What you’ll build
Each side is a 36″ rear 4x4 post and a 24″ front post joined by a 2x4 seat rail and a 1x3 side slat. 41″ 2x4 aprons join the sides, four 1x4 supports span the seat to carry cushions, three 1x4 slats form the back, and 2x4 armrests sit on the front posts.
Shopping list
Buy these boards. The list fits every cut onto standard lengths and leaves ⅛″ for each saw cut and ¼″ for trimming board ends.
| Lumber | Length | Qty |
|---|---|---|
| 4x4 | 8 ft | 2 |
| 2x4 | 8 ft | 2 |
| 1x4 | 8 ft | 3 |
| 1x3 | 8 ft | 1 |
Cut list
All 19 parts, grouped so you can cut matching pieces together. Exact lengths and end-cut angles for every part are in the free plan in the TimberLab app.
| Part | Lumber | Qty |
|---|---|---|
| Seat Support | 1x4 | 4 |
| Backrest | 1x4 | 3 |
| Front Leg | 4x4 | 2 |
| Rear Back Leg | 4x4 | 2 |
| Rail | 2x4 | 2 |
| Rail | 2x4 | 2 |
| Side Slat | 1x3 | 2 |
| Armrest | 2x4 | 2 |
Tools
- Tape measure
- Pencil
- Speed square
- Eye & ear protection
- Drill
- Miter saw
- Clamps
- Sander
Step-by-step instructions
Assemble left side frame
Lay the 36-inch rear left post and 24-inch front left post flat on your work surface. Position the 21-inch left seat rail and side slat between the posts, keeping outer faces flush. Clamp the parts securely across the posts.
Assemble right side frame
Lay the 36-inch rear right post and 24-inch front right post flat, mirroring the first side frame. Fit the 21-inch right seat rail and side slat between the posts, aligning the faces flush. Clamp the assembly firmly in place.
Connect side frames with aprons
Install backrest slats
Fit recessed seat supports
Set the armrests
Get the full plan: all 6 steps and every cut length.
Download TimberLab and open Box-frame outdoor sofa in the catalog to get every cut length and end-cut angle, all 6 assembly steps in 3D, and Timbo, the AI build helper. Catalog plans are free to open; some features, such as AI edits, require a subscription.
For outdoor use, choose a rot-resistant or pressure-treated lumber (rated for ground contact where wood touches soil) and exterior-rated screws. Seal the end grain, build on level ground, and check the joints each season.
Change the size or design
This plan is one of the projects in the TimberLab app’s catalog. In the app you can turn the model in 3D, follow the assembly steps one part at a time, and ask for changes in plain words, such as “make it 6 inches shorter” or “add a shelf”. The cut list and shopping list update to match the new design.
Questions about this plan
How much lumber do I need to build this box-frame outdoor sofa?
The shopping list calls for 2 × 4x4 at 8 ft; 2 × 2x4 at 8 ft; 3 × 1x4 at 8 ft; 1 × 1x3 at 8 ft. It groups every cut onto standard board lengths and leaves room for saw cuts and trimming the board ends.
How big is the finished box-frame outdoor sofa?
It is 48″ wide, 36″ tall, and 28″ deep.
What tools do I need?
You need a tape measure, pencil, speed square, eye & ear protection, drill, miter saw, clamps, sander.
Can I change the size of this box-frame outdoor sofa?
Yes. Open the box-frame outdoor sofa in the TimberLab app and describe the change in plain words, such as “make it 6 inches shorter”. The 3D model, cut list, and shopping list update together.
Where can I get the full box-frame outdoor sofa plan?
The full plan, with every cut length and all 6 assembly steps in 3D, is free in the TimberLab app. Download TimberLab on the App Store and open the box-frame outdoor sofa in its catalog.
