits verifying the support surface by measuring point-to-point resistance with the electrodes spaced at least 150 mm apart (edge-to-edge). A point-to-point resistance at least 10 times the measured item’s upper limit (one order of magnitude higher) is required.
ANSI/ESD STM97.1-2025
STM97.1-2025 permits verifying the support surface by measuring the point-to-point resistance of the material with the resistance measurement electrodes spaced at least 150 mm apart (edge-to-edge). The support surface must be measured in the same humidity conditions at which the material will be tested, and it must be larger than the flooring sample.
ANSI/ESD STM97.2-2016
For test methods using 2.27 kg (5 lb), 6.35 cm (2.5 inch) electrodes, STM97.2-2016 permits verifying the support surface by measuring point-to-point resistance with the electrodes spaced at least 15 cm (6 inches) apart (edge-to-edge). A point-to-point resistance at least one order of magnitude greater than the upper limit of the item being measured is required.
ESD TR53-01-22
For test methods using 2.27 kg, 63.5 mm electrodes, TR53-01-22 permits verifying the support surface by measuring point-to-point resistance with the electrodes spaced at least 150 mm apart (edge-to-edge). For test methods using concentric ring electrodes, it permits measuring the surface resistance of the material. In either check, the measured resistance must be at least one order of magnitude greater than the upper limit of the measured item.
Is the support surface the floor substrate?
No. Under ANSI/ESD STM97.1-2025, the flooring sample support surface is not the substrate layer of the flooring sample. The substrate belongs to the flooring assembly being tested. ANSI/ESD STM7.1-2020 and STM97.1-2025 both require the flooring system sample to be representative of and include all the system components as they would be used in an installation. For tiles installed with an adhesive, the test includes the tile, the appropriate adhesive, the grounding system, and the substrate that would be used.
Frequently Asked Questions
No. ANSI/ESD STM7.1-2020 and STM97.1-2025 specify surface resistivity greater than 1.0 × 10¹¹ ohms/square per ASTM D257 or surface resistance greater than 1.0 × 10¹⁰ ohms per ANSI/ESD STM11.11. STM97.2-2016 and ESD TR53-01-22 specify the higher values of greater than 1.0 × 10¹³ ohms/square or greater than 1.0 × 10¹² ohms, respectively. These values apply to planar surfaces used for flooring sample support; TR53 is an informational technical report.
No. ANSI/ESD STM97.1-2025 distinguishes the support surface from the flooring sample’s substrate layer. STM7.1-2020 and STM97.1-2025 require the flooring sample to include the intended installation components, including the substrate that would be used for adhesive-installed tiles.
ANSI/ESD STM97.1-2025 requires the flooring sample support surface to be measured in the same humidity conditions at which the material will be tested.