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Split Roof Ridge Board

Split Roof Ridge Board

Split Roof Ridge Board


I’ve been renting this 1 story house right outside Wichita Kansas built in 1910 for a few months now and finally decided to poke my head and flashlight up into the attic. In the attached picture, hopefully you can see that the ridge board is severely split in half down the grain. This occurs right about midpoint of the roof length. The split only seems to extend the distance between two rafters; however, I expect this to only worsen over time. The owners are quite old and like to do things themselves so there are little to no changes to the building regarding structure. So, do you think this is an urgent issue that I should bring to their attention immediately as a structural emergency? Thank you for your input!

RE: Split Roof Ridge Board

A ridge board, with the ceiling framing below acting as a tension tie, is nearly non-structural and of nowhere near the importance of a a true ridge beam. As such, I don't see significant risk here. That said, I recommend having a local structural engineer come out and review the situation if you are not such an engineer yourself.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me: http://www.eng-tips.com/viewthread.cfm?qid=456235

RE: Split Roof Ridge Board

I agree with KootK as long as the ceiling joists ARE actually tying the rafters together. If they run parallel to the rafters and are attached to the sides of the rafters in some meaningful way then you are probably good.

RE: Split Roof Ridge Board

The ridge split may be related to the stiffleg in the picture. I can't tell for sure, but the rafter looks like 2x4 rafters that were used a lot in older buildings. In modern houses, 2x4s only span a horizontal distance of about 7' if you do not have heavy snow loads. Any normal roof sag that may have tried to occur would have been resisted by the stiffleg. If the stiffleg was connected to the ridge, it could have split it.

Some houses as old as you are noting in my area were built without any ridge board. The rafters nailed to each other and that was it.

RE: Split Roof Ridge Board

For some reason, ridge boards, ridge beams, their function, and and the reasonableness of the absence of them, is a subject completely baffling to 99% of the general population and 100% of building department staff.

Despite the fact that the OBC and NBCC (and I would guess American codes too) specifically state when, where, and how they are required, it is a mystery to so many.

I think all 3 eminent posters above are right; I'd be very surprised if the ceiling joists aren't tying the rafters and if the vertical leg isn't the cause of the split. The leg is pretty skinny, it might have been beside a vent or something for some reason, or else why is the original roof sheathing cut out?

RE: Split Roof Ridge Board

Having been a framing carpenter, the ridge board seemed like something to make construction easier more than provide some strength aspect. The early years there was no ridge board. I have built roofs with ridge boards and without them. Originally, your rafters had to nail to each other and stay in place under wind until you got the roof deck on. By adding the ridge board, you could nail rafters to it and laterally brace one place along the ridge that would brace all rafters simultaneously. This also kept the rafters spaced apart correctly whereas the no ridge board method did not.

One last thing it does that may not be by design is that it is providing a stiff member along the ridge. I have seen really old buildings where the roof decking has sagged with age due to wide rafter spans such as 30" to 36". The addition of the ridge board keeps the total length of the ridge the same rather than getting less due to the additive nature of the multiple sagged decking sections.

Another ease of construction is the fact you have to plumb the rafters before you can deck the roof. Adding the ridge board made plumbing the rafters a lot easier than when there was no ridge board. The cost of the ridge board was easily made up for in labor. Remember also, the early ridge boards were 3/4" lumber. No real strength. Now we use 1.5" lumber and have a rule the depth of ridge must be equal or greater than the cut end of the rafter.

RE: Split Roof Ridge Board

Quote (JHoll97)

The owners are quite old and like to do things themselves so there are little to no changes to the building regarding structure

There has definitely been some structural modifications - I doubt the OSB roof sheathing is original from 1910 bigsmile. Agree with others that the split probably isn't a structural concern.

RE: Split Roof Ridge Board

Ron247 knows exactly what the ridge board is for: it makes for easier framing.

RE: Split Roof Ridge Board

I’ve looked at a number of older houses like this and have seen similar issues, either damage to the ridge board or buckling of a brace supporting the ridge board. As others have said, the ridge board theoretically don’t typically have a structural function. In my opinion, the reality is that the tension tie that should be created by the ceiling joists is often lacking in connection strength require to resist the design thrust forces. Of course the design loads are usually much larger than realistic loads. But The odds are that your roof is technically under-framed, and it would probably require a good amount of remediation to bring it up to code. As Kootk said, the best thing would be to have a structuring engineer take a look at it and get their thoughts. What they are going to look for is noticeable deflection in the roof system, buckling or failure of structural members, and separation of connections, as well as anything that is obviously structurally inadequate.

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