ISO 23999:2025

Resilient floor coverings - Determination of dimensional stability and curling (vertical deformation) after exposure to heat

This document specifies methods for determining dimensional stability and curling (vertical deformation) of resilient floor coverings in all forms (e.g. of sheets, tiles, panels, planks or in rolls) after exposure to either heat or after reconditioning, or both.

Revêtements de sol résilients — Détermination de la stabilité dimensionnelle et de l’incurvation (déformation verticale) après exposition à la chaleur

Le présent document spécifie une méthode de détermination de la stabilité dimensionnelle et de l’incurvation des revêtements de sol résilients, sous forme de rouleaux, de dalles ou de lames, après exposition à la chaleur.

General Information

• Status: Published
• Publication Date: 25-Nov-2025
• ICS: 97.150 - Floor coverings
• Technical Committee: ISO/TC 219 - Floor coverings
• Drafting Committee: ISO/TC 219/WG 2 - Resilient floor coverings
• Current Stage: 6060 - International Standard published
• Start Date: 26-Nov-2025
• Due Date: 05-Mar-2026
• Completion Date: 26-Nov-2025

Relations

• Consolidates: ISO 8893:2021 - Forestry machinery - Portable brush-cutters and grass-trimmers - Engine performance and fuel consumption
• Effective Date: 23-Mar-2024
• Revises: ISO 23999:2021 - Resilient floor coverings - Determination of dimensional stability and curling after exposure to heat
• Effective Date: 27-Jan-2024

Overview

ISO 23999:2025 - "Resilient floor coverings - Determination of dimensional stability and curling (vertical deformation) after exposure to heat" specifies standardized test methods to assess how resilient flooring (sheets, tiles, panels, planks or rolls) reacts to heat. The standard defines procedures for measuring dimensional stability (linear change) and curling (vertical deformation) after heat exposure and optional reconditioning. It replaces the 2021 edition and includes clarified measurement approaches and new informative annexes for result calculation.

Key technical topics and requirements

• Scope and test principle
  • Measures dimensional change and vertical deformation of resilient floor coverings after heat exposure and reconditioning.
  • Tests use three specimens measured before and after treatment.
• Specimen types
  • Applicable to sheets, rolls, tiles, panels and planks; preparation steps differ by form.
• Apparatus and oven requirements
  • Thermostatically controlled, ventilated oven with uniform temperature ±2 °C.
  • Specimens must be positioned so heating elements do not radiate directly; support plates must sit >50 mm from oven walls and >100 mm from ceiling/base.
• Support plates
  • Metal plates (e.g., aluminium or stainless steel), thickness 2.0 mm ±0.5 mm, smooth and flat.
• Measurement devices and resolution
  • Curling (vertical deformation): devices with minimum resolution ±0.1 mm (laser, optical, tactile gauges).
  • Linear dimensional change: devices with minimum resolution ±0.02 mm (optical bench, callipers, block and dial gauge setups).
  • Includes guidance on scoring marks, rigid steel plate use, and the “block and dial gauge apparatus” for tiles/planks.
• Terminology
  • Defines machine direction (MD) and across machine direction (AMD); MD/AMD can be assigned arbitrarily when unknown.
  • Curling conventions: concave (outer-edge uplift = positive) and convex (centre dome = negative).
• Procedure
  • Initial measurement → heat exposure → reconditioning (if applicable) → final measurement.
  • Annex A and B provide measurement and calculation guidance.

Practical applications and who uses it

ISO 23999:2025 is used by:

• Flooring manufacturers for product development and quality control.
• Independent testing laboratories to provide consistent test data.
• Specifiers, architects, and procurement teams assessing material suitability for heated environments (e.g., commercial fit-outs, underfloor heating situations).
• Installers and compliance officers verifying product claims and conformity to performance requirements.

Benefits include reproducible test results, improved product specification, and reduced installation failures related to thermal distortion.

Related standards and context

• Prepared by ISO/TC 219 (Floor coverings) in collaboration with CEN/TC 134.
• Includes informative Annex A (measurement of dimensional change due to heat) and Annex B (calculation and expression of results).

Keywords: ISO 23999:2025, resilient floor coverings, dimensional stability, curling, vertical deformation, heat exposure, oven requirements, block and dial gauge, optical bench, flooring test methods.

