I built a backyard wood deck — entirely DIY!
It was a much bigger project than the small furniture I’d made before, but the result was completely worth it: it’s genuinely useful day to day, and I love how it looks.
I originally built the whole thing with cost-friendly SPF lumber and outdoor stain. After five years, the deck boards started showing their age, so I eventually replaced them with hardwood.
How a Wood Deck is Built — The Basics
Basic structure and terminology
A wood deck has a pretty consistent structure (see diagram below).
You start by deciding the floor footprint, then design the structural elements — concrete footings, support posts, and joists — to match.
For this build, I used 2x lumber for everything:
Decking boards: 2×4 — actual size 1½″ × 3½″ (38 × 89 mm)
Joists: 2×6 — actual size 1½″ × 5½″ (38 × 140 mm)
Support posts: 4×4 — actual size 3½″ × 3½″ (89 × 89 mm)
→ See “Materials” below for more on the lumber.
Planning
Deck size and height
I sized the deck at 6 ft wide × 4 ft deep (1,800 × 1,200 mm).
Honestly, I would have liked it bigger — but that’s about all the yard could spare.
For the deck height, I wanted it to flow nicely from the room, so I set the deck surface just below the sliding door track, as shown:
Post and joist spacing
The general rules of thumb for spacing are:
・Support post spacing: 24″–40″ (600–1,000 mm) → I used 40″ (1,000 mm)
・Joist spacing: 24″–32″ (600–800 mm) → I used 32″ (800 mm)
(If you’re building somewhere with a deck code — most of North America — check your local joist-spacing requirement first. 16″ on center is the usual baseline there, which is tighter than what I used here.)
For my deck size, I just barely managed to fit within the upper-end spacing limits, as shown:
Footings — using existing concrete
There was an existing concrete step (a traditional feature in Japanese homes called kutsunugi-ishi, basically a stone “shoe-removal step” right outside the sliding door) under the window where the deck would go. I just used that existing concrete as a footing for one side.
Materials
Lumber
I prioritized cost, workability, and availability — so all the lumber for this build was SPF.
Wood used in decks is typically classified as either softwood or hardwood. SPF is a softwood and isn’t well suited to outdoor use on its own, so when you build a deck with SPF, staining/sealing is essential.
| Pros | Cons | |
| Softwood (SPF, etc.) | ・Soft — easy to cut and screw ・Inexpensive | ・Lower durability — staining/sealing required |
| Hardwood (Ipe, Cumaru, etc.) | ・High durability (can be left unfinished) ・Less warping ・Better appearance | ・Hard — much trickier to work with (requires pre-drilling) ・Expensive |
Stain and painting supplies
For most of my DIY work, I stain or paint after assembly — that way I can skip the parts no one will ever see.
But on a deck, that doesn’t fly: once the structure is together, you can no longer reach the bottom of the joists or the inside of the post connections. So this time, I painted everything before assembly.
Stain
I used water-based Xyladecor — a classic exterior stain that’s widely used for decks.
Brushes and a tarp
Just regular paint brushes (see below).
I also laid down a tarp to keep stain drips off the ground while I worked.
Screws and footings
Screws
I used stainless steel coarse-thread deck screws. Since I was working with 1½″-thick (38 mm) lumber, I followed the standard rule of thumb (screw length ≈ 2× the board thickness) and went with 3″ (75 mm) screws.
Footings (post bases)
I used pre-cast concrete footings with built-in metal mounting plates (“post base anchors”) — they let you screw the support posts directly to the metal plate, which is super convenient.
At my local home improvement store these were about ¥700 each (about $5 USD).
※ Heads up: the same footings sell online for ¥2000+ each. Buying in person at a hardware store saves a lot of money on this kind of bulky item.
Building the Deck
Step 1: Assemble the joist frame and dry-fit it
Screw the joists together with stainless steel coarse-thread screws to form the frame.
Place the assembled frame in position. Leave the spots open where the support posts will go — those get added in the next step.
Step 2: Install footings and support posts
Dig down about 4″ (10 cm) at each post location, drop in an inch or two (a few centimetres) of crushed gravel, and tamp it down firmly with a piece of scrap lumber.
Step 3: Connect joists to support posts
Check for level, then screw the joists to the posts. Once that’s done, all that’s left is laying the deck boards.
A confession — I didn’t actually follow this order
OK, full disclosure: I wrote up a clean step-by-step above, but in reality I didn’t have anything to prop the joist frame up at the right height for the dry-fit, so I went ahead and screwed the front-side posts to the joists first (visible in the photo below). Do as I say, not as I did.
Step 4: Lay the deck boards (you’re done!)
Last step — screw the deck boards down across the joists.
Leave a small gap of about ⅛″–3/16″ (3–5 mm) between boards so rainwater can drain through.
I used a scrap of wood as a 3/16″ (5 mm) spacer between boards as I screwed them down.
All boards screwed down — and we’re done!
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