Reviewed 3 min read3 primary sourcesVersion 1.3
Written and reviewed by Pergola Wiki Editorial TeamSee editorial method and revision history
Pergola rainwater path from roof surface through gutter, downpipe and safe discharge
Water performance depends on every link from collection to safe discharge and overflow. Original diagram by Pergola Wiki.
Read a detailed text description

Arrows follow rainfall from the roof or closed louvers to falls and joints, then into gutters, outlets and downpipes before reaching a safe discharge point. A separate overflow path represents the backup route needed when the primary outlet is blocked or rainfall exceeds the assumed capacity.

Key takeaways

  • Every load needs a complete path.
  • Notches and holes can reduce capacity.
  • Frame geometry controls stability as well as appearance.

On this page

  1. Roles
  2. Coordination
  3. Read the frame as a hierarchy
  4. Alignment is performance evidence

Roles

Rafters or louvers collect local actions, beams gather them, posts carry combined vertical and lateral effects, and bases deliver reactions to foundations. Connections must transfer the forces assumed in the design model.

Coordination

Lighting channels, gutters, concealed wiring and decorative cuts should be coordinated before fabrication. Field drilling at a highly stressed zone can invalidate the intended section behavior.

Source tier 2Source-register entry
The Aluminum Association — Aluminum Design Manual 2020
Structural aluminum design reference cited by the International Building Code.

Read the frame as a hierarchy

Roof elements deliver reactions to rafters or louvers, then to beams, posts, bases and soil—or into an attached building. A discontinuity anywhere can govern the system. Decorative sleeves and internal gutters often conceal the actual joint, so inspection and documentation should identify the load-bearing component rather than the visible cover.

Alignment is performance evidence

Out-of-plumb posts, beam twist, unequal diagonals and inconsistent roof falls can indicate erection error, foundation movement or connection slip. Establish tolerances before installation and record a baseline at handover. Later comparison is more reliable than judging movement from memory or a single photograph.

Source tier 2Source-register entry
American Wood Council — 2024 National Design Specification for Wood Construction
ANSI-approved wood design standard referenced by 2024 US model codes.

Primary sources and scope

Source tier 2Source-register entry
The Aluminum Association — Aluminum Design Manual 2020
Structural aluminum design reference cited by the International Building Code.
Source tier 2Source-register entry
American Wood Council — 2024 National Design Specification for Wood Construction
ANSI-approved wood design standard referenced by 2024 US model codes.
Source tier 2Source-register entry
American Society of Civil Engineers — ASCE/SEI 7-22 — Minimum Design Loads and Associated Criteria
Official standard hub for US structural actions including wind, snow, rain, seismic and load combinations.

Cite this page

Pergola Wiki Editorial Team. “Posts, beams and rafters.” Pergola Wiki. Reviewed 24 July 2026. https://pergola.wiki/articles/posts-beams-rafters/

Professional boundary: This article cannot replace a site investigation, project-specific manufacturer documentation, structural calculations or the authority having jurisdiction.
Disclosure: the site footer contains one labelled industry link to Oscar Pergola. It does not determine article conclusions, source tiers or product rankings. Read the full disclosure。