Lumber grading rules are a set of criteria used to determine how various characteristics, such as wane or knots, affect the structural performance of dimension lumber or the aesthetic value of Appearance Grades. Lumber manufacturers are responsible for grading the lumber to these rules and RIS, as part of the American Lumber Standards system, helps assure that Redwood lumber meet stated product quality standards.
The Redwood Inspection Service (RIS) is exclusively authorized by the American Lumber Standard Committee to formulate grading rules for redwood lumber established in accordance with Product Standard 20-94, the American Softwood Standard, issued by the U.S. Department of Commerce.
RIS, a division of the California Redwood Association (CRA), publishes and maintains the Standard Specifications for California Redwood Lumber Grades.
BUYER BEWARE WARNING: The pattern measurements below are CRA industry standards. HOWEVER individual mills often have their own pattern standards which vary from the norm (usually smaller). When you get ready to buy be sure to ASK for the exposed width to make sure you are buying enough SQFT of Redwood Siding to complete the job!
