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California Roof Framing Techniques

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When one roof is framed on top of another, already existing roof, this type of roof framing is sometimes called "California" roof framing. I refer to the roof that is framed first as the "existing roof" and the roof that will be framed on top of it as the "California roof". Sometimes I sheath the existing roof before framing the California roof and also add a "flat valley board", ( usally a 2" x 12" ) to nail the California jack rafters to. Other times, I nail the flat valley board directly to the top of the existing roof rafters and add blocking for the plywood at the valley.

I'd like some feedback from you guys who do a lot of this type of framing. Do you Always, Sometimes, or Never sheath the existing roof before framing the California roof? Is it required by the building codes in your area? Do you add a flat laydown valley board to nail the California jack rafters to, or do you nail them directly to the plywood sheathing? If you use a flat valley board, what type of stock do you normally use for it? Do you ever nail the valley board directly to the top of the existing rafters? If so, do you add blocking at the valley?

In your area, what other names are used for this type of roof framing besides "California"? Also, in south Texas, you don't "sheath" a roof, you "deck" it. What do you call this process in your area?

(post #177575, reply #1 of 9)

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Ken - Where I run into this most often is on additions, but I have also done it a few times on new framing. I have always used 2 2X6s for that "flat valley board", one at the heal of the "California" rafters and one at the points. I never have called those boards any name, or heard them referred to out loud.

It seems questionable to me to bear the "California" rafters directly on the sheathing, especially if you don't block. Certainly on anything sheathed with CDX or OSB, I would use those flat valley boards. - jb

(post #177575, reply #2 of 9)

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Thanks Jim,

I agree that the California jacks shouldn't bear directly upon the sheathing ( especially when 24" O.C. ), but many that I've talked to do just that ( get in get out attitude ).

BTW, the blocking that I was referring to, when nailing the flat valley board directly to the existing roof rafters, would be nailed below the flat valley board to give support to the ply (sheathing/decking) of the existing roof.

More comments welcome. Thanks

(post #177575, reply #3 of 9)

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Oh. I thought you meant to block below the sheathing and then land the new rafters right on the sheathing, which seems marginal, but better than no blocking. I don't think you need blocking beneath the sheathing if you have the flat valley framing on top. Wouldn't hurt, but I don't see that it's needed - jb

(post #177575, reply #4 of 9)

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Ken:

I'm far from an expert but let me share what I know about roof overframes in my geography. Around here we call them blind valleys. All that I have seen were built on top of the main roof's sheathing.

For stick built roofs, the "flat" valley board (installed on top of the sheathing) varies in size depending of the overframe's rafter size and slope. Usually 2x6 or 2x8, since larger roofs/rafters are not built in this manner, but rather with conventional valleys. For stick framed overframes, inspectors in our area look explicitly for the flat valley board, and if it's not in there, oh s*@t!! They require some kind of access, so that they can look up in there for the valley board and the collar ties. All our house plans are required to be engineered, so little is left for interpretation in the field.

Just as a matter of interest, trussed roofs are few and far between around here except for with the very high volume builders. These often use blind valleys, and sometimes the truss engineering sheets specify blocking instead of the flat valley boards if the overframe is trussed. (PE's rule) Other trussed overframes, don't require blocking or valley boards, I suspect because the overframe truss point load bears directly on a truss's top cord below. The trusses are always 24" O.C.

BTW - the 3 slope bastard hip roof you advised me on about 6 months ago came out fine. Thanks

(post #177575, reply #5 of 9)

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Ken,

In my area they are refered to as overframes. We run the sheathing and then use a flat valley board-a 2x12. All the rafters i see are 2x12 or stronger members. If the roof is a low pitch I usually run a 2x6 on the inside of the 2 x12 to make sure the level cut has plenty of bearing.

One thing I run into often with overframe dormers is that they change to true valleys past the wall line. I will either support the overhanging valley with a subfascia or run the flat valley and the ridge long and then attach the last rafter at the correct distance off the house.

(post #177575, reply #6 of 9)

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The flat valley board or the board to receive the rafter is often called out west the; sole plate and sometimes referred to as a sleeper.In Boise Idaho this plate does not have to be directly underneath the rafters. It can be applied to the sheating up to where it's edge touches the edge of the rafter, basically to the bottom edge of the sloped cut. I guess they figure that with a 45# psf snow lding we didn't need to do it the right way!(oh ya I forgot to mention that a 2x4 is adequate enough)

Rob

(post #177575, reply #7 of 9)

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Rob,

I just finished reading your post for the third time and I'm still not sure that I inderstand what you mean by the "sole plate" or the "sleeper".

You say that it doesn't need to be directly underneath the rafters. Also that it cna be a 2 x 4 applied to the sheathing. What purpose woild it serve if nailed to the exixting roof in this manner?

Please clarify. Also, by the "bottom edge of the sloped cut" are you referring to the level cut that is made on the bottom end of the valley jacks?

(post #177575, reply #8 of 9)

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Ken,

you are correct in asking what purpose it would serve?. I guess they figure that in order for the bottom end of the jacks to be pushed thru the existing roof sheating, the 2x4 would have to be sheared thru first.

and yes I was referring to the level cut/bevel cut.The 2x4 is underneath the overbuild/california slid up to the bottom of each and every rafter and nailed over the existing sheating.(basically a knife edge connection)

Personally I dont really like this method that much. However I do use it as an acceptable building practice.

Rob

(post #177575, reply #9 of 9)

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Infill framing is a term I've seen,
but I'm from California. I've been wondering myself if california framing was a west coast term.

I'm looking at a detail by a local engineer now.

"2x6 Sleeper with (2) 10d each top chord" is noted. This is where the upper plywood is "edge nailed" into the flat 2x6, which is in turn nailed into the truss roof below. The flat 2x6 serves to distribute the load of the rafter ends above into the lower roof, so that the plywood doesn't deflect too much, and also makes a good shear connection between the two different plywood planes.

The detail notes "2x6 rafters at california framing".

"Carry plywood under" is noted at the lower truss roof.

I wonder if "california framing" is sort of like a "Hollywood stop". That is, something that is done for looks and is not real...

Gary Wheeler, AIA