How to handle ongoing refactoring?

[j-bore]

Usually any seasoned project has some ongoing refactorings. Tasks that are too big or expensive to complete at once. So, team agrees upon the new direction and writes any new code according to that plan. And when they need modify existing features, they update them too.

This leads to inconsistencies in codebase. Especially in small teams they are not well documented but live as silent knowledge among devs.

What are your suggestions to handle this? I think, the most obvious place would be the constitution. You could describe the problem and the reasoning to change and maybe point out old "bad way" and new "good way".

How have you handled this?