Cowgirl95

I've done this side quest and started by bringing provisions to the Foreman at the timber co. Would then bump into the father and his sons and watch the house grow. Then I defended them from the O'Driscoll's and he gives you a reward. Then when you bump into him and get the timber, if you go back later in the game ( like a few days and nights for me) the house is more complete. However, if you do not save them or get them timber,the house never become fully finished. I also imagine that providing supplies to the lumber camp is important in this aswell as the foreman mentions that work will halt without provisions. I think it is one of those missions where you have to be patient and watch the characters to see the story detail. Hope this helps :)