Mini Wood Deck

Dimensions

Cut list

Tools you'll need

• ✓

  Measuring Tape (5m or longer)

  Used for measuring all parts.

• ✓

  Pencil and Carpenter's Square

  For marking lines and checking right angles.

• ✓

  Saw

  Using a home center's cutting service is recommended.

• ✓

  Electric Screwdriver

  Impact drivers improve work efficiency.

• ✓

  Sandpaper

  Prepare two types: #120 and #240 grit.

• ✓

  Level

  Essential for checking levelness during assembly.

• ✓

  Clamps (2 or more)

  Used for temporary holding during joining.

• ✓

  Brush and Paint Tray

  Used for applying wood preservative.

• ✓

  Chalk Line and Stakes

  Used to set reference lines.

• ✓

  Shovel and Crushed Stone

  Used for ground leveling and laying crushed stone.

Materials

Build steps

1. 1

   Confirm Installation Site and Check Ground Conditions

   ≈ 30 min

   Measure the installation area for the mini wood deck (900×900×300mm). Check the ground for levelness, sunlight exposure, soil strength (avoid soft or muddy areas), and drainage paths.

   Measure

   W 900 mm

   MeasureSTEP 1 / 10

   Tip

   • If the soil is soft, ground preparation is necessary. Lay gravel thickly.
   • Maintain the deck height at 300mm for good ventilation and moisture control.
   • Confirm the direction of water flow to avoid water pooling under the deck.

   Watch out

   • If the ground is weak, the deck may sink and tilt over time.
   • Placing the deck where water pools causes the wood to rot quickly.
2. 2

   Prepare Parts for Cutting

   ≈ 30 min

   Prepare 9 boards of Western Red Cedar deck material (20×90×900mm), 4 joists made from 2x4 lumber (38×89×900mm), and 2 beams made from 4x4 lumber (89×89×900mm). Also prepare 4 concrete deck blocks (150mm square) and 72 stainless steel 90mm coarse-thread screws.

   Cut

   Use the in-store cut service

   CutSTEP 2 / 10

   Tip

   • Western Red Cedar has high water resistance and is standard for outdoor decks.
   • Selecting boards with few knots results in a beautiful finish. Though more expensive, it ensures longer life.
   • Stainless steel screws are mandatory outdoors. Iron screws rust and stain wood black.

   Watch out

   • Substituting with SPF lumber leads to rotting within 3-5 years. Use water-resistant species like Red Cedar or Ipe.
   • Insufficient screw length results in poor beam-to-joist connection.
3. 3

   Set Concrete Deck Blocks and Level Them

   ≈ 60 min

   Place four concrete deck blocks (150mm square) at the installation area's corners. Dig the ground and embed them. Use chalk line and level to ensure all four deck block tops are level. Confirm distances between blocks (approx. 450mm left-right and front-back) by measurement.

   Build the frame

   Tighten joints firmly

   AssembleSTEP 3 / 10

   Tip

   • Setting deck blocks level is the most important step determining overall levelness. Spend ample time here.
   • Using chalk line allows simultaneous level checking at four points.
   • Installing blocks slightly higher than the ground improves drainage.

   Watch out

   • Uneven deck blocks cause the entire deck to tilt and objects placed on it to roll.
   • Installing deck blocks where water pools causes moisture to rise into the wood.
4. 4

   Sand Beams and Joists

   ≈ 30 min

   Sand the 4x4 beams and 2x4 joists from #120 to #240 grit. As these will be outdoors, preparing the surface well before finishing is crucial. Pay special attention to end grain, which is prone to water ingress.

   Sand

   #120

   SandSTEP 4 / 10

   Tip

   • Beams bear the most load; place knot-free and crack-free sides upwards.
   • Joists rest perpendicular on beams; both must have level surfaces.
   • Conduct sanding outdoors and wear a mask to avoid inhaling dust.

   Watch out

   • Insufficient sanding prevents finish penetration, leading to early deterioration.
   • Leaving sanding dust causes blotchy finish application.
5. 5

   Apply First Coat of Wood Preservative to Beams and Joists

   ≈ 60 min

   Before assembly, apply wood preservative to beams and joists. Coating junction surfaces beforehand ensures greater decay resistance after assembly. Use exterior wood preservative (e.g., Xyladecor) and allow 24 hours drying.

   Paint

   Watco oil / varnish

   PaintSTEP 5 / 10

   Tip

   • Coating junctions first significantly improves decay resistance after assembly.
   • Apply more preservative to end grain.
   • Treat parts closest to the ground most thoroughly due to higher decay risk.

