Open-beam roofing techniques transform structural framing into an interesting focal point and enlarge your interior space with a view that stretches to the roof. Common design options for open-beam roofs not only change your home's appearance but also affect the roof's labor and materials requirements. An understanding of roof framing and vaulted ceiling construction helps you choose a design that suits your budget and building skills.
Load-Bearing Ridge Beam
Placing a structural load-bearing beam at your roof's ridge allows you to run beams unsupported between the roof's peak and adjacent load-bearing walls. The large, exposed beam of traditional adobe structures or modern southwestern architecture is a recognizable example of this design. In some cases, builders substitute a load-bearing stud wall for the the structural beam. Note that beams require posts for support. Depending on the beam's dimensions and allowable span, your project might only require posts at the beams ends or it might need posts throughout the structure.
Architects and engineers often specify custom metal plates and brackets to support open-beam roof designs. Plates and brackets often install on top of the structure's load-bearing stud walls. Alternatively, metal reinforcement might appear in the form of steel plates sandwiched between rafters, called flitch plate beams or flitch plate rafters. Metal cables are another common solution to open-beams designs. You can brace your rafters against thrust by connecting opposite rafters with taut steel cables. Although the cables run directly through the ceiling space, their appearance is discreet compared to conventional joists or collar ties.
The term collar ties refers to framing lumber that runs horizontally between opposite rafters, usually near the roof's ridge. These beams brace the rafters from thrusting loads and prevent the roof from sagging at its ridge or caving in. While collar ties do interfere with the open-ceiling view near the roof's ridge, they leave the majority of the roof framing exposed. Collar ties also provide a convenient installation surface for light fixtures and ceiling fans.
Open-Truss or Joist Design
Conventional wood-frame structures have beams running from wall to wall, called joists. Joists are often part of a prefabricated roofing unit, called a truss. Whether part of a joist or truss, the beams are relatively low, running directly across a room's ceiling. In normal circumstances, these beams form the installation surface for ceiling coverings, such as drywall. However, designers occasionally leave joist and truss beams exposed. The result is a partially open ceiling; the web of beams and rafters blocks roof framing from some perspectives and allows an open view from other.
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