ud83dudcda Wood Deck Build Log u2014 13 of 45
u2190 Structural Design Pt.1: Steel Pipe Concept u00b7 Series Index u00b7 Structural Design Pt.3: Corrugated Roof u2192
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2026 Note from DIY Dad: Structural Design Overview
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Once the materials were chosen, the next step is structural design — deciding what structure to build, how the roof interfaces with the building, and what to do about railings.
Basic Structure of a Wood Deck
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- Footing (束石): placed on the ground as a foundation
- Post (束柱): stands on the footing
- Beam (大引き): laid across the posts along the long axis
- Floor joist (根太): laid across the beams, supporting the decking
- Decking board: surface material fastened to the joists
I chose a free-standing roof structure and a fence-style railing using the same decking board material.
Originally published: 2017-05-05. The decking material is SPF, which attaches to the Super Light 700 floor joists. The joint between steel pipe and SPF uses a dedicated pipe coupler — specifically the rafter clamp (垂木クランプ).
This method takes more assembly effort, but allows screws to be driven from below the deck. The top surface stays free of screw protrusions, so there is nothing to catch dust, water, or your feet.
↑ Rafter clamp (垂木クランプ)
↑ Rafter clamp assembly concept
No structural problem — but a big cost problem! Each SPF board needs 2–3 rafter clamps. With at least 50 boards needed, that means 100–150 clamps at roughly ¥200 each. Way too expensive.
I went to the home improvement store looking for an alternative. Wandering the aisles, I found it: saddle bands (サドルバンド):
↑ Saddle band (サドルバンド)
↑ Saddle band assembly concept
Hot-dip galvanized finish — suitable for outdoor use. I used the φ40 mm size and bent it slightly to grip Super Light 700 40A pipe. Price: ¥45 each — roughly one-quarter the cost of rafter clamps!
One issue: zero clearance between the Super Light 700 and the SPF boards means the pipe coupler at each joint conflicts with the SPF board. I will notch the SPF boards at each clamp location to clear the interference.
ud83dudcda Wood Deck Build Log u2014 13 of 45
u2190 Structural Design Pt.1: Steel Pipe Concept u00b7 Series Index u00b7 Structural Design Pt.3: Corrugated Roof u2192
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