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Contractor glossary

Roof pitch

Updated

Definition

Roof pitch is how steep a roof is, written as the inches it rises for every 12 inches of horizontal run, such as 6/12. Pitch decides how much real surface sits over a footprint, how fast crews can work and what safety setup and materials the roof needs.

Also called: Roof slope

How pitch is written

A 6/12 roof (said "6 in 12") climbs 6 inches for every 12 inches it runs horizontally. The bigger the first number, the steeper the roof, and 12/12 is a 45-degree slope. Apps and angle finders often read in degrees, so it helps to know both. The pitch factor is how much real roof surface sits over each square foot of flat footprint.

Pitch Angle Pitch factor
3/12 14.0° 1.031
4/12 18.4° 1.054
6/12 26.6° 1.118
8/12 33.7° 1.202
10/12 39.8° 1.302
12/12 45.0° 1.414

The factor is the square root of (rise squared plus 144), divided by 12.

How to measure it

  • On a walkable roof: rest one end of a level on the roof surface, hold it level pointing downslope and measure straight down from the 12-inch mark to the roof. That measurement in inches is the rise: 7 inches means 7/12.
  • From the attic: hold one end of the level against the bottom edge of a rafter, level it toward the ridge and measure straight up from the 12-inch mark to the rafter. It keeps you off a steep or wet roof.
  • From a report or an app: aerial measurement reports list a pitch for each plane, and phone apps read degrees. Check at least one plane by hand before you price from either.

Why pitch changes the price

  • Material quantity. A footprint measured from the ground or a plan is flat, and the roof isn't. Multiply the flat area by the pitch factor to get the real surface, then add waste.
  • Labor and safety. Steeper roofs slow every task, from carrying bundles to setting fall protection anchors. Price steep or high sections as their own labor line, set from your crews' real production on similar roofs.
  • Material choices. At the low end, check the shingle manufacturer's minimum slope and your local code before you price a porch roof or addition. A section below the minimum needs a different roofing system.

Example: A house has a 2,000 square foot footprint, overhangs included, and every plane is 8/12. The pitch factor is about 1.202, so the roof has 2,000 × 1.202 = 2,404 square feet of surface, about 24 roofing squares before waste. Price it off the footprint and you'd order 20 squares and come up about 4 squares short.

Common mistakes

  • Pricing from the footprint without the factor. On an 8/12 roof, the real surface is about a fifth bigger than the footprint.
  • One pitch for the whole roof. Porches, dormers and additions often differ from the main roof. Measure and price each section at its own pitch.
  • Mixing up degrees and pitch. A roof an app reads as 30 degrees is about 7/12.
  • Scaling hips and valleys off a plan. They run on a diagonal, so neither the plan view nor the common pitch factor gives their true length. Measure them or take them from a report.

How it connects

Pitch is what turns a measured footprint into squares, and it drives the steep-roof labor and safety lines in an estimate. On insurance work, a scope written with a lower pitch than the roof really has can undercount both the squares and the steep-roof labor, so document the measured pitch with photos when you request an insurance supplement. For the full method, see how to price roofing jobs and how to write a roofing estimate.

Go deeper

Roofing guideHow to Price Roofing JobsPrice roofing jobs from real measurements: squares, pitch factors, waste, tear-off layers, decking allowances, code line items and insurance work.Roofing guideHow to Write a Roofing EstimateWhat goes in a roofing estimate: squares with pitch and waste, line items adjusters expect, code items, decking allowances, photos, warranties and payment terms.Roofing guideHow to Start a Roofing BusinessWhat a new roofing company needs first: the right state license or registration, insurance, OSHA fall protection and training, a supplier account and a debris plan.Roofing guideHiring Your First Roofing EmployeeWhat changes when a roofing company hires its first employee: OSHA fall protection training, gear you must pay for, heat safety, comp and real labor cost.
Roofing squareA roofing square is 100 square feet of roof surface. Roofers measure roofs, order materials, price labor and compare jobs in squares, so a roof with 2,400 square feet of surface is a 24-square roof.Fall protectionFall protection is the equipment, setup and training that keep workers from falling, or stop a fall safely, when they work at height. In residential construction, OSHA requires employers to protect each employee working 6 feet or more above a lower level, usually with a guardrail, safety net or personal fall arrest system.EstimateAn estimate is a contractor's expected price for a job, based on the scope as it's understood before work starts. It tells the customer the price could change if the work turns out different, but whether it binds you depends on its wording, the customer's acceptance and your state's law.Insurance supplementAn insurance supplement is a request, made on the homeowner's claim, asking the insurer to add work or quantities its original estimate missed. On a roof, it usually covers items found at tear-off or measured short, backed by photos, measurements and line-item prices.

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