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Ridge board vs ridge beam: what it means on an inspection

Rafter Tie editorial teamUpdated 4 min read

A ridge board is a board at the peak that gives the rafters a place to nail; the rafters lean on each other and need ties. A ridge beam is a structural member that carries the rafters, so it must be held up by posts or walls. The first aligns the roof, and the second supports it.

Two roof cross-sections: on the left a thin ridge board between rafters that lean on each other, with a low tie; on the right a deeper ridge beam held up by a post under the rafters
Board: rafters carry each other. Beam: the beam carries the rafters.
Use this diagram

How to tell a ridge board from a ridge beam

  1. Look at what holds the peak up. Under a ridge board there is nothing: the rafters hold each other up and the board just lines them up. Under a ridge beam there are posts, columns or bearing walls at its ends and often at points along it.
  2. Check the depth. A ridge board is generally as deep as the cut ends of the rafters, so it gives full contact for nailing. A ridge beam is sized for load and is often much deeper than the rafters, so the rafters sit on it or hang from it at its sides.
  3. Ask where the thrust goes. With a board, the rafters push the walls outward and ties or ceiling joists must hold them. With a beam the ridge is held up from below, so the rafters do not push the walls outward the way a leaning pair does.
  4. Find the size source. A ridge board is sized as a board. A ridge beam needs a size from a span table or an engineer, because it carries a share of the roof load.
  5. Trace the load down. For a ridge beam, follow the posts to something that can carry them: a foundation, a footing or a beam below. A post that stops on a floor with nothing under it is a finding.

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In a new bedroom, the only emergency escape window has a keyed sash lock, with the key hanging on a hook beside the window. What should the inspector do?

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Common mix-ups

  • A bigger ridge board is not a beam. Making the board thicker does not give it the support at its ends that a beam needs.
  • A ridge beam does not remove every tie question. Some conditions, such as dormers or changes in framing, still need connections. Read the rules for the roof you have.
  • Cathedral ceilings and ridge beams go together. Open ceilings leave no ceiling joists to act as ties, so many designs use a ridge beam. A ridge board in an open ceiling needs another way to resist thrust.
  • Ridge versus hip and valley. Hips and valleys are roof lines where two planes meet. They have their own framing rules and are not interchangeable with the ridge.

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Ridge framing on the B1

The B1 outline puts roof and ceiling framing at 14%, and ridge members are a classic way to test load path. Expect a short description of a roof and a request to decide what member or connection is missing. Chapter 8 holds the roof framing rules; find them by name and confirm the section numbers in the edition you will bring.

Practice it

Pick a roof with a 12-foot run and use the rafter length calculator to see how pitch changes length, then read roof pitch for the rise-over-run language. After that, review rafter ties versus ceiling joists, which explains what holds a board-and-rafter roof together, and return to the glossary for the next term.

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