TECHNICAL INSIGHTS
TECHNICAL INSIGHTS The articles featured in Technical Insights are to prompt thought and discussion to assist our members' question and evaluate their understanding of the technical requirements of Australian Standards and other national/international source material. Technical Insights is to intended to provide background information, a different viewpoint, a perspective from an individual with lived experience of disability or to prompt further discussion and/or research by you as an access professional.
by Howard Moutrie
TIMBER DECKING
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ne of the most common questions asked relates to the accessibility of timber decking and, in particular, the gaps between the boards. Typically, the requirements for grates are applied in the absence of any other guidance. I thought it would be worthwhile to discuss this issue. The gaps between the timber decking boards are provided principally to accommodate expansion and contraction of the timber but also aid in the extraction of surface water. I note that timber decking is not always timber, and the new synthetic products behave differently. The recommended spacing of the decking boards varies depending on the type of timber, the width of the boarding and the location. The variation is from 3 -7mm. The variations occur due to the properties of the timber, some timbers expand more than others, the size of board, a wider board will expand more than a narrower board and the location, the timber is more likely to expand and contact to a greater degree when the environmental conditions are extremely wet and hot, for example in far north Queensland. It is also important to recognise that timber decking may also include wide and thick timber boards in locations such as a jetty. Under most conditions a gap of 5-6mm is sufficient for standard timber decking while synthetic wood decking is 5mm. Large boards on a jetty for example may need 10-15mm spacing as 42
they also may need to address cupping and twisting in addition to expansion. I would suggest that we say that the maximum gap between decking boards is to be 6mm as this covers the majority of situations. So, in terms of accessibility, what should we consider acceptable. It is worthwhile to reference the requirements for grates and pavers. I would consider that a max 6mm gap with a maximum surface level difference between adjacent boards of 3mm. This is consistent with the existing requirements for other surfaces and meets the requirements for standard timber decking. Larger decking boards, over a 150mm wide may require an increased gap. The gap may be increased to a maximum of 13mm, based on the requirements for grates, provided that, where the gap exceeds 8mm the boards shall run transverse to the direction of travel.
VISUAL IDENTIFICATION OF GLASS Clause 6.6 of AS 1428.1 provides the requirements for “vision strips” as I like to call them. One of the requirements is that the strip provides a 30% luminance contrast with the surface on the other side. I have commented, previously, that this requirement hasn’t been well thought through, particularly with respect to the testing of the installation to verify the luminance contrast. The strip is viewed against the background, through the glass, but is this how it is intended to be tested? If this is the case, then the LRV reading of the background will be affected by
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