Engawa Deck

Dimensions

Cut list

Tools you'll need

• ✓

  Measuring tape (5m or longer)

  Used for measuring each component

• ✓

  Pencil and carpenter's square

  For marking lines and checking right angles

• ✓

  Saw

  Using home center cut service is recommended

• ✓

  Electric screwdriver

  Impact driver improves work efficiency

• ✓

  Sandpaper

  Prepare both #120 and #240 grit

• ✓

  Level

  Essential to verify levelness during assembly

• ✓

  Clamps (2 or more)

  Used for temporary fixing when joining parts

• ✓

  Brush and paint tray

  Used to apply wood preservative coating

• ✓

  Mason's line and stakes

  Used to set reference lines

• ✓

  Shovel and crushed stone

  Used for ground preparation and laying crushed stone

Materials

Build steps

1. 1

   Confirm placement location and check ground condition

   ≈ 30 min

   Measure the installation site for the Engawa Deck (veranda deck) sized 1800×600×350mm. Check ground levelness, sunlight exposure, ground strength (whether it is prone to becoming muddy), and water drainage paths.

   Measure

   W 1800 mm

   MeasureSTEP 1 / 10

   Tip

   • If the ground is soft, base foundation work is required. Lay crushed gravel thicker.
   • Maintain height (350mm) for ventilation under the deck. This prevents moisture buildup.
   • Confirm direction of rainwater flow and arrange so water doesn’t pool.

   Watch out

   • If ground is weak, the deck may settle and tilt over time.
   • Placing where water pools causes accelerated wood decay.
2. 2

   Prepare parts for cutting

   ≈ 30 min

   Prepare 18 decking boards of Western Red Cedar (20×90×600mm), 3 joists of 2×4 lumber (38×89×600mm), 3 beams of 4×4 lumber (89×89×1800mm). Prepare six 150mm square foundation stones and 108 stainless steel 90mm coarse-thread screws.

   Cut

   Use the in-store cut service

   CutSTEP 2 / 10

   Tip

   • Western Red Cedar has high water resistance; a standard outdoor decking material.
   • Selecting wood with fewer knots yields a beautiful finish; although more costly, it lasts longer.
   • Stainless steel screws are mandatory outdoors. Iron screws rust and stain wood black.

   Watch out

   • Using SPF lumber as substitute causes decay within 3-5 years; decking boards should be water-resistant species (Western Red Cedar, Ipe, etc.).
   • Insufficient screw length results in poor joist-to-beam connection.
3. 3

   Install foundation stones and ensure levelness

   ≈ 60 min

   Place foundation stones (150mm square) at the four corners of the site. Dig into the ground to embed them. Use mason's line and level to ensure the top surfaces of the four stones are level. Measure and align distances between stones (approximately 450mm left-right and front-back).

   Build the frame

   Tighten joints firmly

   AssembleSTEP 3 / 10

   Tip

   • Leveling foundation stones is the most important process and determines overall levelness. Take time with this step.
   • Stretching mason's line allows simultaneous confirmation of the four points' levelness.
   • Setting foundation stones slightly above ground improves drainage.

   Watch out

   • Uneven foundation stones cause the whole deck to tilt, objects placed on top may roll off.
   • Placing foundation stones where water pools causes water to rise into the wood.
4. 4

   Sand beams and joists

   ≈ 30 min

   Sand the 4×4 beams and 2×4 joists with #120 followed by #240 grit sandpaper. Since for outdoor use, preparing the surface before painting is critical. Pay special attention to end grain, as it is a primary water entry point.

   Sand

   #120

   SandSTEP 4 / 10

   Tip

   • Beams carry the heaviest load. Place surfaces without knots or cracks on top.
   • Joists are laid perpendicular to beams. Both components must be level.
   • Work outdoors to avoid dust; wear a mask.

   Watch out

   • Insufficient sanding prevents paint absorption, leading to early degradation.
   • Leaving sanding dust causes paint unevenness.
5. 5

   Apply first coating of preservative to beams and joists

   ≈ 60 min

   Before assembly, paint only the beams and joists. Apply wood preservative suitable for outdoor use (e.g., Xyladecor) on all surfaces, including joints that cannot be painted after assembly. Allow 24 hours drying.

   Paint

   Watco oil / varnish

   PaintSTEP 5 / 10

   Tip

   • Pre-painting joints significantly improves protective performance after assembly.
   • Apply extra preservative to end grain.
   • Components closer to the ground face higher decay risk; prioritize thorough coating in this order.

