There is probably only one building in the entire world known solely for its ceiling: the Sistine Chapel. When people enter the Sistine Chapel, they immediately look up. Few even notice the rest of the architecture.

The ceilings remodelers make probably will not approach the beauty of the Sistine Chapel, but that doesn't mean flat, drab ceilings have to be the norm. A coffered ceiling, for example, can give a room the extra design oomph it needs. And it's relatively simple to do.

No matter what kind of ceiling you build, though, it has to work structurally. It must provide shelter and keep heat and moisture from penetrating the attic space. Providing shelter is more a function of the roof than the ceiling. But controlling heat and moisture penetration is largely the ceiling's job.

Pretty Coffer

There are three different types of coffered ceilings: intersecting beams, barrel-vaulted and tray. The intersecting beams type is the easiest to add to an existing ceiling. The simplest method for building intersecting beams is to nail 2-by material flat to the ceiling in the pattern you want. You will need to add blocking for beams running parallel to the ceilings joists. Usually, intersecting beams are done in larger rooms, which allow you to make bigger squares. Trim out the blocks with 1-by material. Leave a reveal on the bottom piece of 1-by to give the beam more definition. You also can use bed molding or crown molding to cover the joint between beam and ceiling.

Barrel-vaulted ceilings are more difficult to construct. You cannot add a barrel vault to an existing room unless the ceiling is taller than usual. Make the barrel-vault out of pieces of plywood, cut in the arc you need. Use blocking between two pieces of plywood to create a box beam. You'll attach the drywall or beaded board to this framing.

The third type of ceiling is the tray ceiling, and you can install it in existing rooms. All you have to do is frame a soffit around the room, with the vertical edge sloped towards the center of the room. Of course, if the room has only an 8-foot ceiling, adding a soffit will not leave you much headroom. In fact, in most localities this would be a code violation. A 9-foot ceiling works much better.

With new construction, frame the tray ceiling on top of the walls. (See Figure 1.) The corners have to be absolutely square or the ceiling will look lopsided, so check the diagonal before you begin framing. Run double joists down the length of the room, stopping them short of the parallel wall to leave just enough space for the soffit. Then, run double joists in the same way across the width of the room. Fill in the soffit with lookouts at 16 inches on center.

To frame the center, raised portion, lay it out like a hip roof. Instead of a ridge beam, though, you build a box. Lift the box into place and brace it. Then cut and install the rafters. The ceiling joists get framed in the usual way.

Tightening Up

A pretty ceiling doesn't work if moisture and heat can penetrate it to cause problems in the attic. Since heat rises and warm air carries more moisture than cool air, all the hot air at the top of the ceiling is just begging to start mold and mildew problems.

You rarely see mold and mildew problems on the inside of the room, where air is allowed to circulate. But in the attic, where ventilation can be inadequate, it's a different story. Keeping ceiling penetrations to a minimum can reduce heating costs significantly, too.

To avoid these problems, start with interior walls. An alternative to the normal framing method for interior walls is to frame them after the ceiling is drywalled. This allows you to create an airtight drywall barrier.

Of course, installing the drywall first can create problems. For starters, the 2 x 4 studs used for framing the walls will be too long. There are a couple of solutions. You can cut that extra half-inch off of each stud, but that's time-consuming and expensive. You also would need to cut them a little more than that so you can tip interior walls into place. Then you would have to shim the walls.

A better solution is to lay a piece of 1-by material on the top plate of the exterior walls before you set your trusses. (See Figure 2.) That will raise the ceiling joists enough to allow for the drywall-up to 5/8-inch stock-and still provide room for tipping the walls into place.

Besides walls, plumbing stacks and electrical wiring also penetrate the ceiling. Seal the plumbing stack by running it through a rubber membrane such as EPDM roofing material. (See Figure 3.) Wrap the bottom of the plate with weatherstripping. Then cut the EPDM into a square. Slice an X in the middle large enough to slide the stack through and tack the whole thing in place.

Electrical penetrations are much easier to finesse. You can purchase electrical box gaskets that will do the job quickly. For recessed lights, use only fixtures designed to be in contact with insulation, ensuring a tight seal. Ductwork, too, should be sealed to the drywall to prevent air leakage.

Another big hole in the ceiling is the attic access itself. The top of the hatch needs to be insulated, preferably with rigid foam insulation cut to the same dimensions as the hatch. Glue it right to the hatch. On the ledger boards holding the hatch, place weatherstripping. Hold the weatherstripping off the edges enough so that it can't be seen from below. Don't seal the hatch with caulk. A service worker may need to get up there someday.

None of these measures will do much good, though, if the drywall itself isn't sealed up tight. You can place gaskets all around the drywall to prevent leakage, called the airtight drywall approach. Or you can cover the framing with plastic before you install the drywall.

Ceilings often are overlooked, regardless of their quality of construction. Except for the Sistine Chapel, of course.