Balcony Wood Deck

Dimensions

Cut list

Tools you'll need

• ✓

  Measuring Tape (5m or longer)

  Used for measuring each part

• ✓

  Pencil and Carpenter's Square

  Used for marking lines and confirming right angles

• ✓

  Saw

  Recommended to use home center cutting service

• ✓

  Electric Driver

  Impact driver improves work efficiency

• ✓

  Sandpaper

  Prepare #120 and #240 grit

• ✓

  Level

  Essential for checking level during assembly

• ✓

  Clamps (2 or more)

  Used for temporary fixing during joining

• ✓

  Brush and Paint Tray

  Used for applying wood preservative

• ✓

  Chalk Line and Stakes

  Used for setting reference lines

• ✓

  Shovel and Crushed Stone

  Used for ground leveling and crushed stone laying

Materials

Build steps

1. 1

   Confirm Installation Location and Ground Check

   ≈ 30 min

   Measure the installation area for the balcony wood deck (1800×1200×150mm). Check ground level, sunlight exposure, ground strength (whether it is prone to muddiness), and drainage paths.

   Measure

   W 1800 mm

   MeasureSTEP 1 / 10

   Tip

   • If the ground is soft, ground preparation is necessary. Lay crushed stone thickly
   • Ensure the deck height allows ventilation underneath (150mm). Moisture prevention
   • Confirm the direction of rainwater flow and arrange so that water does not accumulate

   Watch out

   • If the ground is weak, the deck may settle and tilt over time
   • Water accumulation spots cause premature wood decay
2. 2

   Prepare Materials for Cutting

   ≈ 30 min

   Prepare 18 pieces of Western Red Cedar deck boards (20×90×1200mm), 4 pieces of 2x4 lumber joists (38×89×1200mm), and 3 pieces of 4x4 lumber beams (89×89×1800mm). Also prepare six foundation stones (150mm square) and 144 pieces of 90mm stainless coarse-thread screws.

   Cut

   Use the in-store cut service

   CutSTEP 2 / 10

   Tip

   • Red cedar is highly water-resistant and a standard material for outdoor decks
   • Select boards with few knots for a beautiful finish. It may be more expensive but lasts longer
   • Stainless screws are essential outdoors. Iron screws rust and stain the wood black

   Watch out

   • Using SPF lumber as a substitute causes decay within 3-5 years. Use water-resistant species (e.g., red cedar, ipe) for deck boards
   • If screw length is insufficient, joists and beams will not be firmly joined
3. 3

   Install Foundation Stones and Leveling

   ≈ 60 min

   Place foundation stones (150mm square) at the four corners of the installation area. Dig into the ground and embed the foundation stones. Use chalk line and level to align the top surfaces of all four stones horizontally. Measure and unify the distances between stones (approx. 450mm left-right and 450mm front-back).

   Build the frame

   Tighten joints firmly

   AssembleSTEP 3 / 10

   Tip

   • Leveling foundation stones is the most critical step affecting overall level; take your time
   • Using a chalk line helps confirm horizontal level of all four points simultaneously
   • Install foundation stones slightly elevated from the ground to improve drainage

   Watch out

   • If foundation stones are uneven, the entire deck will tilt and objects may roll off
   • Placing foundation stones where water collects causes water to rise and damage wood
4. 4

   Sanding Beams and Joists

   ≈ 30 min

   Sand the 4x4 lumber beams and 2x4 lumber joists with #120 and then #240 grit sandpaper. Surface preparation before coating is important for outdoor use. Pay particular attention to end grain as it attracts water.

   Sand

   #120

   SandSTEP 4 / 10

   Tip

   • Beams carry the heaviest loads; place faces without knots or cracks facing upward
   • Joists rest perpendicularly on beams; a level surface is vital for both
   • Perform sanding outdoors and wear a dust mask

   Watch out

   • Insufficient sanding prevents paint penetration and leads to early deterioration
   • Leftover sanding dust causes uneven paint application
5. 5

   Apply First Coat of Preservative to Beams and Joists

   ≈ 60 min

   Before assembly, coat only the beams and joists. The trick is to paint surfaces that will be inaccessible after assembly first. Apply outdoor wood preservative (e.g., Xyladecor) thoroughly and allow 24 hours to dry.

