Under-Stair Storage Shelf

Dimensions

Cut list

Tools you'll need

• ✓

  Measuring Tape (5m or longer)

  Used for measuring each material

• ✓

  Pencil and Carpenter's Square

  For marking lines and checking right angles

• ✓

  Saw

  Use home center cutting service recommended

• ✓

  Electric Driver

  Impact driver improves work efficiency

• ✓

  Sandpaper

  Prepare two types: #120 and #240

• ✓

  Level

  Essential for checking horizontality during assembly

• ✓

  Clamps (2 or more)

  Used for temporary fixing during joining

• ✓

  Brush and Paint Tray

  Used for oil and varnish finishing

Materials

Build steps

1. 1

   Final Check of Materials and Tools

   ≈ 15 min

   Prepare 2 side boards of SPF lumber 1x10 (19×400×800mm), 6 shelf boards (19×400×1500mm), 1 plywood back panel 4mm thick (1500×800mm), 16 coarse-thread screws 38mm, and 4 L-shaped brackets 50mm. Tools include electric driver, saw, measuring tape, carpenter's square, #120/#240 sandpaper, level, 2 F-clamps, brush and paint tray, and a stapler or fine nails.

   Measure

   W 1500 mm

   MeasureSTEP 1 / 20

   Tip

   • SPF lumber tends to warp. Check each piece visually when purchasing; select boards with warp within 1mm.
   • L-shaped brackets and screws are the lifeline for tip-over prevention. Do not omit them.

   Watch out

   • Check each SPF board for warp, cracking and knots before purchasing. Using boards warped more than 1mm causes shelf distortion.
   • The 4mm plywood back panel is thin and prone to breaking when moved. After cutting, store it standing up immediately.
2. 2

   Secure Workspace

   ≈ 10 min

   Find a workspace where you can stand and work on an 800mm high bookshelf. Ceiling height should be 2200mm or more, floor area about 1500×1200mm is sufficient. Lay a blue sheet and support long boards on two sawhorses.

   Inspect

   No wobble ✓

   InspectSTEP 2 / 20

   Tip

   • Assemble the bookshelf lying down on the floor. Stand it up only in the final step. Can be done in small rooms.

   Watch out

   • Standing up the completed bookshelf is difficult alone. Two people recommended for safety.
   • Ceiling heights under 2000mm will hit the ceiling when standing bookshelves up. Confirm in advance.
3. 3

   Make Cut List and Request Cutting

   ≈ 20 min

   Submit a cut list to the home center for cutting: 2 side boards (800mm), 6 shelf boards (1500mm), and 1 back panel (1500×800mm). If cutting yourself, support long boards (800mm) on two sawhorses and cut by pulling the saw. Aim for cutting tolerances within ±2mm.

   Cut

   Use the in-store cut service

   CutSTEP 3 / 20

   Tip

   • Cutting costs 30-50 yen per cut. Entire cutting service costs about 1000 yen, reducing time from 30 minutes to immediate.
   • Bundling 6 shelf boards of the same dimensions to cut all at once yields the most accuracy.

   Watch out

   • 19mm thick SPF lumber warps easily even when cut straight. Use guides to cut straight.
   • 4mm plywood is soft and tends to bend and warp if not supported underneath during cutting.
4. 4

   Sand All Materials (#120 to #240)

   ≈ 40 min

   Sand all materials starting with #120 grit then finish with #240. Pay special attention to sanding shelf ledges on side boards, top and bottom surfaces of shelf boards, and wood edges (ends). Rounding shelf edges where hands touch makes handling easier. After sanding, vacuum to remove all sawdust.

   Sand

   #120

   SandSTEP 4 / 20

   Tip

   • Sanding shelf boards smooth helps smooth book insertion and removal.
   • Wood edges (cut surfaces) tend to have raised grain; sand carefully starting from #120 grit.

