Finish Carpentry: Wood Trim
This information can clarify and help answer some questions about wood trim.
Moldings: Moldings (or "trim work") are both functional and decorative. Although they give a room distinctive style and detailing, they also serve a purpose: to hide the joints between walls and floors, ceilings, doors, and windows. Many patterns and styles are made from a variety of both softwoods and hardwoods. These profiles can be used individually or in combination-called built up moldings-to create intricate patterns.
Moldings in older homes may be made of plaster, particularly cornice and crown moldings, or any of the several hardwoods or softwoods. New moldings are sold at lumberyards and millwork shops, the best places to see the wide selection available.
Hardwood moldings that are meant to be stained or finished naturally are relatively expensive; much less expensive are paint-grade pine or fir moldings made from short pieces that are finger joined together. A range of ready-to-paint, decorative moldings made from high-density polymers are also available.
Polyurethane moldings don't expand and contract, warp, decay or require heavy maintenance. And because intricate polyurethane moldings are made as single-piece units, they're also much cheaper to install.
Window/door casings are not only used to hide where the jam meets the wall surface, but they also serve a practical function by keeping wind and weather out of the house.
Some carpentry terms: A fascia is the edge of a roof or the part of a house where to which a rain gutter is attached. A soffit is a dropped, boxed area of a ceiling or roof used to cover pipes and wiring that may run along a wall. The soffit connects to the fascia.
-- Tips courtesy of HomeAdvisor.com