Do I really need to wait until the logs are dry to chink?

This month’s training tip comes directly from a question we received recently. A customer asked, “Do I really need to wait until the logs are dry to chink?” Our very own Jim Barnes, Senior Stains Chemist, answers this question.

Chinking Training 2

A customer recently shared with us that they’ve had two different log contractors (the one who built the home and one a general contractor recommended) tell them that they would chink over the logs even though they had 30%+ moisture content. The customer expressed that, “The big thing is that there's so much conflicting information between what we've been told versus what I've learned from my research that we've lost valuable time trying to make sense of what to do first. We're busy trying to mitigate the damage as a result.”

Avoid this situation yourself! Here is the proper information YOU need.

Answer:

To stain and chink, the wood needs to be dried to the equilibrium moisture content (EMC) for that location. This is a link to some average EMC for a variety of areas,

https://research.cnr.ncsu.edu/blogs/wpe/files/2016/08/Equilibrium-Moisture-Content-of-Exterior-Wood-in-the-US.pdf

There are two important reasons for waiting for the wood to be dry before staining and chinking.

  1. Stain and chinking won't adhere to wood as well when it has a high moisture content.
  2. As logs dry out, they shrink and move/warp/shift, and that places a LOT of stress on everything put on top: the stain, sealants, and chinking. You risk massive peeling and cracking. 

Imagine that green or wet logs are touching (zero gap) at a 30% moisture content when a 1" chink joint is applied. At 18% moisture content (winter), there may be enough shrinkage to open a 1/2" gap between the logs in places and at 10% moisture content (summer) it might be a 3/4" gap. So, we are asking a 1" chink joint to be stretched to 1 1/2" to 1 3/4" and always be stretched under tension. Under these conditions, we expect the chink joint to fail and split or lose adhesion at one side.

Now, imagine that the logs are at the 14% average EMC (with a small gap between logs) and a 1" chink joint is applied. As the wood cycles between 10% and 18% EMC over the years the movement is a range of 1/4", or 1/8" of expansion in one season to 1/8" of compression in the other. We expect the chinking to perform extremely well under those conditions. (Your logs may need a different size chink joint - typically 15% of the log diameter, and they may shrink/move more or less than these numbers. These numbers were only used as an easy example.)

Pro Tip: Ideally we prefer chinking and caulking to split, rather than lose adhesion, because splits are easy to fix by. because it is easy to fix by applying more chinking. That's why we recommend round backer rod, the round shape places the weakness (thinnest spot) in the middle of the joint. When chinking loses adhesion at the edges, fixing it means tearing out that whole section, cleaning the sides of the joint and re-chinking. Still doable, but a lot more work.

At the end of the day, doing much of anything on wet logs is a big risk. Just wait. In the meantime, try to get them dry.

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