Checking in decking timber is a serious defect and methods of reducing its severity are required to ensure that wood can compete with alternative decking materials. The first aim of this research was to test the hypothesis that flat sawn Southern pine decking boards with growth rings oriented concave to the exposed surface will develop less severe checking when exposed outdoors than similarly exposed boards whose growth rings are oriented convex to the surface. A second aim was to examine the effects of wood type and three different types of fasteners on checking of boards. Five small decks were constructed each containing Southern pine decking boards with different growth ring orientations and manufactured from wood cut from close to the bark or nearer the centre of logs. Each decking board was fixed to the underlying sub-frame using 3 different types of fasteners, two of which were designed to permit flexural movement of the boards. The decks were exposed outdoors and after 6 months exposure the number and sizes of checks in the boards were assessed. Checks were significantly fewer in number and smaller in boards whose growth ring orientation was concave to the exposed upper surface than in boards whose growth rings were convex to the surface. There was no significant effect of wood type (inner or outer wood) and fastener type on the checking of boards. Orientation of flat sawn boards with growth rings concave to the exposed surface is a simple method of reducing checking of Southern pine decking boards. Further research is required to confirm these preliminary findings using preservative treated timber decking boards exposed for longer periods of time.

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