A ridge beam is a structural horizontal member positioned at the apex or highest point of a sloped roof, designed to directly support the upper ends of the roof rafters and transfer the roof loads (including dead load, live load, snow, and wind) to supporting elements such as posts, columns, or bearing walls.
Unlike a ridge board, which primarily serves as a non-load-bearing nailing surface and alignment guide for rafters, a ridge beam actively bears and distributes significant weight, making it an essential component in roofs where rafter thrust cannot be resisted by ceiling joists or other horizontal ties, such as in vaulted or cathedral ceilings, or roofs with low slopes.
For inspections, it is important to distinguish between a “ridge beam” and a “ridge board,” which are often confused in construction. The term’s common usage in the industry strictly refers to its load-bearing capacity. In conventional framed roofs with ceiling joists that act as rafter ties, the opposing rafters “push” against each other at the ridge, and the ceiling joists resist the outward thrust, making a non-structural ridge board sufficient.
However, in scenarios like vaulted ceilings where ceiling joists are absent, or for roofs with pitches below a certain threshold (typically 3:12 or 4:12, depending on local codes), the rafters cannot effectively resist thrust on their own. In these cases, a ridge beam is required to provide direct vertical support, preventing the roof from sagging and the exterior walls from spreading. This definition emphasizes its role in transferring loads, distinguishing it from merely being an alignment aid. Variations in meaning primarily occur between its structural function (beam) and non-structural (board), which this definition explicitly addresses.
Common materials used for ridge beams include engineered lumber types such as LVL (Laminated Veneer Lumber), glulam (glued laminated timber), and PSL (Parallel Strand Lumber), as well as structural steel. The size of a ridge beam is usually determined by a structural engineer based on specific load calculations. Recommendations should be tailored to the particular design conditions.
Example Usage: “During the framing of the new custom home, the architect specified a large glulam ridge beam to accommodate the vaulted ceilings in the great room, ensuring proper support for the long-span roof rafters.”