An egress window must meet specific standards in the state of California. They must have a minimum net opening of at least 5.7 square feet.Residential buildings can't have windows that open more than 4" so no one accidentally falls out. In this article, we will discuss what construction and remodeling work can and cannot be legally completed without a building permit. The egress window should have a minimum net opening area of 5.7 square feet. Anyone here ever design windows into an existing masonry party wall? Or is that just a bad idea in general?