The Wolowitz House is where Howard Wolowitz was living with his mother and father until something happened to all 3 members: Mr. Wolowitz left his wife and son when Howard was 11 before the Pilot. Howard now lives a miserable life with his mother, as their relationship strains sometimes.
In "The Killer Robot Instability", Howard became a hermit and refused to leave his bedroom for two days after Penny gave a meaningful call-out to him. Penny arrives after Leonard reminded her about what happened to Leonard after his visit with Kurt, Penny apologizes to Howard, forgiving him and bring him back to his senses.
Howard got married to Bernadette and he moved into her apartment in "The Habitation Configuration" and Mrs. Wolowitz passed away in "The Comic Book Store Regeneration" while visiting Howard's Aunt Gladys in Florida. Howard mentioned in "The Dead Hooker Juxtaposition" that his house is located in Altadena, California.
After Mrs. Wolowitz's death, Howard moved back into the house after he and Bernadette had moved out of their apartment and moved into the house which they decided to live in and are currently talking about renovating in "The Spock Resonance". Bernadette talks about how she thinks the "Jewish mother kisch theme" is depressing and she wants to change it. The rennovation has since been finished, giving a more modern theme.
In "The Fortification Implementation", a young man came to the house, Howard's half-brother Josh with whom he shares a father. Howard at first wanted him to leave when he couldn't stand the fact that his father has another family, but then they bonded over Howard being an astronaut and their similar personalities.