Opening up the ceiling.

Just above your head in most gable-roofed houses, there's an overlooked space with rich potential for remodeling: the triangular void called the attic.

Removing the ceiling and reclaiming some or all of the attic volume can make a startling change in a room's appearance--at a relatively low cost, compared with changes that expand floor space. Without altering the width, length, or outside roof shape of this part of the house, you make the room seem bigger and brighter. Angular end-wall shapes and soaring volumes add visual drama, too.

All in all, when your room for expansion is limited or budget constraints must be considered, an opened-up ceiling can give you a lot of esthetic value for the dollar. But interrupting the geometry and the structural integrity of a roof isn't something you can do without thoughtful planning.

On these pages, we show 10 different ways that homeowners have opened up the ceiling and pushed into the attic. Their approaches run from an almost-instant remodel, in which a gypsum-board ceiling was merely removed, to complex engineered projects that carefully redistribute roof loads. How a roof works

If you think of an isoceles triangle that is propped up at both ends of its base, you'll picture a cross-section of a typical gable-roofed house. The end supports are the bearing walls that carry the vertical load of the roof to the foundation. The horizontal ceiling joists tie the sloping rafters together, creating a rigid triangular shape. The weight from the slope pushes down and out on the walls. It's the joists that lock everything together and keep the walls vertical. Breaking the geometry

If you remove joists, the roof structure will be weakened unless you do something to maintain the integrity of the triangle or redistribute the roof's load. The examples on these pages show a variety of solutions: removing some joists and doubling up others, tying the roof rafters together with collar ties (cross-pieces that parallel the old ceiling level but connect at points higher up the rafters), or taking some of the roof load off the walls and carrying it with beams added at the ridge or at points along the rafters.

Unless ceiling joists are oversize, they seldom span the entire width of a house. Usually, they are composed of two lengths of lumber (2-by-4s or 2-by-6s) that connect in the middle and rest on a central load-bearing partition. In examples where this central bearing wall was extended to the ridge line, only half the attic is exposed, and the central wall carries more of the roof load.

In newer tract homes, builders often use ready-made roof trusses that span the house from side to side with no central bearing wall. Interrupting these would almost certainly require a more complex engineering solution.

When ceiling joists are removed, one common way to help make up for the loss in strength is to nail plywood to end walls or interior bearing walls; this helps distribute weight loads and adds shear strength (against sideways stresses). Energy, insulation, and other concerns

There are a few trade-offs when you raise the ceiling. For one thing, the increased volume of living space is bound to require more energy to heat and cool. In addition, ceilings can mask a morass of pipes, wires, vent lines, heating ducts, and insulation.

Most of the heating ducts and the plumbing and electrical lines can usually be rerouted, but insulation remains a concern: where does it go?

If the existing rafters are deep enough, you can staple in batts of 6-inch fiberglass insulation to get an R-19 ceiling. For shallower rafters, you could insert rigid foam insulation (2-inch-thick foam is rated at about R-14). To gain additional depth, nail furring strips to the bottom edge of each rafter, then add insulation.

Structural engineers feel that for older houses, which often have only 2-by-4 rafters, a more drastic step might be necessary both for insulation and for structural strength. They recommend removing the roofing material and covering the existing sheathing with plywood, which will strengthen the whole roofing system. Next would come a layer of rigid foam insulation, then a new layer of skip sheathing, and, finally, shingles.

With higher ceilings, heat recirculation can be another concern. Paddle fans or recirculating ducts can draw trapped heat from the top of the room and drive it down to floor level. Because the rafters are so accessible, it's easy to add skylights to these overhead spaces. Besides providing natural light, an openable skylight can help vent trapped heat in warm weather.

Unless you plan to remove only the gypsum board, opening up a ceiling is likely to involve structural changes that will require the advice of an architect or a structural engineer.