Roof pitch or slope describes steepness, shown on US drawings as inches of rise per 12 inches of run, and sometimes as an angle or a percentage. Because a roof framing plan is a top-down view, it uses slope notes and direction arrows rather than showing the full vertical geometry. Notation varies, so the drawing legend and project specifications control.

Pitch vs. slope

The two terms are often used interchangeably in the field, although some standards define them more narrowly: slope is stated as rise per 12 units of run, while pitch has historically meant rise over the full span. On a drawing, avoid ambiguity by stating the actual ratio, angle, or percentage and its direction.

  • Rise-over-run notation, such as 6:12, states inches of vertical rise per 12 inches of horizontal run.
  • Angle notation states degrees from horizontal.
  • Percentage slope states rise divided by run, multiplied by 100.

These formats describe geometry. They do not by themselves establish drainage performance, roof-covering suitability, snow behavior, or structural adequacy.

How pitch appears on a plan

Because a framing plan is drawn looking straight down, you don't see the slope directly, so it is annotated:

  • A small slope triangle giving the rise over a 12 inch run, such as 6:12, or the angle.
  • A slope arrow showing which way water drains.
  • Spot elevations or notes at ridges, hips, valleys, high points, low points, and roof drains where needed.

This is the same annotate-what-you-can't-draw principle used for other out-of-plane information.

Why pitch changes the framing

Slope affects roof geometry, drainage, covering selection, member lengths, and load effects, but it does not dictate one structural system:

  • A pitched roof may use rafters, trusses, frames, or other systems. See rafters vs. trusses.
  • A low-slope roof may use joists and a deck, sloped rafters or trusses, steel framing, concrete, or another system. The drainage slope may be built into the structure or formed above it.
  • Roof-covering products have their own minimum and maximum slope conditions, which must be coordinated with the design and local requirements.

As a model-code example, not a universal rule, the 2024 International Building Code lists roof-covering-specific slope and drainage requirements. For one- and two-family homes, roof and ceiling framing sits in IRC Chapter 8. Use the edition and amendments adopted for the actual project, plus the selected roof-covering manufacturer's requirements.

A note on the tool

Framing Plan can record a plan-view footprint, member field, support assumptions, openings, and slope notes. It is most directly reusable when a preliminary roof concept uses joist-like repeated members. It does not select a roof covering, calculate drainage, or design rafters, trusses, wind restraint, connections, or ponding resistance.

Keep it preliminary

Use a preliminary plan to record the intended pitch, slope, and layout. The structural design, meaning member sizes, drainage, and connections, must be confirmed by a qualified engineer for your project and for the code adopted in your jurisdiction.

Try it

Lay out a low-slope roof or annotate a roof's slope in the browser. Open the framing studio, or read the flat roof framing plan guide.