   Watch out

   • SPF lumber is soft; sanding too much changes dimensions. Use #120 primarily and #240 only for finishing.
   • Over-rounding edges looks unsightly; keep radius around 2mm.
5. 5

   Mark Shelf Positions on Side Boards

   ≈ 15 min

   Place two side boards side-by-side and mark positions for 6 shelves with a pencil. Shelf spacing from bottom is 300mm each for 6 shelves (total 1800mm used), or adjust spacing at top for display shelves as per your design. Align two boards perfectly and mark simultaneously for shelf positions.

   Mark a line

   Use a try square

   MarkSTEP 5 / 20

   Tip

   • Clamping the two side boards together before marking ensures shelves align exactly on both sides.
   • Use typical book heights like A4(297mm), A5(210mm), and bunkobon size(150mm) to decide shelf spacing for convenient storage.

   Watch out

   • Misaligned shelf marks cause shelves to tilt. Mark both boards together clamped.
   • Forget to account for 19mm shelf thickness when calculating spacing results in too narrow actual shelf space.
6. 6

   Prepare Pilot Holes

   ≈ 20 min

   Drill 3mm diameter pilot holes at marked positions. Drill from outside of side boards toward the shelf ends, so the pilot hole penetrates side boards from outside to inside. Use masking tape on drill bit as a depth marker aiming for total depth of 29mm (19mm side board thickness plus 10mm into shelf board).

   Drill a hole

   下穴 φ3.5mm

   DrillSTEP 6 / 20

   Tip

   • 3mm pilot hole is 70% of coarse-thread screw shaft diameter (4.2mm), effectively preventing wood splitting.
   • Each shelf requires 2 pilot holes on each side board (4 per shelf), totaling 24 pilot holes for 6 shelves. Check not to miss any.

   Watch out

   • Insufficient depth means screws won't seat fully. Drill slightly deeper for safety.
   • Avoid drilling completely through the shelf board by using tape depth stop on drill bit.
7. 7

   Temporary Fix Shelves on One Side Board

   ≈ 20 min

   Lay one side board flat on the floor, stand 6 shelf boards vertically at marked positions. Temporarily fix with F-clamps and check right angles between side board and shelf boards using carpenter's square. Where square can't fit, check visually.

   Build the frame

   Check for square

   AssembleSTEP 7 / 20

   Tip

   • Start installing shelves from bottom up for stability.
   • One clamp per shelf board recommended; having 6 clamps eases work. If only 2 clamps available, proceed sequentially.

   Watch out

   • Fixing with incorrect right angles results in parallelogram distortion. Always confirm with carpenter's square.
   • Shelf boards protruding beyond side board edges prevents back panel installation.
8. 8

   Screw Shelves to One Side Board

   ≈ 15 min

   Drive coarse-thread screws 38mm through pilot holes from outside side board into shelf boards. Use 2 screws per shelf per position, 12 screws total for 6 shelves. Screw heads should be flush or countersunk 0.5mm below side board surface. Use medium torque on impact driver; finish tightening by hand with a quarter turn.

   Drive screws

   コーススレッド 51mm

   ScrewSTEP 8 / 20

   Tip

   • Slightly offset two screws vertically per position to increase withdrawal strength.
   • If screw holes are visible, optionally fill with wood dowels later.

   Watch out

   • Over-tightening screws in 19mm SPF lumber causes splitting. Use medium torque.
   • Screws driven at angle can protrude; remove, fill hole with wood filler, then re-screw in a corrected position.
9. 9

   Prepare to Attach Opposite Side Board

   ≈ 15 min

   Stand the sideboard with shelves fixed and hold the other side board on opposite shelf ends aligning with pencil marks. Temporarily fix with clamps. Check right angles while bookshelf is upright.

   Build the frame

   Check for square

   AssembleSTEP 9 / 20

   Tip

   • Two people recommended for this step: one supports bookshelf, another clamps.
   • Opposite side board marked at start; do not re-mark.

