I built this deck for my mother as a 70th birthday gift.
The brief from her was simple: “I want somewhere I can air out futons.”
For my own backyard’s deck I’d used SPF lumber, but for this one I wanted a bit more long-term durability — so I went with Western Red Cedar.
WRC is a popular choice for outdoor decking: it’s a softwood and easy to work with, but holds up to weather a lot better than typical SPF.
(For reference, my own DIY deck at home is SPF — write-up → here. It also covers the basic deck-construction terminology in case any of the words below are new.)
For readers outside Japan: many Japanese homes use futon — a thick padded mattress laid directly on the floor at night and stored away during the day. Routinely hanging futons over a railing or sturdy fence in the sun is a normal part of household care: the airing dries out moisture and helps keep the bedding fresh. The fence on this deck is sized specifically for that — 1.2 m above the deck, with a sturdy top rail to drape futons over.
This write-up walks through the structural design, the lumber and tools used, the actual build steps, and the costs as I went. (And honestly, building a deck is incredibly satisfying!)
Planning
This is the spot where the deck is going.
There’s already a concrete pad here, so the deck will sit on top of that.
Deck size
Decking footprint: 2.7 m wide × 1.4 m deep.
Futon-airing fence: 1.8 m wide × 1.2 m tall (above the deck surface).
Basic structure
Concrete underneath, but I still set deck blocks under the posts as shown in the diagram.
The blocks have integrated metal post-bases (a “haneita” plate) so the post can be lag-screwed to the block. The three posts that double as fence posts are taller than the rest.
Posts: 90 × 90 mm (4×4) Western Red Cedar
Deck blocks: with built-in post-base bracket, 15 cm tall
The deck-board support structure (joists) is laid out as in the diagram below.
Joists: 39 × 140 mm (2×6) Western Red Cedar
For decking, I used “1.25×6” — a thicker decking-specific board, 25 mm thick.
Decking: 25 × 140 mm (1.25×6) Western Red Cedar
The horizontal top rail of the fence (the bit that the futon actually drapes over) is a 2×4.
Fence top rail: 39 × 89 mm (2×4) Western Red Cedar
Sourcing the lumber
I ordered the lumber from “Mokko Land” online.
Everything is Western Red Cedar. Here’s the order:
Decking
1.25×6 25 × 140 × 1800 mm × 20
Posts
4×4 (3 ft) — 90 × 90 × 900 mm × 2
4×4 (5 ft) — 90 × 90 × 1500 mm × 3
Joists
2×6 — 39 × 140 × 3000 mm × 6
2×6 — 39 × 140 × 1500 mm × 2
Fence top rail
2×4 (7 ft) — 39 × 89 × 2100 mm × 1
Lumber subtotal: 81,170 yen
Shipping: 8,000 yen
(As of 2022, Japan was deep in the post-pandemic “wood shock” — lumber prices were notably elevated, so this would have been cheaper a few years earlier or a few years later.)
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