   Paint

   Watco oil / varnish

   PaintSTEP 5 / 10

   Tip

   • Pre-coating joining surfaces greatly improves preservation after assembly
   • Apply extra preservative to end grain
   • Prioritize coating for parts closest to the ground where decay risk is higher

   Watch out

   • If you assemble first without coating, joints remain uncoated allowing water ingress and decay
   • Do not paint if rain is expected before drying; paint film will wash away. Check weather forecast
6. 6

   Attach Beams

   ≈ 45 min

   Place three 89×89×1800mm beams parallel on the foundation stones spaced approx. 450mm apart. Insert a waterproof sheet between the foundation stone and beam joint. Fix using stainless screws or dedicated hardware from below. Check horizontal level at all four points with a level.

   Build the frame

   Tighten joints firmly

   AssembleSTEP 6 / 10

   Tip

   • Insert waterproof sheet (rubber sheet also acceptable) between foundation stones and beams to prevent water capillary rise
   • Special foundation stone hardware strengthens joints; available at home centers
   • Align beam lengthwise direction with direction of water flow

   Watch out

   • Omitting waterproof sheet allows water to rise and rot beams
   • If beams are not level, the entire deck will tilt
7. 7

   Attach Joists

   ≈ 45 min

   Place four 38×89×1200mm joists perpendicularly on two beams at 150mm intervals. Drill 5mm pilot holes from above into joists, then drive two 90mm stainless coarse-thread screws per joint (total 8 screws).

   Build the frame

   Tighten joints firmly

   AssembleSTEP 7 / 10

   Tip

   • Standard support span for 20mm thick deck boards is 300mm; wider spacing causes sagging
   • Pilot holes prevent wood splitting; 4x4 lumber, though thick, splits easily
   • Confirm and maintain joist top surface level during fastening

   Watch out

   • Joist spacing over 500mm causes deck boards to sag under weight
   • Insufficient screw length fails to reach beams, leading to weak joints
8. 8

   Attach Deck Boards

   ≈ 60 min

   Arrange 18 pieces of 20×90×1200mm red cedar deck boards perpendicular to joists. To create 5mm gaps between boards, insert 5mm thick spacers (thickness of one nail) while fastening. Drill 3mm pilot holes at joist joints and drive two 50mm stainless screws per board (total 36 screws).

   Build the frame

   Tighten joints firmly

   AssembleSTEP 8 / 10

   Tip

   • 5mm gaps are essential for water drainage and ventilation; close gaps cause water pooling
   • Use 5mm spacers to maintain uniform gaps
   • Fix boards with concave side facing downwards (toward joists) considering board warping; convex side on top feels uncomfortable when walking

   Watch out

   • Omitting gaps causes water pooling and underside decay
   • Driving screws too close to edges causes end splits
9. 9

   Sand and Paint Deck Boards

   ≈ 90 min

   Sand all deck boards with #120 then #240 grit sandpaper, carefully sanding surfaces, edges, and end grain. Remove sanding dust thoroughly. Apply outdoor wood preservative twice, allowing 24 hours drying between coats (1st coat → 24h dry → 2nd coat → 24h dry).

   Paint

   Watco oil / varnish

   PaintSTEP 9 / 10

   Tip

   • Sanding opens wood pores for better paint absorption
   • Apply extra preservative to end grain
   • Always choose stainless steel screws; iron screws rust within a year

   Watch out

   • Areas missed with preservative allow water infiltration and decay; paint carefully
   • If exposed to rain before drying, paint film will wash off. Check weather forecast before painting
10. 10

    Final Inspection and Maintenance Planning

    ≈ 30 min

    Inspect the whole structure. Check screw tightness, board levelness, gap uniformity, and coating evenness. Pour water to check drainage. Do not place heavy objects on the first day to allow full paint curing. Annual repainting maintains deck life over 10 years.

    Done!

    Done — nice work!

    DoneSTEP 10 / 10

    Tip

    • Lightly sand with #240 grit once a year then repaint with the same preservative, extending lifespan beyond 10 years
    • Monthly removal of leaves and mud under the deck cuts moisture sources
    • In cold climates, repaint before winter to maintain protection through spring

    Watch out

    • Outdoor neglect causes paint to peel and decay starts within 2-3 years; annual repainting is key to longevity
    • Leaving moisture sources like leaves and soil accumulation under the deck causes decay from below

Warnings

• ⚠️Wood preservative coating is essential for outdoor use (recoating recommended once a year)
• ⚠️Use stainless steel screws (iron screws will rust)
• ⚠️Pre-drill pilot holes before screwing to prevent wood splitting
• ⚠️Install foundation stones level (uneven placement will warp the joists)

Find more blueprints in this category or store