Roof Deck & Edge Details

Deck sheet layout (each slope)

Each slope is 151-1/4″ long (ridge 143-13/16″ plus 3-3/4″ past each end rafter) and 71-1/4″ from the eave edge to the ridge center, measured along the slope. The lower course is full-width sheets; the upper course is strips ripped from one sheet. The end seam lands on the middle rafter (rafter 4, center 72-3/4″ from the south end of the building). 3 sheets per slope, 6 total, plus your spare.

• Measure before cutting the upper strips: after the lower course is nailed, measure from its top edge to the ridge center line at both ends. Subtract 1/8″ for the gap. The 23-3/16″ shown assumes 47.9″-wide sheets and 3-3/4″ edge overhangs.
• Lower course edge line: the deck's bottom edge sits 3-3/4″ outside the wall line (horizontally), which is 4-1/8″ past the rafter's top corner, measured along the rafter. Mark that on both end rafters and string a line.
• Rake overhang: the sheets run 3-3/4″ past the outside face of each end rafter.
• Nailing: 3″ ring gun nails, 4″ apart on sheet ends and the end rafters, 6″ on the others, into rafters only. No nails in the overhangs.

Eave detail (east and west walls)

• Why the shadow and fascia tops are 2-1/2″ above the plate: the deck slopes down toward the edge. The shadow board's outer top corner is the point that touches the deck. With square-cut tops, the fascia sits flush with it. That leaves a wedge gap above the fascia (up to about 1-5/8″ at the wall), which the eave enclosure closes later.
• Option: raise the fascia about 7/8″ so its own outer corner also touches the deck. That shrinks the gap, but shows 7/8″ less fascia below the shadow board (about 2-7/8″ instead of 3-3/4″). Your call.
• Drip edge fit (corrected Oct 1): use a standard ~90° drip edge as is; don't bend it. Its face is square to the deck, so on 6:12 it leans slightly back: it lies flat against the square-cut deck edge and rests on the shadow board's top corner, with the kick throwing water clear. Keep the deck's eave edges square. A plumb-bevelled edge, suggested earlier, would leave a gap behind it.
• What shows from below: about 1-1/4″ of black drip edge, about 2-7/8″ of shadow board, then about 3-3/4″ of fascia.

Rake detail (north and south gables)

• What the rake fascia attaches to: the end rafter, through the gable plywood. Its top is tight under the deck, so it covers the rafter's 5-1/2″ depth plus about 2″ below. Screws go through the fascia and plywood into the rafter. The shadow board screws into the fascia.
• At the peak, the two rake fascia boards meet with the same 6:12 plumb cut as the rafters, and so do the two shadow boards.
• At the eave corner (flush, decided Oct 4, 2026): the eave fascia and eave shadow board both end at the gable plywood + band face, about 144-3/4″ long. The rake fascia and rake shadow board both run out over those ends to the eave shadow board's face (~3-3/4″ past the wall), plumb-cut flush there. If a 12′ eave board is short, center it (up to ~1/8″ shadow line per end) or glue a cedar filler on the end. Not the JCS stepped corner, which would need ~147-3/4″ eave shadow boards. Fit in place.
• Length: each rake fascia is about 71-1/4″ along its top edge. That's why you have one 12′ board per rake: two won't nest on one board.

Eave–rake corners (flush, decided Oct 4, 2026)

How the eave trim and rake trim meet at the four lower corners. Flush corners use the trim boards you already have; the JCS stepped corner would need eave shadow boards about 147-3/4″ long.

What to watch for

• Eave board length: the eave fascia and eave shadow board each need about 144-3/4″: the 143-13/16″ wall plus about 1/2″ of gable plywood and band at each end. A nominal 12′ board is often 144-1/4″ to 145″, so measure each board before cutting.
• If a board is short: center it so the shortfall splits between the two ends. Up to about 1/8″ per end reads as a thin shadow line and can be caulked. More than that: glue and screw a cedar filler block on the end, cut from spare stock, so it's tight to the rake fascia.
• Sequence: the eave trim goes on before the gable plywood (Build Guide step 8, then step 9). Cut the eave boards to the framing length plus the plywood + band allowance at each end; check the allowance with a scrap of the gable plywood and band held at the corner.
• Rake board lower ends: plumb-cut flush with the eave shadow board's face, 3-3/4″ past the wall framing. Optionally add a level cut on the rake fascia so its bottom lines up with the eave fascia's bottom; otherwise the rake fascia hangs about 7/8″ lower at the outer corner.
• Exposed sliver: a small triangle of eave-fascia end grain, about 3/4″ tall at the inside face and tapering to nothing, shows below the rake fascia. Paint or caulk it. If the eave fascia is raised ~7/8″ (the open eave decision), the rake fascia covers it completely.
• Green cedar: fit the corners in place and make the final end cuts after the boards have settled.

Ridge detail

• Confirm at raising: the ridge is cut and the test pair fitted. Check that each rafter's top is flush with the ridge top at its faces. The heights on this page assume so.
• Ridge-end connection: the RR-R doesn't fit at the ends. Use A35Z angles there: one leg on the rafter face, one on the ridge face, 12 SD9112 each.

Temporary ridge props

• Ridge bottom: 26-3/4″ above the plate top (104-1/4″ above the floor). Ridge top: 34″ above the plate.
• Post: a 2×4 at 30-1/4″, screwed to the inside face of the gable top plate with 4 screws, its bottom flush with the plate bottom. Add a scrap cleat on top so the ridge can't slide off.
• Check that the ridge is level end to end once it's on the props, before setting rafters. The props come out after the collar ties are in and the deck is nailed off.

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