Shed Rafter Detail

timber frame shed rafter detail for a porch


Using a ledger, a post and plate system along with shed common rafters is a fast and effective way to construct an exterior porch or storage area.  In this shed rafter detail, the 4×8 rafters are housed into the upper ledger 3/4 inch and secured with an 8 inch structural screw.  At the plate, the rafters are housed on the outside of the plate 3/4 inch and secured with at least a 10-inch structural screw.  The housings are added not only for added strength but to ensure the cleanest looking joinery for years to come.

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9 thoughts on “Shed Rafter Detail”

  1. This seems to be an effective way to design and build an exterior timber framed porch. I am concerned with mounting this ledger board properly to the wall given that my walls have 1.5″ rigid foam on the exterior. Do you have a method for doing this without creating a thermal bridge in the external insulation plane?

  2. That is a tough one. Cannot think of a way to completely not pierce the insulation plan. You can minimize this it by adding half posts under the ledger to create a free-standing structure, but even then you are going to want to join it to the main house or building with some fasteners. Would love to hear what your solution finally is.

  3. The max ledger height I can get on my structure is 9.5 feet. What is the minimum roof pitch you would recommend? Im in middle TN and the most snow I have seen on the ground here in 25 yrs is 8 inches.

  4. I am looking to use this design to attach a 12′ porch to a 64′ side of my pole barn.

    I will be using 6×6 post at 10′ on center with doubled up posts on each end to make up the 4 foot of diference.

    What are the dimensions of the Ledger beam and Plate I should use for 10′ spans. I am going to attach the ledger at each 8 ft post in the building. Also using 4×10 in rafters what is the recomended spacing for a 2:12 pitch roof. I will be using 2×4 purlins spaced 24″ OC across the rafters with 29 gauge ribbed metal roofing.

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