DIS-TRAN Steel Blog

Without knowing all the Rural Utilities Service (RUS) or American National Standards Institute (ANSI) specifications off the top of your head, it can be hard to decipher what is considered “on grade” relative to  wood distribution crossarms. However, here are a few general signs that can help you determine if “The Wood is Good”.

1. Size- review the section size of the arm. It’s a simple measurement; when you purchase a particular size, make sure it meets that measurement.

2. Tolerance- this is the allowable variation between the size specified and what may be supplied, which for both RUS and ANSI, can be plus one-eighth of an inch to minus zero.

3. Density- for close grain material, there should be a minimum of six growth rings per inch on at least one end. There are exceptions to the rules, such as having five rings, but it has to be with half or more summerwood present.

4. Drilling Pattern- this can either be one of the industry standards or specified by the end user. However, hole diameter and spacing must be correct, regardless of the standard.

5. Splits- are a separation of the wood from one face to the opposite or adjacent face and they are not allowed.

6. Seasoning Checks- “cracks” that can form when the wood is dried. If dried improperly, the check could go too deep; they are limited in length and width.

7. Shake- separation within the same grain; generally a cause for rejection but may be considered acceptable by some if more than one inch from the face. 

While the seven listed above are more visual signs, there are also more in-depth ways of knowing if the quality of the wood is good. Below I’ve listed out just a few terms that can come up when inspecting wood distribution crossarms under RUS specifications.

Pitch and bark pockets are concave areas on the surface formed from collecting pitch or bark trapped between growth rings. They are limited in number and size on the top of the crossarm as they hold water.

Insect and pin holes are from insects burrowing into the wood. No insect holes are allowed over 3/32” dia. and “scattered” pin holes are allowed less than or equal to 1/16”

Wane is an absence of wood on an edge or corner due to any reason but an eased edge and though allowed is limited in size

Compression wood is abnormal and often brittle wood formed on underside of bent or leaning trees; is not allowed on any face

3 Forms of Warp:

1. Crook is permanent bending of the lumber edgewise; limited

2. Bow is permanent bending of the lumber flatwise; limited

3. Twist is a permanent spiraling of the lumber; limited

Heart and sap stain is discoloration due to exposure to the elements; heart stain is not allowed but medium stain sapwood is acceptable

Decay is disintegration of wood due to fungi and should not be present in the wood

Slope of grain is grains direction relative to the ends of the piece; limited based on section size

Heart center is when the piece of lumber includes the very center of the log; is not allowed for Douglas-Fir but is acceptable in Southern Yellow Pine

There are countless rules and requirements that we could go into, but it can get a little confusing. If you would like to know more, you can download our RUS Cheat Sheet for Wood Distribution Crossarms to find out more unique requirements.