In 1977, when the Log Homes Council (now the Log & Timber Homes Council, or LTHC) formed, the 22 charter members identified grading as one of the biggest challenges facing the log home industry, driven largely by building officials who insisted that the code requirement for lumber grading be applied to logs — not exactly an apples-to-apples comparison.
To resolve the issue, the LTHC enlisted the help of a team of wood scientists and other experts; and in 1980, it established its pioneering visual-grading program. In 1994, Timber Products Inspection (TPI) followed suit with a log grading program of its own.
Today, the LTHC’s log grading program is accredited and referred to as the ICC400-2017 “Standard on the Design & Construction of Log Structures,” mandating that all structural logs be graded by a recognized agency.
What is Log Grading?
“It’s the visual inspection of all surfaces of a log by trained and certified personnel,” explains Rob Pickett, who is not only a certified log grader, he also helped establish the LTHC’s program.
Log producers employ staff who are trained to inspect and certify the logs in-house. To ensure their accuracy, periodic spot checks are conducted by qualified third-party field agents.
“The process begins by immediately rejecting those sections of a log that contain evidence of decay, insect attack or other forms of weakness,” says Rob. “The next step is to examine each piece to determine its strength — greatest when the grain is straight and clear of knots.”
In the LTHC’s program, log grades are documented as “beam,” “header,” “wall” and “utility,” strongest to weakest; whereas TPI uses the names “premium,” “select,” “rustic” and “wall.” Though the two programs use different naming conventions and have slightly different grading criteria, for structural purposes, they are essentially equal.
The Importance of Log Grading
By certifying the grade of a log, structurally unsound timbers are eliminated long before they are installed. It is equally important to identify logs that are structurally superior and can span as headers or beams — load-bearing conditions that require a better or stronger grade to be used.
“By purchasing a graded log package, the buyer is assured that higher-grade logs are marked to indicate that they should be used for headers (i.e., logs spanning over window or door openings) or other structural conditions,” Rob says.
How Do I Know if it’s Graded?Buyers and builders can tell if a log has been graded through a combination of marks made on the log, itself, as well as a written Certificate of Inspection (COI) that accompanies the log package during shipment and is given to the customer upon delivery. This COI also serves as the principal document explaining the grading system, number of pieces and other relevant information.
The plans will show the building inspector that the minimum log grade in all structural applications has been met or exceeded, giving you peace of mind that your log home will stand strong.