In "the revolt of 'mother,'" the subtext regarding the conflict over the new barn is that the barn represents

a new start on the house that sarah wants
a way for sarah to rebel against her husband
a change in the relationship between husbands and wives
a victory for sarah over adoniram

The best answer would be 

a change in the relationship between husbands and wives

Because Sarah defied the relationship of a typical family by rebelling against her husband, and she had found self-assertion in her self that would prove to empower her. She had done everything just to improve the life of her family. 

Look at the passages where the author describes the isolation and insanity that dr frankenstein has