Hardness Ratings Explained – JANKA & AC Rating Systems
Timber floors have provided a basic walking surface in homes across Australia since the earliest days of European settlement. Today they are increasingly used to provide and attractive feature within homes and entertainment venues.
In most cases, appearance is the main consideration on which the selection of a timber flooring product is made. Appearance is influenced by colour, amount of feature or character, width of boards and type of finish applied.
For some heavy use applications consideration should be given to selecting a product of appropriate hardness to suit the application, as improved resistance to denting and abrasion is desirable. For most domestic households a floor rated as moderately hard will be appropriate. When choosing a softer flooring product, which is usually done to achieve a particular aesthetic, then additional care is necessary to prevent damage, such as the removal of foot wear.
One further point of importance is that surface finishes/coatings do not improve the hardness of the floor surface. The hardness of the timber flooring being used, has no correlation with the propensity for its surface finish/coating to scratch, these are two fundamentally different things. Scratches are generally less visible on mat finishes and lighter coloured flooring products.
Janka Hardness Testing
The Janka hardness rating of timber is a measure of its resistance to indentation. The test measures the force (kN) required to press a steel ball of 11.8 mm diameter into the test specimen until the ball has penetrated to half its diameter. There are Janka hardness ratings available for many commonly used timber species. The Janka rating system can also be applied to non solid timber flooring products such as engineered flooring, laminate flooring and bamboo.
The table below provides some examples of species hardness ratings
|Very Hard||Hard||Moderately Hard||Soft|
|Spotted Gum||Brush Box||Tasmania Oak||Radiata Pine|
|Grey Iron Bark||Jarrah||Myrtle||Kauri|
|Strand Woven Bamboo||Kempas||European Oak||Hoop|
Engineered flooring generally has a solid timber species face lamella that is approximately 3mm thick. The hardness of the product is relates to the species used as the lamella and as such the Janka ratings used in the above table still apply.
Bamboo is available as both a laminate and a strand woven product. (Solid Board) In terms of categories the laminated version would be regarded as ‘Hard’ and the Strand Woven as ‘Very Hard’
The Janka hardness test measures the hardness of wood species. It involves measuring the force required to embed an11.28mm (0.444in) steel ball into wood to half its diameter. This method was chosen so that the result would leave an indention 100mm² (0.16sqin) in size. It is one of the best measures of the ability of a wood species to withstand denting and wear. The higher the Janka Rating, the harder the timber is.
|Species||Janka Scale (kN)|
|Bamboo (strand woven)||16.1|
|Sydney Blue Gum||9.0|
|Flooded / Rose Gum||7.5|
|New England Oak||6.1|
Laminate flooring is constructed with a melamine coating over a hardboard core. With these products there is usually an ‘Abrasion Class’ or AC rating associated with them, which relates to their overall resistance to wear. Theses products are suitable for domestic and even commercial applications.
The Laminate Flooring AC Rating
This system ranks laminate flooring products on a simple scale from 1 to 5. The higher the AC rating the better the floor performs. Laminate floors with an AC rating of 1 or 2 are generally to be avoided, as they were not found to withstand scratches, stains or other adverse conditions during testing.
AC1 /21-Moderate Residential
Floors with this rating are suitable only for moderate residential use such as a bedroom or a closet
AC2/22 General Residential
Suitable for “normal residential” applications such as living rooms and dining rooms
AC3 /23 Heavy Residential
Good for all residential applications.
AC3 /31 Moderate Commercial
Suitable for all residential applications plus light commercial such as hotel rooms or small offices
AC4 /32 General Commercial
Use for all residential plus general commercial applications such as offices, boutiques and cafes
AC5 /33 Heavy Commercial
Good for all residential applications plus heavy commercial applications such as public buildings, department stores etc.