What To Do Once The Original Problem Is Addressed:
Once the source of water has been eliminated, remove as much decayed wood as it is necessary, Even when its shows to be unpractical and not economical, because you will pay a bigger price later if you don’t.
Don’t try to convince the workman to close it back up. It is unethical and plain wrong. These problems need to be addressed for the sake of safety and lives may depend on it. Sell the house to someone who has the money to fix it, but don’t try to hide the problem.
This is especially important with girders, columns, and other critical members whose load-carrying ability may have been compromised. There’s no known way of accurately determining the remaining strength of decayed wood left in place. Sometimes a wood damage requires re-engineering of the entire structure.
Cut back rotted members to sound wood, keeping in mind that difficult-to-detect incipient decay can extend well beyond visibly rotted areas. We call this kind of work exploratory work, where we charge on a time and materials basis.
When a partially decayed structural member can’t be replaced, reinforce it with a “sister” anchored to sound wood. Decayed wood absorbs and holds water more readily than sound wood, so let rotted areas of members not removed dry out before making repairs and closing in. Otherwise, you’re just adding fuel to the slow fire.