Ridge Board and Ridge Beam

The ridge is the highest horizontal line of a pitched roof, where two slopes meet. In framing, the timber running along that line goes by several names, and the distinction between a ridge board and a ridge beam matters structurally.

Ridge board

A ridge board (in Britain often called a ridge piece or ridge plate) is a relatively light board set on edge at the apex. Opposing rafters are nailed against it, which makes the roof easier to assemble and keeps rafters aligned. A ridge board does not hold the rafters up on its own. The roof stays stable because something else stops the rafters from spreading, usually ceiling joists, rafter ties or a tie beam at the bottom, which together with the rafters form a triangle.

Ridge beam

A ridge beam is a structural member, sized by calculation, that carries the upper ends of the rafters and is itself supported by posts or walls at its ends and sometimes at intermediate points. It is used where there are no ties across the bottom of the rafters, for example with vaulted or cathedral ceilings. Because the beam supports the rafters vertically, they do not push the walls outward in the same way.

Historic framing

In medieval and later timber roofs, the king post was traditionally the vertical timber that rose from the tie beam to carry the ridge. Many old roofs had no ridge member at all, with rafter pairs simply joined at the apex.

Weatherproofing at the ridge

The structural ridge is covered on the outside by ridge capping: ridge tiles bedded or mechanically fixed in tile and slate roofs, ridge cap shingles on asphalt roofs, or a formed metal ridge cap on metal roofs. Ridges are also a common location for exhaust ventilation.