   Watch out

   • Assembling without pre-painting leaves joints uncoated and susceptible to water intrusion and rot.
   • If rain exposure occurs before drying, the coating may wash away. Check weather before application.
6. 6

   Attach beams

   ≈ 45 min

   Place three 4×4 beams (89×89×1800mm) parallel atop the foundation stones at intervals of 450mm. Insert a waterproof sheet between the foundation stones and beams to prevent capillary water rise. Secure beams from below using stainless steel screws or specialized metal connectors. Use a level to confirm levelness at all four points.

   Build the frame

   Tighten joints firmly

   AssembleSTEP 6 / 10

   Tip

   • Insert waterproof sheet (rubber sheet acceptable) between foundation stones and beams to prevent upward water movement by capillary action.
   • Using foundation stone hardware connectors strengthens joints. These are available at home centers.
   • Align beam lengthwise direction with water flow direction.

   Watch out

   • Omitting waterproof sheet allows water rise causing beam rot.
   • Uneven beams cause the entire structure to tilt.
7. 7

   Install joists

   ≈ 45 min

   Place three 2×4 joists (38×89×600mm) perpendicular on two of the beams at 350mm spacing. Drill 5mm pilot holes through joists into beams; fasten with two 90mm stainless steel coarse-thread screws per joint (total of 8 screws).

   Build the frame

   Tighten joints firmly

   AssembleSTEP 7 / 10

   Tip

   • 350mm joist spacing is standard span to support 20mm thick decking boards; wider spacing causes board sagging.
   • Pilot holes prevent wood splitting, especially important for relatively brittle 4×4 lumber.
   • Confirm joist top surfaces are level during fastening.

   Watch out

   • Joist spacing greater than 500mm causes decking boards to sag under weight.
   • Insufficient screw length fails to reach beam, weakening strength.
8. 8

   Attach decking boards

   ≈ 60 min

   Arrange 18 Western Red Cedar decking boards (20×90×600mm) perpendicular to joists. Insert 5mm spacers (thickness of one nail) between boards to maintain consistent gaps for drainage and ventilation. Drill 3mm pilot holes at joist intersections and fasten with two 50mm stainless steel screws per board (total 18 screws).

   Build the frame

   Tighten joints firmly

   AssembleSTEP 8 / 10

   Tip

   • 5mm gaps prevent water accumulation and allow ventilation; do not omit.
   • Use 5mm thick spacers for consistent gaps.
   • Fix boards with concave side downward (toward joists) considering board warping; upward warp causes discomfort when walking.

   Watch out

   • Omitting gaps causes water pooling and rot on board undersides.
   • Driving screws too close to board edges causes edge splitting.
9. 9

   Sand and coat decking boards

   ≈ 90 min

   Sand all decking boards with #120 then #240 grit sandpaper, thoroughly sanding board surfaces, edges, and end grains. Remove sanding dust before applying two coats of outdoor wood preservative paint. Allow 24 hours drying between coats.

   Paint

   Watco oil / varnish

   PaintSTEP 9 / 10

   Tip

   • Sanding opens wood pores allowing better paint absorption.
   • Apply extra preservative on end grain.
   • Use stainless steel screws; iron screws rust within one year.

   Watch out

   • Missed coating spots allow water penetration and rot; paint carefully.
   • Rain before drying causes coating to run off; check weather forecast before painting.
10. 10

    Final checks and maintenance planning

    ≈ 30 min

    Inspect entire deck. Check screw tightness, board levelness, gap uniformity, and coating consistency. Test drainage by sprinkling water. Do not place heavy objects on first day to allow coating to fully cure. Annual recoating extends deck lifespan beyond 10 years.

    Done!

    Done — nice work!

    DoneSTEP 10 / 10

    Tip

    • Lightly sand with #240 grit once a year before recoating extends lifespan beyond 10 years.
    • Monthly removal of leaves and soil under deck prevents moisture buildup.
    • In cold regions, painting before winter maintains protection through spring.

    Watch out

    • Neglecting maintenance outdoors causes coating to peel and decay within 2-3 years; annual repainting is key to longevity.
    • Leaving moisture sources such as leaves and soil accumulation under deck causes underside rot.

Warnings

• ⚠️If used outdoors, wood preservative coating is essential (reapply annually recommended).
• ⚠️Use stainless steel screws (iron screws will rust).
• ⚠️Drill pilot holes before screwing to prevent wood splitting.
• ⚠️Install foundation stones level (uneven placement will warp the joists).

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