What is Resistograph Testing?

Resistograph testing on an old wooden pier.When looking at a timber structure, the exterior can sometimes tell a different story than the interior. Determining the condition throughout the entirety of a wood member is critical in confirming that the structure can safely continue to perform its intended purpose. Coffman’s Portland office has used resistograph testing to provide our clients with the necessary information to understand the current quality of their timber structures.

Resistograph testing utilizes a resistograph tool that drills through an existing wood member with a small diameter drill bit and records data throughout the drill. The machine outputs a density graph relative to itself that shows the solidity of the wood member, displaying possible voids or areas of low density, which could be due to rotting. This testing can provide data that supports an extended life for wooden structures, along with visual observations to help determine if replacement is needed to maintain the structure’s longevity.

Resistograph Applications

Coffman has performed resistograph inspections on docks, utility poles, and observation platforms for local, state, and Federal clients. This technology is useful for any existing timber structures and can be applied to projects involving structural wood such as residential, industrial, utility, and bridges; and tree inspections to maintain the safety of areas near parks, roadways, or other heavily populated areas.

Coffman has successfully gathered and interpreted data through our resistograph testing, allowing our clients to make informed decisions for their structures. We have had projects where the testing data concluded that only partial replacement of the wood members was required. Results like these have surprised clients by showing that the wood within their structure did not lose structural integrity and did not require the anticipated replacement, saving the client money. Resistograph testing is a valuable tool that provides the data necessary to evaluate aging wood structures.

Using Resistograph Data in Practical Applications

One example project where Coffman utilized resistograph testing was at Commonwealth Lake Dock in Hillsboro, Oregon. The Tualatin Parks and Recreation Department requested we perform testing on the existing dock because there was some visual checking and possible rotting of the timber piles. We went on-site and drilled into each structural pile and the framing beams to analyze if any rot was present. We were able to map out which specific structural members needed replacing due to the amount of damage and rot presented through our test graphs.

Resistograph testing on an old wooden pier.Resistograph Testing & Interpretation Services

When considering an upgrade or replacement for wood structures, Coffman can help you make informed decisions regarding the lifespan of a current structural timber member. Resistograph testing is a quick way to confirm the structural integrity of timber members where visual inspections may fall short, which could lead to avoiding unnecessary replacement costs.

Contact Coffman’s structural engineering team to learn more about our resistograph testing capabilities and how we may help develop solutions for your next project.

For more information, contact Steve Hawk, PE.