   Watch out

   • Attempting alone risks shelves falling off and dropping. Always work with two people or lean against a wall.
10. 10

    Screw Opposite Side Board

    ≈ 15 min

    Drive coarse-thread screws 38mm from outside opposite side board using pilot holes. Use 2 screws per position, 12 screws total. This completes fixing of both side boards and six shelf boards, forming the bookshelf’s main structure.

    Drive screws

    コーススレッド 51mm

    ScrewSTEP 10 / 20

    Tip

    • After securing both sides, check each shelf with a level for horizontality. Loosen and adjust if any shelf is tilted.

    Watch out

    • Driving screws simultaneously on both sides can warp the frame. Complete screwing one side fully before the other.
11. 11

    Check Overall Level and Diagonals

    ≈ 15 min

    Place assembled bookshelf on floor. Use a level to verify each shelf is horizontal. From front, measure diagonal distances (top-left to bottom-right and top-right to bottom-left) using measuring tape. Confirm the difference between these diagonals is within 5mm. If warped, loosen clamps to adjust and add screws to fix.

    Check level

    Level ✓

    LevelSTEP 11 / 20

    Tip

    • Diagonal difference over 5mm indicates parallelogram distortion. Correct before installing back panel.
    • Back panel increases rigidity. Correct distortions before back panel installation.

    Watch out

    • Shelves sagging in center worsens under book weight. Shelf length 600mm is acceptable; lengths over 1000mm need reinforcement consideration.
12. 12

    Prepare to Attach Back Panel

    ≈ 10 min

    Place the 4mm plywood back panel (1500×800mm) against bookshelf back. Align four corners and confirm diagonals match bookshelf to perform final distortion correction via back panel. Lightly fix back panel to bookshelf with masking tape once positioned.

    Build the frame

    Check for square

    AssembleSTEP 12 / 20

    Tip

    • Back panel is a key component to prevent distortion. Attaching it slightly skewed reduces rigidity.
    • The thin 4mm plywood can be held with staples for easy fixing. Drill pilot holes if using fine nails.

    Watch out

    • If back panel is larger than bookshelf, trim excess parts. If smaller, maintain even gaps within 5mm around edges.
13. 13

    Staple Back Panel

    ≈ 20 min

    Use a stapler (with about 15mm staples) or fine nails to fix back panel to side boards and shelf boards. Space staples about every 100-150mm, including along all edges and at shelf board positions. Start at corners, then work along diagonals sequentially to minimize distortion.

    Drive screws

    コーススレッド 51mm

    ScrewSTEP 13 / 20

    Tip

    • Stapler costs 1500-2500 yen at home center and is faster than nails. Worth the investment when making bookshelf.
    • Mark shelf positions on back panel with pencil to avoid missing attaching at shelf locations.

    Watch out

    • Staples protruding inside bookshelf risk book damage. 15mm staples are appropriate for 19mm thickness.
    • Only fixing back panel edges and shelf locations prevents panel sagging.
14. 14

    Prepare to Attach L-shaped Brackets

    ≈ 15 min

    Attach four 50mm L-shaped brackets: two on each side at upper rear edges of bookshelf. One side of bracket fixed to bookshelf top edge, the other side intended for wall fixing. Use a stud finder to locate wall studs for bracket placement.

    Fix to the wall

    Anchor to studs

    Wall mountSTEP 14 / 20

    Tip

    • Inexpensive stud finders from 100-yen shops are less accurate. Better to use ones from home center (1000-2000 yen).
    • Studs are usually spaced every 455mm. Once you find one, you can estimate positions of adjacent studs.

    Watch out

    • If wall is only gypsum board with no stud contact, screws won't hold, rendering tip-over prevention ineffective.
    • If bracket position and stud do not align, shift bracket horizontally to mount screw centrally on stud.
15. 15

    Attach L-shaped Brackets to Bookshelf

    ≈ 10 min

    Fix the four L-shaped brackets to side boards at bookshelf upper back outside with coarse-thread screws 38mm through bracket holes. Attach brackets flush with or within 5mm of side board surface, ensuring brackets protrude perpendicularly to wall side.

