How to Build a Small Ground-Level Deck: A Measured DIY Plan

THE SHORT ANSWER

A small ground-level deck is safest to plan as a freestanding, low platform that is drained, ventilated and kept separate from the house until local requirements and the actual support system are checked. The worked example is about 2,400 × 1,818 mm using 19 deck boards, a 90 × 45 mm timber frame and a 6 mm board gap; treat those dimensions as a layout example, not a structural design or permission to build over unsuitable ground.

Regional note

This guide is written for South Africa, Australia, New Zealand. Always check local codes, product specifications, licences, and site conditions.

Preparation

Check the ground, exposure and rules before cutting timber

A deck fails at the site and support details long before a board colour becomes the problem. Confirm the ground, drainage, finished levels and local requirements before ordering material.

Measure the finished rectangle, door thresholds, steps, boundaries, windows and service routes. Mark the 2,400 × 1,818 mm example on the ground so the real circulation and door swing can be checked.
Check whether the ground floods, holds water, contains roots or unstable fill, or slopes toward the house. A deck is not a drainage fix: keep water moving away from walls and preserve inspection access.
Confirm local planning, building-control, sectional-title, strata, body-corporate, boundary, pool, balustrade, bushfire and electrical requirements before construction. Requirements vary by location, height, attachment and site risk.
Choose boards, treated timber, coatings and fasteners as one compatible system. Coastal salt, pool splash, high UV, wet ground and bushfire exposure can change the suitable product and maintenance plan.
Check the actual dressed size, straightness and moisture condition of every board and joist. Nominal timber sizes are not cutting dimensions; make a dry layout before final cuts.
Keep the deck freestanding in this example. Do not cut into the house, bridge a damp-proof course, cover weep holes or attach a ledger until a competent local person has confirmed the detail and approvals.

Decision guide

Worked-example cut list (millimetres)

This example lays 19 × 2,400 mm deck boards across a roughly 1,818 mm deep platform with 6 mm gaps. It is a material and layout worksheet, not a span table, footing design, balustrade design or structural approval.

Part	Quantity and cut	Material / check
Deck boards	19 × 2,400 × 90 nominal	Use the selected board system's actual width and required gap. Nineteen 90 mm boards with eighteen 6 mm gaps cover 1,818 mm before edge trimming.
Outer frame	2 × 2,400; 2 × 1,728	90 × 45 mm treated or otherwise suitable structural timber. The short sides fit between the long sides; confirm actual section size before cutting.
Internal cross-joists	5 × 1,728	90 × 45 mm timber. The example places them between the outer long sides at about 400 mm centres; verify the selected board and frame system's span and spacing limits.
Support and levelling	A layout of adjustable supports, pavers or bearers sized for the ground and system; quantity not universal	Do not copy a support count from this article. Use a drained, stable, site-appropriate support detail designed for the soil, load, height and local rules.
Edge and access	Optional fascia boards cut on site after the frame is level; steps, handrails and barriers only if required	Measure finished levels first. A barrier, stair, pool edge or retaining condition needs its own compliant design; it is not included in this low platform example.
Hardware	Corrosion-resistant screws or the board manufacturer's specified clips, plus compatible frame fixings and washers	Match the exposure and treated timber chemistry. Pre-drill near ends, keep fixings flush, and follow the complete product instructions.
Allowance	Add at least 10% board and timber allowance for defects, end cuts and layout changes	Do a real nesting layout before purchase. Offcuts are not automatically usable where grain, end distance or joint location matters.

The method

Step by step

Prove the footprint and finished level

Mark the 2,400 × 1,818 mm example with string, then place a chair, table and any access route inside the proposed rectangle. Check door thresholds, rainwater flow, window openings and the lowest surrounding ground. Set a finished level that sheds water away from the building without creating a trip edge or covering vents, damp-proof details or inspection points.

Prepare a stable, drained support zone

Remove organic material and loose debris, then form a stable, drained support arrangement suited to the site. Keep timber off soil and standing water. The number and type of supports depend on ground conditions, load, deck height, local rules and the selected system; obtain a competent design where the ground is filled, retaining, sloping, wet or uncertain.