Standards Content (Sample)

International
Standard
ISO 23999
Fourth edition
Resilient floor coverings —
2025-11
Determination of dimensional
stability and curling (vertical
deformation) after exposure to heat
Revêtements de sol résilients — Détermination de la stabilité
dimensionnelle et de l’incurvation (déformation verticale) après
exposition à la chaleur
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
4.1 General .2
4.2 Dimensional stability .2
4.3 Curling (vertical deformation) .2
5 Apparatus . 2
5.1 Oven.2
5.2 Support plates .3
6 Measuring devices . 3
6.1 Measurement devices for determination of curling (vertical deformation) .3
6.2 Measurement devices for determination of linear dimension changes .3
6.2.1 General .3
6.2.2 Scoring device .3
6.2.3 Rigid steel plate .3
6.2.4 Block and dial gauge apparatus (for tiles and planks) .4
7 Test specimens . 6
7.1 Specimen preparation from sheet or roll material .6
7.2 Specimen preparation from tiles and planks .8
8 Conditioning . 8
9 Test procedure . 8
9.1 Initial measurement .8
9.1.1 Curling (vertical deformation) .8
9.1.2 Linear dimensions . . .9
9.2 Heat exposure.10
9.3 Reconditioning.10
9.4 Final measurement .10
9.4.1 Curling (vertical deformation) .10
9.4.2 Linear dimensions . . .10
10 Calculation and expression of results .11
10.1 Curling (vertical deformation) .11
10.2 Dimensional change .11
11 Test report .12
Annex A (informative) Measurement of dimensional change due to heat .13
Annex B (informative) Calculation and expression of results . 14

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see http://www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
http://www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization
(WTO) principles in the Technical Barriers to Trade (TBT), see http://www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 219, Floor coverings, in collaboration with the
European Committee for Standardization (CEN) Technical Committee CEN/TC 134 Resilient, textile, laminate
and modular mechanical locked floor coverings, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This fourth edition cancels and replaces the third edition (ISO 23999:2021), which has been technically
revised.
The main changes are as follows:
— revision of terms and definitions;
— clarification on the deviation between devices used for either sheet or roll, or both, materials and
rectangular shaped elements (squared tiles or long panels);
— inclusion of an explanation on the use of the so called “block and dial gauge apparatus” and minor changes
to the figures and a new figure was added;
— inclusion of description of the preparation distinguishing sheet, roll materials and rectangular shaped
elements (squared tiles or long panels);
— detailed calculation and expression of results can be found in new Annex B.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at http://www.iso.org/members.html.

iv
International Standard ISO 23999:2025(en)
Resilient floor coverings — Determination of dimensional
stability and curling (vertical deformation) after
exposure to heat
1 Scope
This document specifies methods for determining dimensional stability and curling (vertical deformation)
of resilient floor coverings in all forms (e.g. of sheets, tiles, panels, planks or in rolls) after exposure to either
heat or after reconditioning, or both.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
dimensional stability
ability of a resilient floor covering to retain its original linear dimensions after exposure to heat, determined
by measuring the linear dimensional change in machine direction or across machine direction
Note 1 to entry: Retaining original linear dimensions includes no elongation or shrinking.
3.2
curling
vertical deformation
vertically concave (+) or convex (-) deformation from the horizontal
3.3
concave deformation
type of curling (vertical deformation) appearing as uplifted top surface at the outer edge of the specimen;
given as positive value (+)
3.4
convex deformation
type of curling (vertical deformation) appearing as uplifted, domed top surface in the centre of the specimen;
given as negative value (-)
3.5
machine direction
MD
direction parallel to the length side of a floor covering manufactured in a continuous process
Note 1 to entry: For rectangular or squared cut specimens (e.g. tiles and planks) where the machine direction cannot
be determined, the direction of MD can be arbitrarily assigned for the test to enable differentiation from across
machine direction (AMD).
3.6
across machine direction
AMD
direction across to the length side of a floor covering manufactured in a continuous process
Note 1 to entry: For rectangular or squared cut specimens (e.g. tiles and planks) where the across machine direction
cannot be determined, the AMD can be arbitrarily assigned for the test to enable differentiation from machine
direction (MD).
4 Principle
4.1 General
Three test specimens are initially measured and then placed in an oven at an elevated temperature
which can cause dimensional changes and curl. After a specific period in the oven and subsequent time of
reconditioning, dimensional stability and the stability against vertical deformation (curling) are measured
again on the same test specimens.
4.2 Dimensional stability
The relative change in linear distance between the same marks or same specific locations of the top surface
layer of a test specimen, measured after exposure to a heat treatment and reconditioning. Depending on
the size of the specimen and the structure of the surface, different measuring devices can therefore be
appropriate.
As a special interest case, the change of linear dimensions can be determined on hot test specimens, meaning
before reconditioning. As this does not affect the measurement of dimensional stability and curling, it may
be determined as an intermediate result on the same test specimens (see Annex A).
4.3 Curling (vertical deformation)
Curling is measured at the highest peaks of the test specimens, possibly occurring after the specified heat
treatment in an oven at an elevated temperature and reconditioning in a normal conditioned climate.
An initial vertical deformation of the test specimen (before the exposure to heat) may be measured (see
Figure 7).
5 Apparatus
5.1 Oven
The oven shall be thermostatically controlled and ventilated, capable of being maintained at a uniform
temperature with maximum deviations of ±2 °C.
The oven shall allow for specimens to be placed inside in a way that ensures that radiation from the heating
elements does not directly reach the test specimens or support plates (see 5.2). Therefore, the distance
between the support plates and the vertical walls of the oven shall be more than 50 mm and the vertical
distance between the support plates and between the plates and the oven ceiling and base shall be more
than 100 mm.
5.2 Support plates
The support plates on which the specimens will be placed for the test shall be of metal, e.g. aluminium or
stainless steel, and 2,0 mm ± 0,5 mm in thickness. The overall length and width of the support plates shall
be of dimensions larger than the test specimen. Ensure that the support plates are kept smooth and polished
so that surface friction does not interfere with free shrinkage or growth of the test specimens. The plates
shall be flat and free of convex or concave distortion and fully support the specimen (e.g. a wire rack support
plate is not acceptable.).
6 Measuring devices
6.1 Measurement devices for determination of curling (vertical deformation)
The measuring equipment can be any appropriate apparatus or device capable of measuring small distances
vertical from the support plate (see 5.2) with a minimum resolution of the display accuracy or graduation of
±0,1 mm and without influencing the test specimens by any kind of load from the test device itself.
This may include:
— a laser measuring device;
— other optical measuring devices;
— tactile measuring devices (e.g. pillar-mounted drop gauge device, feeler gauges or a micrometer).
6.2 Measurement devices for determination of linear dimension changes
6.2.1 General
All used measuring equipment shall measure with a minimum resolution of the display accuracy or
graduation of at least ±0,02 mm.
The measuring equipment may include:
— an optical bench for non-contact dimensional measurements between two marks on the top surface (for
example scores which are carefully made in the surface); or
— callipers; or
— a block and dial set-up (see 6.2.4) as shown in Figures 2, 3 and 4 for tactile measurement at the outer edge
of the specimen top layer.
For many types of optical benches, ensure that the test specimen is properly seated against the base
horizontal index guide when a specific measurement is being taken, otherwise test specimens with concave
or convex edges can be read incorrectly.
For ready shaped floor covering elements (e.g. tiles and planks), the block and dial gauge apparatus is
appropriate. For test specimens prepared from sheet or roll material, equipment shall be used which take
measures from the top surface.
6.2.2 Scoring device
For measurements with an optical bench (see 6.2.1) a scoring device, e.g. a single edge razor blade, scalpel
or scribe point, may be used to make marks in the top surface of test specimens made from sheet or roll
material or optionally tiles and planks.
6.2.3 Rigid steel plate
Optional auxiliary device to help flatten test specimens from sheet or roll material or optionally-tiles and
planks with a concave deformation or with a convex deformation. A rigid plate of steel, squared and finished,

