I have a 5 year old, 3 story building with 20 inch logs. Some of the lower logs on the south side are showing some significat checking, as wide as 4 or 5 feet. There appears to be some rot inside. I want to treat the wood and chink. Should I do anything about the rot first and what type of products are best for that , for the treatment and for the chinking? I would appreciate any advice, especially having to do with the rot.