Vaulted ceilings can be used to create a dramatic look in just about any room. The extra volume that a vaulted ceiling adds to a room creates a sense of openness that few other architectural features can match.

First things first: if you’re thinking about converting a room with a flat ceiling into a vaulted ceiling room, run (don’t walk) to your nearest residential structural engineer. Many local building codes require that a structural engineer sign off on any changes made to the roof of your house—and with good reason! An improperly constructed roof can warp, sag or even collapse. A structural engineer can create a roof design that takes into account the required roof loads and unique layout of your home.

The Anatomy Of Your Ceilings
The cross section of a typical residential roof is a triangle pointed at the sky. The triangle is made up of rafters on two sides and a joist along the bottom. It takes many of these triangles, spaced at regular intervals, to hold up your roof. The strength of your roof is directly tied to these triangles—if any leg of the triangle were missing, the structure would collapse.

Altering The Triangle
In a typical flat ceiling, drywall (or some other covering material) is attached to the bottom of the joist. In order to create a vaulted ceiling, the joist would have to be removed, but removing the joist would fatally weaken the roof.

The solution to this dilemma is to keep the triangular support, but to move the horizontal support upward. Consider the difference between a triangle, and the letter “A”. Both have two angled sections and a horizontal section. The “A”, however, has a raised horizontal section that creates extra space below it. There are a number of ways to achieve this raised horizontal support, including:

• Collar ties — Just like the cross bar of the “A”, collar ties use wooden horizontal members placed about two-thirds of the way up the height of the roof. These horizontal pieces are attached to existing rafters to create structural strength.
• Gusset plates — Triangular plates constructed of plywood, gusset plates can be installed at the peak where the two rafters meet. Gusset plates can be quite small and still provide a great deal of structural integrity.
• Metal stays — Using heavy gauge wire or metal rods, metal stays serve the same function as collar ties. Metal stays, however, take up less visual space and can give your vaulted ceiling a clean, modern look.

Once you’ve altered your “roof triangle”, you can finish your vaulted ceiling by creating a new drywall ceiling or by leaving the beams exposed and covering the underside of the roof with a decorative wood finish. Don't forget the lighting for your vaulting ceiling.