   Watch out

   • Not coating prior to assembly leaves junctions unprotected, allowing water ingress and decay.
   • Applying preservative before forecasted rain risks wash-off; check weather before coating.
6. 6

   Attach Beams

   ≈ 45 min

   Place two beams (89×89×900mm) parallel on top of concrete deck blocks spaced 450mm apart. Insert a waterproof sheet between the beam and block. Secure beams to blocks from below with stainless steel screws or dedicated brackets. Check level at all four points with a level.

   Build the frame

   Tighten joints firmly

   AssembleSTEP 6 / 10

   Tip

   • Insert waterproof sheet (rubber sheet is acceptable) between deck block and beam to prevent capillary water rise.
   • Using deck block brackets strengthens connections; available at home centers.
   • Align beam lengths with the water flow direction.

   Watch out

   • Omitting waterproof sheet allows water rise and beam decay.
   • If beams are not level, the entire deck will be tilted.
7. 7

   Attach Joists

   ≈ 45 min

   Place four joists (38×89×900mm) perpendicular on the two beams, spaced at 300mm intervals. Drill 5mm pilot holes through the beams and drive two 90mm stainless steel coarse-thread screws per joist-beam joint (total 8 screws).

   Build the frame

   Tighten joints firmly

   AssembleSTEP 7 / 10

   Tip

   • 300mm joist spacing supports 20mm thick deck boards adequately; wider spacing causes board sagging.
   • Drilling pilot holes prevents wood splitting, especially as 4x4 lumber, while thick, splits easily.
   • Check the joist top surfaces are level during fixing.

   Watch out

   • If joists are spaced beyond 500mm, deck boards will sag under weight.
   • Insufficient screw length prevents reaching beams, resulting in weak joints.
8. 8

   Attach Deck Boards

   ≈ 60 min

   Lay nine Western Red Cedar deck boards (20×90×900mm) perpendicular to joists. Maintain a 5mm gap between boards using 5mm thick spacers (equal to the thickness of one nail). Drill 3mm pilot holes and fix each board with two 50mm stainless steel screws into joists (total 18 screws).

   Build the frame

   Tighten joints firmly

   AssembleSTEP 8 / 10

   Tip

   • 5mm gaps are essential for water drainage and ventilation; closing gaps causes water pooling.
   • Using 5mm spacers ensures even gaps.
   • When securing boards, orient concave side down (toward joists) considering board warping. Convex side up feels unpleasant when walking.

   Watch out

   • Omitting deck board gaps causes water pooling and underside rot.
   • Driving screws too close to board edges causes splitting.
9. 9

   Sand and Apply Wood Preservative to Deck Boards

   ≈ 90 min

   Sand all deck boards from #120 to #240 grit, including surfaces, edges, and end grain. Remove sanding dust thoroughly, then apply two coats of exterior wood preservative. Allow 24 hours drying between coats.

   Paint

   Watco oil / varnish

   PaintSTEP 9 / 10

   Tip

   • Sanding opens wood pores, allowing better finish penetration.
   • Apply extra preservative to end grain.
   • Choose stainless steel tools; iron tools rust within a year.

   Watch out

   • Incomplete coverage allows water ingress causing rot; apply carefully.
   • Coating before full drying and rain will cause finish to wash away; check weather forecast.
10. 10

    Final Check and Maintenance Plan

    ≈ 30 min

    Inspect overall structure. Check screws are tight, boards are level, gaps uniform, and finish is even. Test drainage by pouring water. Avoid placing heavy objects for initial coating cure. Annual refinishing extends deck lifespan beyond 10 years.

    Done!

    Done — nice work!

    DoneSTEP 10 / 10

    Tip

    • Lightly sand with #240 grit and reapply finish yearly to extend life over 10 years.
    • Remove leaves and mud under deck monthly to remove humidity source.
    • In cold regions, apply finish before winter to protect until spring.

    Watch out

    • Neglecting maintenance leads to finish peeling and rot in 2-3 years; annual recoating is critical.
    • Leaving humidity sources like leaves and soil under deck causes rot from below.

Warnings

• ⚠️When used outdoors, applying a wood preservative is essential (annual reapplication recommended).
• ⚠️Use stainless steel screws (iron screws will rust).
• ⚠️Drill pilot holes before screwing to prevent wood splitting.
• ⚠️Install concrete deck blocks on a level surface (if tilted, joists will warp).

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