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Oriented strand board (OSB) is a type of engineered wood, formed by adding adhesives and then compressing layers of wood strands (flakes) in specific orientations. It was invented by Armin Elmendorf in California in 1963. [ 1 ]
[citation needed] At 3 ⁄ 8 inch (9.5 mm) thick, mahogany three-ply "wiggle board" or "bendy board" come in 4 by 8 feet (1.2 m × 2.4 m) sheets with a very thin cross-grain central ply and two thicker exterior plies, either long grain on the sheet, or cross grain. Wiggle board is often glued together in two layers once it is formed into the ...
The board can be sheet metal, fibre cement, magnesium oxide board (MgO), plywood or oriented strand board (OSB), and the core can either be expanded polystyrene foam (EPS), extruded polystyrene foam (XPS), polyisocyanurate foam, polyurethane foam, or be composite honeycomb (HSC).
Plywood and OSB typically have a density of 560–640 kg/m 3 (35–40 lb/cu ft). For example, 9.5 mm (3 ⁄ 8 in) plywood sheathing or OSB sheathing typically has a surface density of 4.9–5.9 kg/m 2 (1–1.2 lb/sq ft). [51] Many other engineered woods have densities much higher than OSB.
The shingles produced in 1939 were sufficient to cover more than 1,000,000 dwellings, assuming an average size of 10 squares per roof. In two surveys of roofing materials in 20 Eastern States, - made during 1938, the kinds of roofing materials on 20,841 dwellings along 4,038 miles of highway were tabulated.
For softwoods, the common classes are (in increasing strength) C16, C18, C24, and C30. There are also classes specifically for hardwoods and those in most common use (in increasing strength) are D24, D30, D40, D50, D60, and D70. For these classes, the number refers to the required 5th percentile bending strength in newtons per square millimetre.
A study by Ducker International in 2005 identified the average cost per year of a metal roof to be US$3.2 per square metre ($0.30/sq ft) while single-ply roofs stood at $6.1/m 2 ($0.57/sq ft) and built-up roofing at $4.0/m 2 ($0.37/sq ft).
The formed sheets are cold-compressed to reduce thickness and make them easier to transport. Later, they are compressed again, under pressures between 2 and 3 megapascals (290 and 440 psi) and temperatures between 140 and 220 °C (284 and 428 °F) to set and harden the glue.