If you have narrowed your shortlist to two specific designs, this is exactly the kind of decision where a side-by-side spec view saves a weekend of second-guessing. Both plans below are complete, code-aware DIY builds, but they differ on the things that matter for a backyard project — total cost, raw labor hours, footprint, and the wood species on the cut list.
Side-by-side specs
| 12x20 ft Arched-Top Pergola Plan | 12x20 ft Farmhouse Pergola Plan | |
|---|---|---|
| Category | Pergolas | Pergolas |
| Style | Arched-Top | Farmhouse |
| Footprint | 12x20 ft (240 sq ft) | 12x20 ft (240 sq ft) |
| Wood species | Douglas Fir | Composite (Trex / Azek) |
| Roof finish | corrugated polycarbonate panels | open lattice rafters |
| Difficulty | Intermediate | Advanced |
| Build time | ~24 hrs | ~108 hrs |
| Materials cost | $5,100–$7,975 | $12,900–$20,150 |
| Footing depth | 36″ × 4 posts | 36″ × 4 posts |
| Concrete | 8 × 60-lb bags | 8 × 60-lb bags |
| Cut-list items | 5 | 5 |
| Build steps | 11 | 11 |
Cost & budget
The 12x20 ft Arched-Top Pergola Plan lands in the $5,100–$7,975 range for materials in Douglas Fir, while the 12x20 ft Farmhouse Pergola Plan runs $12,900–$20,150 in Composite (Trex / Azek). The first plan is approximately 153% more expensive at typical 2026 lumber-yard pricing — driven mostly by the choice of Composite (Trex / Azek) over Douglas Fir and the difference in cubic concrete volume between 4 and 4 footings.
Labor & difficulty
At ~24 hours, the 12x20 ft Arched-Top Pergola Plan is rated Intermediate. The 12x20 ft Farmhouse Pergola Plan takes ~108 hours and is rated Advanced. The labor delta is roughly 84 hours, or one extra working day on the 12x20 ft Farmhouse Pergola Plan. If you are newer to outdoor woodworking, the 12x20 ft Farmhouse Pergola Plan is the safer pick — it uses simpler joinery and fewer compound cuts.
Footprint & site fit
At 240 sq ft vs 240 sq ft, you are choosing between a full outdoor room and a full outdoor room. Allow at least 24 inches of clearance on every side for furniture and walking paths — that means the 12x20 ft Arched-Top Pergola Plan needs a clear area of approximately 16×24 ft and the 12x20 ft Farmhouse Pergola Plan needs 16×24 ft.
Material & durability
The 12x20 ft Arched-Top Pergola Plan is built from Douglas Fir, while the 12x20 ft Farmhouse Pergola Plan calls for Composite (Trex / Azek). The species choice drives the cost delta and the maintenance schedule. Pressure-treated southern yellow pine is the cheapest and most rot-tolerant for in-ground posts; western red cedar is the DIY favorite for visible parts; redwood and white oak are heritage choices that command a premium.
Verdict
For a builder weighing these two specifically, 12x20 ft Arched-Top Pergola Plan is the clear budget pick. If both fit your budget and yard, default to the design whose style language matches the rest of your house — a Craftsman bungalow looks awkward beside a modern slatted pergola, and vice versa.
Read each plan in full before committing: the complete 12x20 ft Arched-Top Pergola Plan page and the complete 12x20 ft Farmhouse Pergola Plan page. Both ship with full cut lists, hardware schedules, footing specs, and step-by-step build instructions.