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Floor dynamics

This section includes information on static deflection and vibration as part of floor design.

Floor dynamics

The stiffness of the floor system affects three aspects of serviceability: short term deflection, long term deflection (creep) and vibration. These factors govern the design of floors more often than strength.

 

 

 

 

Static deflection

A simple stiffness limitation often used is to limit deflections under a 1 kN point load to 1 mm, but this can be overly conservative or quite inadequate in many cases.  

The suggested serviceability deflection limit in AS/NZS 1170.0:2002 is to limit mid-span deflection under a point load to "between 1 and 2 mm." 

A method to assist in the design of floor grid systems to resist concentrated loads is given in AS 1720.1-1997 Appendix E8. 

This methodology allows consideration of the load-sharing effect given by transverse members such as flooring and battens.

 

Vibration

A key design consideration for timber joist floors is that of vibration. 

Some people are bothered by floor vibrations caused by other people walking nearby, or from mechanical causes. 

Satisfactory performance is difficult to assess because different people have different thresholds of perception or tolerance. 

The three main factors that influence perception of movement are:

  • Vibration frequency.
  • Damping in the floor system.
  • Acceleration of the movement.

For design information download the PDF below.

Design information on floor dynamics - Printable PDF

Case study

Remuera House

Remuera House

Richard George, GHD

Key Features
  • The house consists of an elemental two-level rectangular box sitting above a concrete basement level.
  • An external steel structure with a completely glass skin is contrasted by a timber interior that offers a natural warmth.
  • The timber flooring throughout the house is a tongue and groove Victorian Ash that provides a clean-cut elegance.
  • The ceilings consist of a clear stained ply lining with raw LVL ceiling joists left exposed on the intermediate level.
  • Internally, the space is defined by movable panels clad in a Mahogany Sapele crown-cut veneer.
  • The overall effect is a pure architecture with an emphasis on the innate quality of the materials.

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