Crown moulding is an affordable way to upgrade any room in your home by adding a feeling of warmth and elegance. Without crown moulding, even the most beautifully decorated rooms look unfinished. By definition, crown moulding runs along the top of a wall where it meets the ceiling. The wider the moulding, the more stately the effect. Because ceilings and walls are rarely perfectly square, crown moulding can be tricky to install. That’s why most “do-it-yourself” homeowners will hire a professional when it comes to installing crown.