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FLOORING PROFILE TO MINIMISE PEAKING

With higher density backsawn hardwoods that are installed in moderate to more humid localities there are concerns with peaking in the floor. This produces a pressure related cupped appearance in a floor that often needs to be sanded out to achieve a flat floor or if more severe has in some instances resulted in the floor being replaced. Following research it is considered that the common 80 x 19mm and 130 x 19mm profiles as outlined in AS 2796 Timber – Hardwood – Sawn and milled products can be redesigned to make the floor less prone to peaking under expansion pressure.

Note that this information sheet has been developed for consideration by flooring manufacturers of higher density timbers mainly in Queensland and New South Wales.

Overview of Peaking

The diagram shows one of the current profiles of a 130 x 19 mm floorboard. When the two shoulders of the board meet at the top of the board there is a small gap at the bottom of the board known as undercut or relief. This minimises any gapping at board edges when a floor is laid.

Screenshot 2022 12 14 at 5.28.23 pm
However, when a floor expands pressure is restrained by the top third of the board only and particularly if the undercut is wide then severe peaking can result. The shape of a board and the appearance of the floor are shown in the photos below. Peaking differs from cupping in that there is no moisture gradient effects.
Screenshot 2022 12 14 at 5.29.31 pm

ATFA profile for reduced peaking

Following research, aspects of the current profile were assessed and a revised profile that is less prone to peaking has been developed. The current AS2796 profile and the ATFA profile for consideration by manufacturers is shown below.

Screenshot 2022 12 14 at 5.31.27 pm
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CUPPING, PEAKING AND CROWNING IN SOLID TIMBER FLOORING

Cupping, peaking and crowning all relate to curvature across the board face – where the board edges are either higher or lower than the centre of the board. In the case of peaking and generally with cupping, the board edges are raised; and with crowning, board edges are lower. There are specific reasons why each of these can occur in solid timber floors. This information sheet will cover the identification of these characteristics, the reasons why they may occur in a floor, and remediation measures that may be needed. At this point, it should be noted that although similar shapes can occur with other flooring types, such as engineered, the causes can be for quite different reasons.
RHNEW

The relationship between relative humidity (RH), moisture content (MC) and board width.

Moisture content and movement

It is important to understand that timber that has been dried for solid flooring still has some moisture in it, and also that board dimensions change throughout the year in response to changes in air relative humidity. 

Under more humid conditions a floor will absorb moisture, raising its moisture content; and in drier lower relative humidity conditions, a floor will release moisture back to the air, with a corresponding reduction in moisture content. When moisture contents increase, boards expand and with a decrease in moisture content they shrink. This principle is shown in the adjacent diagram. 

With seasonal weather changes, we observe movement in our floors and gaps often developing during those drier times of the year and then closing during more humid times.

timbercell

Cell structure as viewed from the board end

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