motion in flooring – Tech Journal

Your blackbutt boards are comparatively large. Motion lengthwise is negligible and may be ignored, however timber motion throughout the grain is proportional to width. Motion can happen if the timber adjustments its moisture content material in situ. In an air-conditioned atmosphere in Melbourne timber merchandise have a moisture content material starting from 7-10% with a mean of 9% (CSIRO Forest Merchandise Publication No. 357). Blackbutt has a “unit motion” issue of 0.37% per 1% change in moisture content material, in accordance with AS 1684.2. Within the worst case state of affairs the place the timber dries by 2%, from 9% to 7%, shrinkage motion can be 282 x 0.37% x 2 = 2.08mm. Rising moisture content material from 9% to 10% would end in enlargement of 282 x 0.37% x 1 = 1.04mm. To make certain that the timber is correctly acclimatised it should be checked at intervals with a moisture meter. On condition that small ranges of motion can nonetheless happen we advocate that slotted fixings are used. Presumably the boards shall be stair treads, screwed to the metal from beneath. On this case one screw gap could be a tight match whereas the opposite ought to be in a slotted gap. By this implies the timber can “slide” a bit of horizontally through the slotted gap, whereas being held right down to the metal vertically.