Replacement greenhouse staging was needed, with dimensions about 90 cm high, 90 cm wide and 35 cm deep. I built some using purchased wood.
Materials
The choice and cost of wood influenced the design. Champion Timber offered untreated planed redwood planks at 94 mm by 15 mm at £ 9.61 a metre. B&Q offered treated rough sawn whitewood spruce at 100 mm by 22 mm (the minimum thickness) at £ 3.04 a metre. It also came as ‘one by two’ (22 mm by 50 mm) ‘sticks’ at £ 2.48 per metre. A thickness of 22 mm was tolerable and the relative cost attractive, so I used the rough sawn wood.
The rough sawn wood came in 1.8 m lengths, convenient for a 90 cm width and height. I bought three 125 mm wide planks, two 100 mm wide planks and six sticks.
Design
The basic design was three slatted shelves, comprised of planks, resting on horizontal struts between four legs.
The actual length of the planks differed, slightly, from 1,800 mm. The shortest plank, halved, determined the actual width of the staging. Other planks were cut into segments of the same length. The wider plank was centred between the narrower planks. For the second and third shelves, rectangular notches (slightly larger than the cross-section of the legs) were cut out of the four corners.
The almost-square legs of the staging would be formed by two sticks back-to-back (44 mm by 50 mm). Each leg could be cut from a single stick, with a short length remaining. That short length would also be used.
Three sets of horizontal struts could be cut from a single stick. The second longest stick (together with the longest) would determine the depth of the staging, by cutting it first into thirds and then cutting a third into two pieces, one 100 mm longer than the other. With a kerf of 2.6 mm, in practice, the depth of the staging was about 349 mm.
For the second and third shelves, the narrower planks were supported both by the horizontal struts and additional 50 mm squares cut from the remaining short lengths from the sticks and placed against the inside of the legs.
Construction
The rough sawn timber often had one face that was better quality than the other. The poorer quality faces were placed on the underside. The planks with the best faces of all were used for the top shelf. After construction, exposed faces were sanded to avoid splinters.
Care was taken that similar pieces of stick were cut to the same length, so that the staging would be square, on assembly. The width and thickness of the stick, although rough sawn, was measured to be broadly consistent.
Pieces were joined with PVA wood glue, clamping until it had fully cured. In addition, the horizontal struts were screwed to the legs and the planks were screwed to the horizontal struts, using two 35 mm by 3.5 mm screws at each end. The square supports were also screwed to the legs with two screws.
A metal cross-brace (IKEA, £ 2) was used to increase the resistence of the final staging to any horizontal shear forces during use.