Do I really need to wait until my logs are dry to chink? | Here to help!


A customer recently emailed in with this question and had already received conflicting information. The short answers is YES, but we don't do short answers very well here at Sashco, so we shared all kinds of details on why waiting is best and sent these folks away with more information than they expected. Keep scrolling to read all of these details.
This customer shared that they had two different contractors tell them that they would chink over their logs even though they had more than 30% moisture content. The customer expressed, “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. 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.”
 
While we already gave you the short answers above (yes, please wait), we invite you to geek out over the details of why for just a moment. These details are courtesy of Jim Barnes, one of Sashco’s Senior Chemists.
 
To stain and chink, the wood needs to be dried to the equilibrium moisture content (EMC) for that location. Click here for a link to some average EMC for a variety of areas.
 
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 the product applied on that wood. It especially puts sealants and chinking at risk of failure.
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, at least in some places. At 10% moisture content in the 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 — it will either 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.)
 
So, the short answer is wait until you’ve reached that EMC. If you must seal before then, be prepared for repairs until that EMC is met.
 
Pro Tip: Ideally, we prefer the split because it is easy to fix. That's also why it’s always best to also use round backer rod behind the chinking or sealant. 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.