A ridge beam carries the loads of the rafters connected to it and must be both strong enough to carry the weight and well supported at the bearing points at each end, to transfer the loads down to the ground. While the joists commonly attach to the side of a ridge beam, they can also sit on top of it, as shown in the diagram below, which creates an interesting look when the roof structure is exposed as part of the design.


    Because a ridge beam often carries a significant area of roof load, they can exhibit structural distress due to a defect in wood, impact on the roof, or use of an undersize beam.  The ridge beam shown below, at the living room of a 1950s modern-style ranch house in Gainesville, has cracked at mid-span and is slowly heading towards failure after the crack opened further after a recent repair.


    One of the advantages of using a ridge beam instead of a ridge rafter is that the ridge beam carries the loads that would otherwise get transferred downward and then laterally to the end bearing walls, and exerts outward pressure at the top of the wall which, if not contained, will simultaneously cause the walls to splay and the ridge to drop lower.


    When a ridge board is used, there are several choices for containing the lateral pressure:
  1. 1)Ceiling rafters - Although their primary purpose is to provide a structure for supporting and attaching the ceiling, ceiling joists prevent the walls from the spreading apart by being connected to the rafters at each end of the span and creating a triangle. The ceiling joists are in “tension,” meaning that there are forces pulling on them from each end created by the roof loads.

  2. 2)Collar ties - These create the same necessary structural triangle, but do it a little higher up on the rafter. They do not have to be installed at each rafter pair, and add visual interest when the roof structure is open to the room below. To learn more about them, see our blog post “What is a collar tie?”

  3. 3)Tension rods - Steel rods between the ends of the joists or top of the wall at regular intervals, when exposed, also provide an elegant solution. Steel is extremely strong in tension, so the rods can be a small diameter.

    The photo below shows a home where the structural triangles were disrupted by retrofitting a small shed dormer into the attic. As you can the see, the ridge sagged at the center as a result and, when viewed from the side, the walls splay outward below the area.


    Manufactured roof trusses do not need a ridge rafter or ridge beam. They have triangulation built into them, so any additional structural members to resist the lateral loads are not necessary.

 
 

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More blogs posts about similar subjects:

  1. How do you determine when the house was built?

  2. If my roof is not leaking, why does it need to be replaced?

  3. Should I buy a house that needs a new roof?

  4. What are the warning signs of a dangerous deck?

  5. I’m buying a ‘50s modern house with a “gravel” roof. Is it going to be a problem?

  6. What’s my chance of buying a Gainesville home over a sinkhole?

  7. How much of a roof truss can I cut out to make a storage platform in the attic?

  8. How can I tell if cracks in the garage floor are a problem or not?

  9. There’s cracks running along the home’s concrete tie beam. What’s wrong?

  10. What can you tell me about buying a house with structural problems? It’s priced cheap!

  11. Should I buy a fixer-upper?

  12. What causes cracks in a driveway?

  13. How much can I cut out of a floor joist?

  14. We looked at the house carefully, and it seems alright. Do we really need a home inspection?

  15. Should a home inspection scare you?

  16. What should I look for when buying a “flipper” house?

  17. How can a tree damage my house?

  18. How do I remove cigarette odor in a house?

  19. The house has asbestos siding. What should I do?

  20. There’s an old fuel oil tank underground in the yard. Is it a problem?

  21. What are the most common problems with older houses?

  22. What do I need to know about buying a 1950s house?

  23. What are the warning signs of a dangerous attic pull-down ladder?

  24. Why are there score line grooves in the concrete floor of the garage?

  25. What are the common problems of different types of house foundations?

  26. What are the common problems to look for when buying a 1970’s house?

  27. What is a “continuous load path”?

  28. Is painted bathroom tile acceptable?

  29. Should I buy a house that has had foundation repair?

  30. What causes a lump or dip in the roof?

  31. What are the most common problems with wood roof trusses?

  32. What are the different roof deck attachment discount categories for a wind mitigation inspection?

  33. What is the difference between roofing felt and synthetic underlayment?

  34. Why is a popped nail in a shingle roof a problem? How do I fix it?

  35. What is engineered wood siding?

  36. Are roof trusses better than roof rafters (stick framing)?

  37. What are the hazards to avoid when going into an attic?

  38. How can I tell if a roof has more than one layer of shingles?

Welcome to our blog!
We want you to be an informed homebuyer, and each blog post is a question that we have answered for our friends and customers over the years. Hope they help you make a good choice for your next home.

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
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