ud83dudcda Wood Deck Build Log u2014 21 of 45
u2190 Detail #5: Main Beam Redesign (Updated) u00b7 Series Index u00b7 Detail #7: Floor Joist Strength u2192
2026 Update from DIY Dad: Detailed Planning and Construction Prep
ud83duded2 RECOMMENDED PRODUCTS
Pressure-Treated Deck Lumber
Pressure-treated lumber is the baseline u2014 skip it and you’ll be rebuilding in 5 years.
Once the overall structure was decided, it was time to nail down the details and prepare for construction. I carefully worked through the joinery at each connection point and finalised the materials list before placing orders. ^ ^
Key Joinery Details to Think Through
“Joinery” (u7d0du307eu308a in Japanese) means how each pair of parts meets and connects. The most critical connection points for a wood deck:
- Post-to-beam connection (screws, hardware, or mortise-and-tenon)
- Beam-to-joist connection (joist hanger hardware or screw fastening)
- Decking edge treatment (cut and exposed, or concealed with fascia board)
- Interface with the building wall (gap treatment, drip flashing)
- Roof-to-column connection (fixing method for pergola rafters)
Ground Preparation Under the Deck
The ground under the deck also needs attention u2014 without treatment, weeds will grow through. Options:
- Lay weed-control fabric (most common and affordable)
- Top with gravel (acts as ballast over the weed fabric)
- Concrete (fully eliminates weeds; watch drainage)
I went with weed-control fabric + gravel u2014 a good balance of cost, effectiveness, and ease of installation. m(_ _)m
Main Beam (u5927u5f15) Redesign: Revised Column Layout
ud83duded2 RECOMMENDED PRODUCTS
Deck Stains & Waterproof Sealers
Stain every 2u20133 years. It’s the single cheapest way to double deck lifespan.
Hi, I’m DIY Dad. ^ ^
I re-examined the beam layout with a revised approach u2014 4 posts felt like the right number for this size.
With this layout, the clear span is 1,850 mm.
u2191 Column layout u2014 6 posts (increased to 6)
Calculation
M = WL / 4 = 240 u00d7 0.5 u00d7 9.8 u00d7 1,850 / 4 = 543,900 Nu00b7mm
u03c3 = M / Z = 543,900 / 2,990 = 181.9 N/mmu00b2 > 157 N/mmu00b2 u2192 NG
u03b4 = WLu00b3 / (48EI) = 240 u00d7 0.5 u00d7 9.8 u00d7 1,850u00b3 / (48 u00d7 2.05u00d710u2075 u00d7 72,600) = 10.4 mm > 6.2 mm (L/300) u2192 NG
Both stress and deflection are still outside the allowable limits. (^^;
Maybe my load assumptions are too conservative u2014 let me rethink the approach. ^ ^
That’s all for today! (^^)/~~~
ud83dudcda Wood Deck Build Log u2014 21 of 45
u2190 Detail #5: Main Beam Redesign (Updated) u00b7 Series Index u00b7 Detail #7: Floor Joist Strength u2192
DIY Renovation Quote Review Manual
How to read, compare, and negotiate contractor quotes. This manual saved me u00a5800,000 on a single renovation project.
ud83cudfe0 More from DIY Father
15 years of landlord experience u00b7 3 apartment buildings u00b7 DIY renovations that saved millions of yen. Browse all articles at diytosan.com
