Building a wooden garden deck: terrace step by step

Why a wooden deck?

A wooden deck (garden terrace) brings character and warmth to your garden. Unlike concrete, wood feels alive and makes your front yard look natural. A well-built deck lasts 20-30 years and maintenance is simple.

However: a poorly built deck falls apart in five years due to rotted beams, mould and settling. The secret lies in preparation: good woodwork and a solid substructure determine your success.

Choosing wood

Not all wood works outdoors. You need wood that withstands moisture and weather.

Treated hardwood (Cumaru, Ipe): Very durable (25-30 years), dark, beautiful, expensive (40-80 euros per square metre). Best for longevity.

Treated pine: Affordable (10-20 euros per square metre), lasts 8-12 years, needs regular oiling. Good for budget.

Tropical hardwoods (Bangkirai): Mid-range price, durable (15-20 years), nice colour, greysening (normal, no problem).

For this guide we use treated pine - accessible and proven.

Substructure is your foundation

This is where many fail. They build a nice deck and forget the posts. Your deck sinks because posts rot or settle.

You need:

• Concrete posts or treated wooden posts: At intervals of 1-1.5 metres under your deck beams
• Height: Posts kept out of wet (minimum 30 cm above ground)
• Level: All posts at the same height (use a level)

Never set posts in wet grass - bury them in concrete.

Materials (for roughly 12 square metres of deck)

• Treated beams (5x20 or 6x20 cm) for substructure: roughly 80 metres
• Treated boards (2x15 cm) for decking: roughly 48 square metres
• Stainless steel screws (5 cm and 8 cm)
• Concrete posts (10x10 cm), minimum 60 cm long: roughly 8-10 units
• Concrete or ground screws for posts

Step-by-step

Step 1: Choose location and mark out

Determine where your deck goes. Mark the boundaries with chalk or twine. Measure and establish exact dimensions (length x width).

Check roughly with a level if the ground is even. Small slopes are okay - you correct with posts.

Step 2: Dig and place concrete posts

Dig holes for your concrete posts (roughly 1-1.5 metres apart). Posts must be at least 60 cm deep in ground, set in concrete. This prevents settling.

Watch the level carefully: all posts at the same height. Use a level. This is critical - poor posts equal wobbling deck.

Step 3: Lay support beams (substructure)

Once posts are set, lay beams across (perpendicular to your future boards). Screw them down with stainless steel screws (two per post).

Ensure your beams lie truly level. Check once more with level.

Step 4: Cross beams (length direction)

Lay a second row of beams perpendicular to your support beams (along your future board direction). These support your deck boards. Screw these too (two screws per intersection).

You now have a regular grid frame of beams under your deck.

Step 5: Keep spacing between boards (expansion)

For your deck boards: allow 3-5 mm gap between each board (wooden boards swell in damp weather and shrink in dry). Use a thin spacer while laying.

Step 6: First row of deck boards

Screw your first row of boards onto your substructure. Use two stainless steel screws per intersection (where board meets beam). Screws in the middle of the board, not at edges (prevent splitting).

Ensure your boards sit tightly - no wobbling.

Step 7: Next rows

Add board after board, always with spacer between. Watch that you do not over-tighten - wood can split.

Step 8: Edge finishing

At the edges of your deck you can place decorative edge boards (angle-cut for neater appearance). This gives your deck a finished look.

Maintaining your deck

• Year 1-2: Wood greysens - normal. You can sand if you wish, but not necessary.
• Yearly: Check screws, tighten where needed. Remove leaves etc.
• Every couple years: Apply oil/stain (optional, for extra protection).

Frequently asked questions

How long does my deck last?

With treated pine: 8-12 years. Bangkirai: 15-20 years. Exotic hardwood: 25-30 years. Depends also on maintenance.

Can I lay my deck on ground without posts?

No. Wood against wet ground rots immediately. Posts keep wood away from ground. Essential.

How much slope can my ground have?

Small slopes okay (1:20 or less). Large slopes difficult - you must correct much height difference with posts. Better for flatter sites.

I hear creaking sounds in my deck - what is that?

Wood working (expansion/shrinking from weather). Normal. If your deck genuinely wobbles, check your screws - they may have loosened.

Can I paint my deck?

Yes, but better is oil or leave natural (greyish colour is nice and protective). Paint splits easily on decks.

A good deck is years of comfort

A wooden terrace gives your garden warmth and beauty. Not to be overlooked: strong foundation determines whether your deck lasts for years or degrades quickly.

On gardenworld.app you can place your deck in your garden design and see how terraces bring your front yard to life. Plan, design, build.

For wooden structures and garden terraces, gardenworld.app offers visualisation and planning.