A No-Math Approach to Valley Plates

Synopsis: In roof framing, valley plates are used most commonly when framing layover gable dormers or chimney crickets as a means of attaching the new framing to the existing sheathing and rafters, and to provide a place for the valley jacks to land, but framing the valley plate can be pretty confusing. This series of step-by-step instructions and drawings by John Carroll and Chuck Lockhart [repurposed from The Complete Visual Guide to Building a House (The Taunton Press, 2014)] gives one approach to valley-plate and valley-jack layout and installation.

Depending on where you live, and who you’re framing with, you’ll hear valley plates called a lot of different names: valley boards, blind valleys, California valleys, reverse valleys, layover valleys, false valleys, and sleepers. Valley plates are used most commonly when framing layover gable dormers or chimney crickets as a means of attaching the new framing to the existing sheathing and rafters, and to provide a place for the valley jacks to land. Compared to laying out and installing the ridge board and common rafters, framing the valley plate can be pretty confusing. It’s possible to figure the layout using geometry— the valley plate is essentially the hypotenuse of an imaginary triangle laid flat on the roof deck. But I prefer to avoid the math, instead relying on stringlines, measurements, and some creative marking in place

Lay out and install the valley plate

The valley jack rafters need to rest on a plate. The plate doesn’t need to be beveled, but because of its thickness, you need to install it inside the valley line; the object is to get the top outside edge of the plate in plane with the tops of the common rafters.

From Fine Homebuilding #284

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More about valley plates:

• Framing a Roof Valley – Getting these rafters right is important.
• Valley Framing: Calculating the Jack-Rafter Assignment – All about framing, valley jacks, and rafters.