Cut, label and dry-lay the frame

Cut two 2,400 mm outer sides, two 1,728 mm end joists and five 1,728 mm internal cross-joists only after checking the real timber size. Label every part, reject splits or twist that compromise a joint, and dry-lay the rectangle on the supports. Measure both diagonals and adjust until the frame is square before fixing.

Fix the frame and check the water path

Join the outer frame and cross-joists with the selected compatible fixings, keeping all joints supported and the top plane level. Recheck the support contact, underside ventilation, edge clearances and drainage route. Do not trap water against the house, seal over inspection access or rely on deck boards to correct a frame that is out of level.

Lay the boards with the selected gap

Dry-lay the 19 boards first, starting from the most visible edge and keeping the end lines consistent. Use the board manufacturer's gap, fixing and end-distance instructions rather than treating 6 mm as universal. Trim the final board or adjust the frame only after the actual width, moisture movement and edge detail have been checked.

Finish, inspect and plan maintenance

Ease sharp edges, remove splinters and set every fixing flush without crushing the board. Fit edge boards only after the platform is stable; keep ventilation and drainage open. Wash off construction dust as the product permits, allow coatings to cure fully, and inspect early for movement, ponding, corrosion, decay, loose fixings or trip edges.

Before you start

Expert tips

The 2,400 × 1,818 mm example is deliberately a layout exercise. Change the length, depth, board direction and frame spacing only after recalculating the full system from current product data.
Keep the deck low and freestanding while planning. Height, attachment, stairs, barriers, pool proximity and boundary conditions can move the project into a different approval or design category.
Near the coast or a pool, use fasteners and connectors specifically compatible with the timber treatment and exposure; ordinary bright screws can stain, corrode or fail prematurely.
Leave the underside inspectable. A neat fascia that blocks air, drainage or access can shorten the life of the deck and hide a problem until repair is expensive.
A deck is not a retaining wall, roof, scaffold, vehicle stand or foundation. Do not add a roof, spa, masonry wall, heavy planter or enclosed room without a new design and local checks.

Common questions

How much does it cost to build a small deck?+

There is no responsible universal price. Build a line-by-line take-off for boards, frame timber, supports, fixings, steps or barriers, delivery, waste, coatings, tools and any professional design or approval work. Ground preparation and access can cost more than the visible boards.

Can I build a deck directly on soil?+

Do not place deck timber directly on soil. Organic ground, retained moisture and uneven settlement can cause decay and movement. Use a stable, drained support system suited to the actual ground and keep the underside ventilated and inspectable.

How far apart should deck joists be?+

There is no universal spacing. Use the current span and spacing limits for the exact board, timber, load, support arrangement and exposure, then check local requirements. The approximately 400 mm example is a planning starting point, not a structural approval.

Should I attach a deck to my house?+

Do not attach it by copying a generic ledger detail. A connection can affect waterproofing, damp-proof courses, flashing, structure, movement, drainage and approvals. A competent local person should confirm the building and site detail before any attachment is made.

Do I need permission for a ground-level deck?+

Maybe. Rules vary with height, size, attachment, boundary, pool or barrier conditions, property title, bushfire exposure and local authority. Check the current requirements before buying material; low does not automatically mean exempt.

What is the best decking material for a wet or coastal site?+

Choose a complete system, not a board in isolation. Compare timber or composite exposure limits, drainage, ventilation, fixing compatibility, corrosion resistance, heat, slip, maintenance and replacement availability. A locally suitable product and sound support detail matter more than a generic 'best' label.

Primary references

Sources & further reading

We link to official building-code, government and public-health material where a technical or safety claim needs authoritative context. Local rules and adopted code editions can change.

Know your limit

Stop if the work involves structural uncertainty, hazardous materials, heights, live services, gas, serious water damage, or regulated work. Local rules differ—use an appropriately licensed professional where required.