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Back Yard · U-Bed Build · Wall Detail

Wall Cross-Section, HDPE Liner in Place

Vertical section through the cedar wall at the finished state
What This Shows

Vertical section through the cedar wall at the finished state. Shows the full layer stack-up: mower strip trench, below-grade cedar, hardware cloth wrap, HDPE liner, cap strip, and soil column.

Section A-A · Looking North
Wall Detail at Arm
C4 C3 C2 C1 staple 2" overlap 20" exposed wall 5.5" 5.5" 5.5" 3.5"* *below grade 2" bury 3/4" 1.5" 12" mower strip trench 3" 1 2 3 4 5 6 7 8 Cedar cap strip 3/4" × 1.5" · screw 12" O.C. HDPE fold-over 1" lap onto top of course 4 Top-edge staples 1/2" stainless · 6" O.C. 30 mil HDPE liner Interior wall face · full height Cedar 2×6 wall 4 courses on edge · 3.5" stainless screws Wall-face staples 1/2" stainless · 8-10" O.C. vertical 1/4" hardware cloth Base + 4" wall wrap · vole barrier Mower strip 12" × 3" · fabric + 1.5" river rock A B C A B C Garden soil mix 40% compost / 40% topsoil / 20% perlite Hugel base 8" Norway Maple logs + organic fill Native ground Undisturbed below hardware cloth KEY PLAN A A N ← EXTERIOR INTERIOR (BED) → WALL ℄
Manor U-Bed · Wall Detail A-A · Drawing S-01 Rev 2 · Scale 1 in = 20 px · Build reference
1 Install Sequence at This Section
Install Sequence
  • Dig the 12 in x 3 in mower strip trench and level the bed footprint.
  • Set cedar 2x6 course 1 with about 2 in below grade (supports the wall and hides fasteners).
  • Staple 1/4 in hardware cloth across the full interior base, wrapping up the inside face of course 1 about 4 in.
  • Stack courses 2-4, screwing to 4x4 corner posts with 3.5 in stainless.
  • Drape 30 mil HDPE down the interior face of all four courses, overlapping the hardware cloth wrap by about 2 in.
  • Staple liner to the interior face 8-10 in on center vertically, then fold 1 in over the top of course 4 and staple 6 in on center.
  • Rip a 3/4 in x 1.5 in cedar cap strip from scrap and screw down 12 in on center to permanently trap the liner fold.
  • Fill: 8 in Norway Maple hugel base, then garden soil mix to just below cap height.
2 Critical Notes and Assumptions
Critical Notes and Assumptions Read Before Building
  • Do NOT line the base with HDPE. Drainage must stay open through the hardware cloth, the liner is a wall treatment only.
  • HDPE, not PVC. PVC pond liner off-gasses plasticizers and is not food-safe.
  • Wall height math: four 2x6 on edge = 22 in actual (5.5 in per course). With the bottom course buried 2 in for anchoring, exposed height is 20 in per build-guide spec.
  • Cap strip dimensions (3/4 in x 1.5 in) are a recommendation, the build guide calls for a cedar cap strip without specifying. Ripping from 2x6 scrap is easiest.
  • Staple spacing (6 in top, 8-10 in faces) is industry standard for 30 mil HDPE; the build guide does not specify on center.
  • Hardware cloth wrap-up (4 in onto the course 1 interior face) overlaps the HDPE bottom by 2 in, this detail keeps voles out and stops soil from getting under the liner.
The Manor · Back Yard · U-Bed Wall Detail Drawing S-01 Rev 2 · build reference