of dimensions 240 mm × 240 mm with holes to see the measuring marks (examples are shown in Figures 1
and 6) on the top surface of the specimens. If larger format specimens are tested, then the rigid plate should
be of commensurate size and configuration.
Dimensions in millimetres
Figure 1 — Rigid steel plate
6.2.4 Block and dial gauge apparatus (for tiles and planks)
6.2.4.1 General
Test device consisting of a support that is large enough to fit the test specimen and with a lay-on edge (block)
to be used with a measuring device (for example a dial gauge, see Figures 2, 3 and 4).
6.2.4.2 Square standard template
A standard template may be used together with the block and dial gauge apparatus (see 6.2.4.1) for
determination of deviations in size between the template and a product or a specimen. Figure 2 shows an
example of a block and dial gauge apparatus with the possible use of standard templates in four different
sizes and possible positions of the measuring devices to also determine straightness and squareness.
A square standard template has the nominal side length of a product or a test specimen and should be
rectangular. The deviations from the template sizes before and after heat exposure can show the linear
dimensional changes due to the heat influence.
NOTE 1 A standard template calibrated for straightness, squareness, and length with regard to the nominal sizes of
a product can be useful for a quick measurement (e.g. for in-house production monitoring).
NOTE 2 The calculation of the dimensional changes shown in Clause 10 do not refer to the measuring method with
the use of a template.
6.2.4.3 Shim or spacer block
An auxiliary device to bridge the gap between the stop (edge) of the block and dial gauge apparatus (see
6.2.4.1) and a specimen whose dimensions are such that the dial gauges may not be in direct contact with
the specimen as shown in Figures 3 and 4. A rigid steel plate, square and with parallel sides, which serves as
a filling for the free space when it is required for the use of the block and dial gauge device.
NOTE Specimens (flooring products) can have different widths which can make it necessary to use shim or
spacer blocks with different sizes or a combination of two or more spacer blocks. As the measurement is a relative
measurement of a change in dimension, the spacer block can be without calibration provided that the spacer block is
placed in exactly the same position and orientation between measurements.

Dimensions in millimetres
Key
1 edge 1
2 edge 2
3 edge 3
4 edge 4
A template 610 mm × 610 mm
A template 508 mm × 508 mm
A template 305 mm × 305 mm
A template 229 mm × 2
...