I have a square log building built in 2005. One log now has rot on the upper side. It is the bottom log. I discovered it when I was power washing and noticed a fungus growing out from the joint. I have now reamed out the area (about 5 feet long, 2-4 inches deep and 2 inches wide) and have a nice day to get the area dry. What do I fill this long strip of log with and how?