Structural Flakeboards and Composites 2909 



alent to those specified in a Federal Housing Authority (FHA) Memorandum 

 Approval. Waferboard continued to be used under the FHA Memorandum 

 Approval until 1975 when a formal Materials Release was issued. Also during 

 the years 1972-1975, West Coast model code approval was obtained for orient- 

 ed-strand board, which has higher modulus of rupture and modulus of elasticity 

 than board with random placement of flakes, when loaded in bending in the 8- 

 foot direction in which the strands are aligned. 



By 1978, Canadian and one U.S. waferboard were approved by the Building 

 Officials' and Code Adminstrators' International (BOCA), the Southern Build- 

 ing Code Congress, and the International Conference of Building Officials. 

 These panels conformed to type and grade 2B2 of Commercial Standard CS- 

 236-66 (U.S. Department of Commerce, National Bureau of Standards 1966) 

 which called for minimum average modulus of rupture of 2,500 psi and modulus 

 of elasticity of 450,000 psi. They were approved for roof sheathing 3/8-inch 

 thick secured to rafters spaced 16 inches center- to-center, or 7/16-inch thick on 

 rafters with 24-inch spacing. For wall sheathing, approval came for 5/16-inch- 

 thick panels secured to studs 16 inches on center, and for 3/8- or 7/16-inch 

 panels on studs without comer bracing and spaced 24 inches center-to-center. 



AMERICAN NATIONAL STANDARD FOR PROPERTIES 



In 1980, the National Particleboard Association (1980) published an Ameri- 

 can National Standard For Mat-Formed Wood Particleboard. Type 2 particle- 

 board — that bonded with phenol-formaldehyde resin or equivalent — made of 

 wafers or flakes was required to have the properties shown in table 24-2. 



PERFORMANCE STANDARDS FOR COMBINATION SUBFLOOR 

 AND UNDERLAYMENT2 



O'Halloran (1979) noted that a performance-based specification is an alter- 

 nate to the more common commodity or product standard approach just de- 

 scribed. Performance specifications are product approval documents, qualifying 

 structural-use panel products emerging from new technology. 



Specifications include criteria reflecting durability, structural performance, 

 and dimensional stability when wet. Durability is based upon a cyclic wet-dry 

 test reflecting a minimum satisfactory performance equal to a minimum 1 -year's 

 exposure to weathering conditions. Structural adequacy is demonstrated by 

 concentrated static and impact tests in both a wet and dry condition. Finally, 

 dimensional stability is based upon field and laboratory tests of a variety of panel 

 products. Criteria for each of these areas are established from the laboratory and 

 field work. 



Text under this heading is condensed from American Plywood Association (1980). 