    Drive screws

    コーススレッド 51mm

    ScrewSTEP 15 / 20

    Tip

    • Ensure bracket bend faces wall and screw holes face bookshelf.
    • Use a level to verify brackets are not crooked.

    Watch out

    • Crooked brackets cause gaps between bracket and wall during fixing.
16. 16

    Set Bookshelf and Attach to Wall

    ≈ 20 min

    With two people, move bookshelf to installation location and stand it up. Push it tightly against the wall. Insert coarse-thread screws 45-50mm long (included or purchased) from wall side through L-shaped bracket holes into studs. Secure all four positions to complete tip-over prevention.

    Fix to the wall

    Anchor to studs

    Wall mountSTEP 16 / 20

    Tip

    • Use 45-50mm screws for wall side since 38mm screws are too short.
    • Wall fixing is the most important step to prevent injury or fatal accidents from quake-related tipping. Do not skip.

    Watch out

    • Drywall anchors alone do not provide sufficient strength; always screw into studs.
    • If gap between wall and bookshelf is over 5mm, insert shims before fastening. Leaving gap reduces bracket effectiveness.
17. 17

    Clean Before Painting

    ≈ 10 min

    Thoroughly vacuum and wipe entire bookshelf with a dry cloth to remove sawdust, oil, and fingerprints. Quality cleaning before painting greatly affects the finish. Plywood back panel absorbs paint quickly; optionally mask it before painting.

    Inspect

    No wobble ✓

    InspectSTEP 17 / 20

    Tip

    • Cleaning before painting should proceed in three steps: dry wipe, damp wipe, then dry wipe again for perfect cleanliness.

    Watch out

    • Remaining sawdust causes rough paint surface. Shine light on surface to check.
18. 18

    Apply First Coat of Oil Stain

    ≈ 40 min

    Apply oil stain (e.g. Watco Oil or Kinura) with a brush to all surfaces in order: outside side boards, shelf board tops, shelf board undersides, and back panel. After 10-15 minutes, wipe off excess with dry cloth. First coat uses about 60-70% of total oil amount due to absorption.

    Paint

    Watco oil / varnish

    PaintSTEP 18 / 20

    Tip

    • Oil stain application procedure: apply, wait 10-15 minutes, then wipe off excess.
    • Use 30-50mm wide brush optimal for bookshelf work; larger brushes miss detail areas.

    Watch out

    • Not wiping off excess leaves stickiness for over a week.
    • Plywood back panel absorbs oil quickly causing uneven color. Apply thinly and wipe carefully.
19. 19

    Apply Second Coat of Oil Stain

    ≈ 25 min

    After first coat dries 24 hours, apply second coat with 1/3 to 1/2 the amount of the first. Wipe off excess as before. Two coats deepen color and improve protection. Allow 24-48 hours for full drying.

    Paint

    Watco oil / varnish

    PaintSTEP 19 / 20

    Tip

    • Second coat corrects color unevenness from first coat. Apply evenly thin.
    • Add a third coat for darker color if desired.

    Watch out

    • Do not forget wiping off on second coat; thick application causes unevenness.
    • During drying, keep indoors free of dust and insects.
20. 20

    Completion, Start Usage, and Inspection

    ≈ 15 min

    After oil fully dries for 48 hours, place books and begin use. Load heaviest books on bottom shelves and lighter books on top for balance and stability. After one week of use, recheck screw tightness and L-bracket fixation, retightening as needed.

    Done!

    Done — nice work!

    DoneSTEP 20 / 20

    Tip

    • Place heavy books such as encyclopedias on bottom two shelves. Use light paperbacks on upper shelves.
    • Reapply oil every 3-5 years to renew gloss and protection.

    Watch out

    • Placing books immediately after finishing risks oil transferring to books. Always wait 48 hours or more for drying.
    • Books absorb moisture; use dehumidifiers in rainy seasons. Bookshelf may warp due to humidity.

Warnings

• ⚠️Drill pilot holes before driving screws to prevent wood splitting.

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