National foreword

This British Standard is the UK implementation of ISO 24323:2023.

The UK participation in its preparation was entrusted to Technical Committee B/518, Structural timber.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2023.

Foreword

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This document was prepared by Technical Committee ISO/TC 165, Timber structures.

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 www.iso.org/members.html.

Introduction

Timber floors are known to be prone to producing high level of vibration caused by human activities due to the light-weight nature of these systems. As a result, it is critical that the timber floor design process takes into account vibrational serviceability. In the past, static deflection check indirectly provided some degree of control, but it is not a complete solution to the vibration problem. Two ISO publications have been developed over the last few years under the auspices of ISO/TC 165. The first publication, ISO 18324^[¹^], is intended for testing of floor response parameters for the purpose of evaluating vibrational serviceability of the floor. The second publication is ISO/TR 21136^[²^], which provides guidelines for developing floor vibration performance criterion.

Annexes A and B recommend limit values for coupled and decoupled criteria respectively. The calculation equations presented herein are based on the assumption that the floor system has a single span and simple support conditions.

This document provides flexibility for individual jurisdictions to develop their own performance levels within the same performance criterion framework using the procedure described in ISO/TR 21136^[²^], and for using other models to calculate the fundamental natural frequency and 1 kN static deflection if desired.

1 Scope

The design method provided in this document addresses vibration induced by walking action of occupants and covers the following timber floor systems:

Light frame floors built with timber joists spaced at a distance of no more than 610 mm with a layer of structural wood-based subfloor that is connected to the joists using mechanical fasteners or adhesive. The area density of a bare light frame floors without a screed (topping) and ceiling is not greater than 25 kg/m². Figure 1 shows such a light frame floor.
Mass timber floors built with mass timber panels such as cross laminated timber (CLT).

This document consists of three elements:

a baseline vibrational serviceability design criterion for timber floors using fundamental natural frequency and 1 kN static point load deflection as the design parameters including two types of design criteria, coupled and decoupled criteria;
equations for calculating the design parameters;
guidelines for the design values of the physical and mechanical properties of floor components.

The design method is based on the assumption that the floor system has a single span and simple support conditions.

2 Normative references

3 Terms and definitions

4 Baseline timber floor vibrational serviceability design criterion

5 General models for calculating f and d_1 kN

6 Simplified calculation procedures for light-frame timber joisted floors

6.1 Floor construction

6.2 Calculation of first natural frequency and static deflection under a 1 kN load at floor centre

6.3 Effective composite bending stiffness, D_ef

6.4 Transverse system stiffness factor, K_t

7 Simplified calculation procedures for mass timber floors

7.1 Floor construction

7.2 Calculation of first natural frequency and static deflection under a 1 kN load at floor centre

8 Design values of floor components

Bibliography

BS ISO 24323:2023

Timber structures. Design method for vibrational serviceability of timber floors

Current

Published:

31 Dec 2023