What a finished-floor reading actually measures
A resistance reading taken on a completed floor is not the property of one material. It is a system value produced by five elements acting together: the flooring sheet, the adhesive layer, the grounding network, the substrate, and the measurement method.
Until the other four have been measured and excluded, the result cannot be attributed to any single material — including ours.
Point-to-point and resistance-to-earth are different tests
| Test | Current path | Uses the grounding network? |
|---|---|---|
| Point-to-point | Between two electrodes on the surface, through the flooring material | No |
| Resistance to earth | Between a surface electrode and a known earth reference, through the conductive layer, the copper foil and the building earth | Yes |
A low point-to-point reading does not require a complete grounding network: the floor can read low point-to-point while the earth path is open. The two results cannot be substituted for one another, which is why both should be taken at the same time, with the same instrument, under the same conditions.
The direction of the deviation decides where to look
| Reading above the upper acceptance limit | Reading below the lower acceptance limit |
|---|---|
| Moisture in the substrate; adhesive applied too thin or too thick; adhesive not fully cured; copper tape missing or discontinuous; earthing at terminal points only; measurement taken too soon after installation or cleaning | Short circuit through the grounding network; conductive tape in contact with a grounded metal element; wrong electrode arrangement or test voltage |
Two readings that fail in opposite directions rarely share a cause. Ask for the direction before discussing materials.
Six things to collect before re-testing
- Actual readings, with the direction of the deviation and the number of measuring points.
- The as-built grounding detail: a continuous copper grid under the sheet, or earthing at terminal points only — with the tape layout drawing and photographs of the connections.
- Test standard, electrode type, applied load, test voltage, and whether the reported value is a geometric mean.
- Installation date; measurement date and time; temperature and relative humidity at the time of measurement.
- Adhesive consumption against covered area, and the installation specification that was followed.
- Substrate type (concrete or raised access floor) and its moisture reading before installation.
Agree the method in writing before you re-test
Electrode arrangement, applied load and test voltage each change the result. Before a second test, put the following in writing: the standard applied; electrode type and load; the test voltage for resistance-to-earth in the 1 MΩ–100 GΩ range (100 V applies); the number and location of measuring points; and that the reported value is the geometric mean of the individual readings. Do not measure within 24 hours of installation or cleaning — readings taken earlier are not reliable.
What we can state, and what we cannot
We can state the properties of the materials we supply. The conductive adhesive is produced to the antistatic grade of JC/T 550-2019, with a specified maximum of 3 × 105 Ω, and the delivered batch is verified by the adhesive manufacturer's test report. That report belongs to the adhesive manufacturer. It is a material test, not a test of a finished floor, and it is not presented as one. For the copper foil we can state the physical specification and its calculated linear resistance.
We cannot state a finished-floor resistance value in advance. The finished value depends on the substrate, the adhesive film, the grounding network and the test method on site, and it has to be measured there. A finished-floor figure quoted without those four inputs cannot be relied on.
How a disputed reading is handled
Joint verification: the installer and our technical team measure together, with the same instrument, under the same conditions, and both sides confirm the result. Reference samples of the adhesive and the tape from the same batch are kept, so that they can be tested in parallel if needed.
Related reading: ESD anti-static flooring guide · ESD flooring · Conductive adhesive · Test reports
Frequently asked questions
Can a low point-to-point reading prove that the floor is earthed?
No. Current in a point-to-point test travels through the flooring material and does not pass through the grounding network. A floor can read low point-to-point while the earth path is open, so both tests are needed.
Why can't the adhesive be identified as the cause first?
Because a finished-floor reading is a system value. The adhesive is one of five contributors; until the substrate, the grounding network and the test method have been checked, there is no basis for attributing the result to a single material.
How soon after installation can the floor be measured?
Not within 24 hours of installation or cleaning. Readings taken earlier are not reliable and should not be used for acceptance.
Why a geometric mean rather than an arithmetic average?
Resistance values are spread over orders of magnitude, so an arithmetic average is dominated by the highest readings. The reported value should be the geometric mean of the individual measurements, and the method should be agreed in writing before testing.
Do you publish a guaranteed finished-floor resistance?
No. We state material properties and installation requirements. The finished value depends on the substrate, the adhesive film, the grounding network and the on-site method, and it has to be measured on the finished floor.