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Shimmed Rafters & Ridge Board


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I had a one year warranty inspection today. Several of the rafters were shimmed at the ridge beam. I couldn't see the endbearing because insulation blocked that area and the path to it.

The house had a really complex roof structure, all conventional rafters. This section was maybe 10-12 feet wide but the rafters were easily 20 feet long. There's a slate roof on the plywood sheathing.

Is this a problem? If so, what's the fix?


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When the rafters were installed, full bearing against the ridge board was required.

As far as a code compliant repair I don't see why one can't install a bearing plate made out of plywood or OSB or a 1"x and fasten everything together with a proper framing connector/hanger etc.

If the end of the rafter was split then a code compliant repair might call for sistering up another rafter from point of bearing to point of bearing.

However the code gods might say different.

Chris, Oregon

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I must admit I have never seen shims used like that! I don't have a clue as to what needs to be done or how it could be done. The more I look at that I just have to wonder if the rafters pulled away from the weight of the shingles after the roof was on.

And what is that copper line along the bottom of the ridge? Please don't tell me that this from a lighting rod!

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It looks to me like the framer cut the rafters too short and this was the "Solution" to the problem.

This should have been caught during the framing inspection, full bearing is required at the ridge.

Are there collar ties? Knee walls?

Are there any signs of movement? Sags?

A 20 foot rafter span is very long, especially when it snows. More info and analysis are needed to determine the proper fix.

It is a problem but it may not be an expensive repair. Too many variables to accurately answer what is needed.

Good catch!

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And what is that copper line along the bottom of the ridge? Please don't tell me that this from a lighting rod!

OK Scott, I won't tell you that. Btw, do you have any idea of what these thin, rod-like metal things attached to the chimney pots might be? [;)]

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I didn't look very carefully the first time and I missed that the ridge board is not deep enough either!

At least they got close on that one. Now this is bad:

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Are there collar ties? Knee walls?

No knee walls, but there are fullsize collar ties (which is somewhat of a rarity around here).

Can't see any fasteners. 2 -16D's required. Were they just on the other side of the rafters?

They were end nailed. You can see a nail in the closer one.

Theres one rafter sistered. Why? and was that done properly.

Yikes! I didn't even see that. I can't imagine why they'd sister two pieces of 3/4" stock.

I sure had my hands full today. I spent about an hour on the roof alone. Lovely workmanship for $1,800,000 eh?

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  • 2 weeks later...

I'm currently in a argument with a builder over this same situation, i.e. multiple rafters have no bearing whatever on the ridge board. I've searched our state code--which is wicked similar to CABO--and can find nothing which definitively states that the rafters must fully bear against the ridge. Does anyone know of any codes or standards of practice that mandate a positive connection?

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Ask the builder to show the homeowner one illustration in any framing book where it shows rafters not bearing fully on a ridge board with full contact. He won't be able to. It's not a joint unless there is full contact. If the builder is defending that kind of workmanship, he's an idiot and an incompetent hack.

Better yet, tell him to pose that question on my building science forum on JLC and I'll tell him that personally.



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