Read a detailed text description
The diagram branches from the shared name “pergola” into three overhead conditions: an open frame that lets rain pass, an operable cover whose state changes, and a continuous roof that collects water. Each branch then points readers to verify attachment, enclosure, services, structural actions, drainage and the local approval pathway.
Key takeaways
- Open overhead framing defines the classic form.
- Shade changes with spacing, depth, orientation and season.
- Adding a solid roof may change the legal classification.
On this page
Form and performance
Posts and beams support rafters or slats with open sky between them. The structure frames outdoor space and can support planting, lighting or removable fabric, but rainfall normally passes through. Shade should be described as variable rather than complete.
Design boundary
The same word can describe different structures in different markets. A local authority may distinguish an unroofed pergola from a patio cover or roofed outbuilding, so terminology alone does not determine permit status.
A jurisdiction-specific example showing that “pergola” may mean an unroofed structure.
Geometry is the shade control
For an open frame, the most useful specification is geometric: rafter direction, member depth, clear spacing, overall height and the hours or seasons when shade matters. A shallow, widely spaced frame may look substantial in elevation while casting little midday shade. A deeper member can cast a longer shadow without closing the sky, but wind area and connection forces also change.
Inspection and change control
Check for rafter rotation, loose plant supports, trapped debris and later additions such as polycarbonate sheets or fabric. Retrofitting a cover changes rain collection, uplift, connection forces and sometimes the legal classification. Treat that change as a new design decision rather than a cosmetic accessory.
Government guidance on orientation, daylighting and shading.
Primary sources and scope
A jurisdiction-specific example showing that “pergola” may mean an unroofed structure.
Government guidance on orientation, daylighting and shading.
US model-code provisions for residential patio covers; only applicable where adopted.
Cite this page
Pergola Wiki Editorial Team. “Traditional open-rafter pergolas.” Pergola Wiki. Reviewed 24 July 2026. https://pergola.wiki/articles/traditional-open-rafter/