# Three-tier back deck — 32'-0" × 24'-0" overall, freestanding. # # Demonstrates SHARED POSTS between tiers: a post on a tier line carries # the upper tier's beam near its top and the lower tier's beam partway # down, so one 6x6 serves two levels. Look at P6, P12, P13 and P16 in # the ISO — they run past one deck to reach the next. # # Tier 2 bears at 1'-5-3/4" and not a round 1'-8": its beam shares the y=10 # posts with T1-S, and at 1'-8" the two would have overlapped in elevation by # 2-1/4". Two 3" beams cannot occupy the same wood in a 5-1/2" post. Dropped # to 1'-5-3/4", T2-N's top lands exactly on T1-S's underside and P6, P7, P8 # and P11 carry two pockets stacked in one face. The step it costs is real # and the FINDINGS panel prices it in risers. # # Elevations here are INPUTS ONLY — bottom-of-beam (bearing_ft) per tier: # Tier 1 bearing 2'-3" (at the house) # Tier 2 bearing 1'-5-3/4" # Tier 3 bearing 0'-4" # # Tiers 1 and 2 are FLUSH framed (joists hung between the beams in # hangers). Tier 3 is DROP framed (joists run over the top of its beams), # so its deck sits a full joist depth above its beam tops and it takes # hurricane ties instead of hangers — and its rims sit at joist level # (top_ft), nailed to the joist ends rather than hung between the beams. # # Deck tops, post cut lengths and the step between tiers are all DERIVED # from those bearings plus each member's section depth. Read them off the # TAKEOFF and FINDINGS panels — never from a comment. Restating a derived # number in prose is how a model and its output drift apart. # 2by's libraries this design is checked against (docs/materials-plan.md): # no revision, so a demo always follows 2by's current ones. materials: { lumber: southern-pine, hardware: simpson } project: slug: tiered-deck title: Three-Tier Back Deck revision: r3 date: 2026-09-02 live_psf: 40 dead_psf: 10 allowable_psf: 1500 waste_pct: 10 bearing_ft: 2'-3" # No slab under a deck — every post gets its own pier, so all posts are # marked perimeter: false and the foundation panel calls them all out. slab: field_in: 0 perimeter_in: 0 perimeter_width_in: 0 phases: - id: p1 name: Upper + Middle Tier - id: p2 name: Lower Tier # STOCK OVERRIDE, kept deliberately. Lengths normally live in the LUMBER file # and every model reads them from there. This job is buying from a yard with a # thinner rack — 2x8 in 8 and 12 only, 6x6 in 12 only — so it states its own # and the tool reports each override in the Findings. It is also what makes # this model's cut list interesting: a constrained rack is where nesting and # offcut actually cost money. stock: 2x8: [8, 12] 2x10: [10, 12, 16] 6x6: [12] posts: # --- house side, y = 0 (tier 1 north beam) - id: P1 at: [0, 0] size: 6x6 phase: p1 perimeter: false - id: P2 at: [8, 0] size: 6x6 phase: p1 perimeter: false - id: P3 at: [16, 0] size: 6x6 phase: p1 perimeter: false - id: P4 at: [24, 0] size: 6x6 phase: p1 perimeter: false - id: P5 at: [32, 0] size: 6x6 phase: p1 perimeter: false # --- tier 1 / tier 2 line, y = 10'-0" (SHARED POSTS, two elevations) - id: P6 at: [0, 10] size: 6x6 phase: p1 perimeter: false - id: P7 at: [8, 10] size: 6x6 phase: p1 perimeter: false - id: P8 at: [16, 10] size: 6x6 phase: p1 perimeter: false - id: P9 at: [24, 10] size: 6x6 phase: p1 perimeter: false - id: P10 at: [32, 10] size: 6x6 phase: p1 perimeter: false - id: P11 at: [20, 10] size: 6x6 phase: p1 perimeter: false # --- tier 2 / tier 3 line, y = 18'-0" (SHARED POSTS, two elevations) - id: P12 at: [0, 18] size: 6x6 phase: p1 perimeter: false - id: P16 at: [6, 18] size: 6x6 phase: p1 perimeter: false - id: P13 at: [12, 18] size: 6x6 phase: p1 perimeter: false - id: P14 at: [20, 18] size: 6x6 phase: p1 perimeter: false # --- lower tier outer edge, y = 24'-0" - id: P17 at: [0, 24] size: 6x6 phase: p2 perimeter: false - id: P18 at: [6, 24] size: 6x6 phase: p2 perimeter: false - id: P19 at: [12, 24] size: 6x6 phase: p2 perimeter: false beams: # ---------------- TIER 1 · bearing 2'-3" ---------------- - id: T1-N label: Tier 1 house beam axis: x supports: [P1, P2, P3, P4, P5] plies: 2 section: 2x10 trib_ft: 5 bearing_ft: 2'-3" phase: p1 - id: T1-S label: Tier 1 outer beam axis: x supports: [P6, P7, P8, P11, P9, P10] plies: 2 section: 2x10 trib_ft: 5 bearing_ft: 2'-3" phase: p1 - id: T1-RW label: Tier 1 west rim axis: y supports: [P1, P6] plies: 1 section: 2x10 trib_ft: 0 bearing_ft: 2'-3" phase: p1 - id: T1-RE label: Tier 1 east rim axis: y supports: [P5, P10] plies: 1 section: 2x10 trib_ft: 0 bearing_ft: 2'-3" phase: p1 # ---------------- TIER 2 · bearing 1'-8" ---------------- - id: T2-N label: Tier 2 upper beam axis: x supports: [P6, P7, P8, P11] plies: 2 section: 2x10 trib_ft: 4 bearing_ft: 1'-5-3/4" phase: p1 - id: T2-S label: Tier 2 outer beam axis: x supports: [P12, P16, P13, P14] plies: 2 section: 2x10 trib_ft: 4 bearing_ft: 1'-5-3/4" phase: p1 - id: T2-RW label: Tier 2 west rim axis: y supports: [P6, P12] plies: 1 section: 2x10 trib_ft: 0 bearing_ft: 1'-5-3/4" phase: p1 - id: T2-RE label: Tier 2 east rim axis: y supports: [P11, P14] plies: 1 section: 2x10 trib_ft: 0 bearing_ft: 1'-5-3/4" phase: p1 # ---------------- TIER 3 · bearing 0'-4" ---------------- - id: T3-N label: Tier 3 upper beam axis: x supports: [P12, P16, P13] plies: 2 section: 2x8 trib_ft: 3 bearing_ft: 0'-4" phase: p2 - id: T3-S label: Tier 3 outer beam axis: x supports: [P17, P18, P19] plies: 2 section: 2x8 trib_ft: 3 bearing_ft: 0'-4" phase: p2 - id: T3-RW label: Tier 3 west rim axis: y supports: [P12, P17] plies: 1 section: 2x8 trib_ft: 0 top_ft: 1'-6-1/2" # joist level, not beam level — T3 is drop framed phase: p2 - id: T3-RE label: Tier 3 east rim axis: y supports: [P13, P19] plies: 1 section: 2x8 trib_ft: 0 top_ft: 1'-6-1/2" # joist level, not beam level — T3 is drop framed phase: p2 joist_fields: - id: T1 label: Tier 1 section: 2x10 span_axis: y bounds_x: [0, 32] bounds_y: [0, 10] framing: flush spacing_in: 16 bears_on: [T1-N, T1-S] blocking: true phase: p1 - id: T2 label: Tier 2 section: 2x10 span_axis: y bounds_x: [0, 20] bounds_y: [10, 18] framing: flush spacing_in: 16 bears_on: [T2-N, T2-S] blocking: true phase: p1 - id: T3 label: Tier 3 section: 2x8 span_axis: y bounds_x: [0, 12] bounds_y: [18, 24] framing: drop # joists run OVER these beams — deck sits a joist depth higher spacing_in: 16 bears_on: [T3-N, T3-S] blocking: true phase: p2 connections: # ---- tier 1 notched bearings - at: P1 member: T1-N type: notch - at: P2 member: T1-N type: notch - at: P3 member: T1-N type: notch - at: P4 member: T1-N type: notch - at: P5 member: T1-N type: notch - at: P6 member: T1-S type: notch - at: P7 member: T1-S type: notch - at: P8 member: T1-S type: notch - at: P11 member: T1-S type: notch - at: P9 member: T1-S type: notch - at: P10 member: T1-S type: notch # ---- tier 2 notched bearings (lower notch, same posts at y=10) - at: P12 member: T2-S type: notch - at: P16 member: T2-S type: notch - at: P13 member: T2-S type: notch - at: P14 member: T2-S type: notch # ---- tier 2 upper beam, stacked under T1-S on the same posts - at: P6 member: T2-N type: notch - at: P7 member: T2-N type: notch - at: P8 member: T2-N type: notch - at: P11 member: T2-N type: notch # ---- tier 3 notched bearings (lower notch, same posts at y=18) - at: P12 member: T3-N type: notch - at: P16 member: T3-N type: notch - at: P13 member: T3-N type: notch - at: P17 member: T3-S type: notch - at: P18 member: T3-S type: notch - at: P19 member: T3-S type: notch # ---- rims hung, never notched, so no post is ever cross-notched - at: P1 member: T1-RW type: hung into: T1-N part: LU210 - at: P6 member: T1-RW type: hung into: T1-S part: LU210 - at: P5 member: T1-RE type: hung into: T1-N part: LU210 - at: P10 member: T1-RE type: hung into: T1-S part: LU210 - at: P6 member: T2-RW type: hung into: T2-N part: LU210 - at: P12 member: T2-RW type: hung into: T2-S part: LU210 - at: P11 member: T2-RE type: hung into: T2-N part: LU210 - at: P14 member: T2-RE type: hung into: T2-S part: LU210 # T3's rims are drop-framed: they nail to the joist ENDS at joist level, # so they take no hanger. Only the flush tiers above use LU210/LU28.