If we were going to assign a gender to the two houses in this novel (and we are), we'd call the big house on the corner a girl house and the country home at Tres Marías a boy house.
OK, maybe that's a bit simplistic. But it does seem that, throughout most of the novel, space is divided into masculine and feminine realms. For the most part, Esteban Trueba dominates the country house and the front section of the big house on the corner, while his wife rules the roost in the back rooms of the house. Let's take a look at how those areas are described, and what that says about masculinity and femininity in the novel.
Certain traits – like forcefulness, physical activity, initiative, and a valorization of European and North American culture over Latin American – are associated with the areas dominated by Esteban Trueba, the book's masculine powerhouse. Esteban fixes up the house at Tres Marías with his bare hands and a stack of instructional manuals, employing his tenant farmers as laborers and commanding them with an iron will. He furnishes the place with "large, heavy, ostentatious pieces that were built to last for generations and to withstand country life," and arranges them "along the walls, with an eye more to convenience than aesthetics" (2.54). Creativity and inspiration have no place here – when the house is destroyed in the earthquake, Esteban has it rebuilt in exactly the same way. Nor does Clara's supernatural nature seem to affect the house at Tres Marías – she's always too busy with the practical matters of improving the quality of life of the tenants to engage in any spiritual activities.
When it's first built, the big house on the corner has Esteban written all over it, too. It's "solemn, cubic, dense" and "pompous," built to last for generations, and can house lots of little Truebas. Esteban designs it in a European style because he wants it "as far removed as possible from the native architecture." He wants the house to reflect his wealth and prestige, as well as the order and civilization that are, in his opinion, "typical of foreign peoples" (3.63). The house is all heaviness and straight lines, with snobby, imported furniture.
But then Clara moves in, and her feminine presence acts as a catalyst for change. Though the big house retains its Colonial-style façade, Clara slowly begins to work her magic on its insides, until the place begins to reflect her qualities of spirituality, inspiration, creativity, and complexity. Soon the rear part of the house is full of "protuberances and incrustations, of twisted staircases that led to empty spaces, of turrets, of small windows that could not be opened, doors hanging in midair, crooked hallways, and portholes that linked the living quarters so that people could communicate during the siesta." These changes are made according to Clara's inspiration and the instructions she receives from the spiritual world. And while they may sound chaotic, they create a world of peace and "complete freedom" for the female characters in the novel (9.45). It's also significant that the mansion "[defies] any number of state and city laws," because it reminds us of the way in which Clara's feminine magic challenges patriarchal authority (3.64).
Clara is the "motor that [drives] the magic universe" of the big house, and when she dies, the spiritual energy and constant flux of its architectural design come to an end (9.45). Without Clara's feminine presence to counteract Esteban Trueba's violent, masculine energy, no one bothers to fix the cracks in the walls or the broken furniture. The house becomes a ruin.
But don't worry – just because Clara is dead doesn't mean that this story has to end like a bad middle school dance, with boys on one side of the room and girls on the other. Clara sticks around as a ghost, and she and her husband make peace. Their reconciliation is reflected in the house's appearance – the invisible border that had been drawn between Esteban's territory in the front of the house and Clara's rear rooms dissolves, and the house is restored to its former glory. Esteban and his granddaughter Alba walk the entire house, paying tribute to the spirits, and put the rug made out of Barrabás (Esteban's idea of a wedding present) back in Clara's bedroom.