Single Slope Carport: Heights, Implied Pitch and Price

What does single slope mean on a carport?

A single-slope carport has one roof plane that falls from a high side to a low side, so all roof water and snow leave at one edge. A gable roof has a center ridge and two low sides, and a single-slope roof has neither. Sellers offer the shape two ways: with the high side on a wall, or as a roof on its own posts. A shed roof can also cover a carport with a shed attached, which has a guide of its own.

What else is a single-slope roof called?

A single-slope roof has several names, and each describes the same shape: one plane, one high side, one low side. Lean-to usually names a roof that leans on one wall, and sellers also use the word for builds on their own posts. Skillion is the Australian and New Zealand word, and monoslope is the wording ASCE 7 uses, which matters only in the wind section below. Listings titled lean-to, shed roof or single pitch can all describe the same roof.

How do single-slope listings print leg heights and price?

The single-slope listings read for this guide print a width, a length and two leg heights, and none prints the roof pitch. Table 2 lists eight listings read on October 5, 2026, with the pitch each pair of heights implies. The Pro Metal Buildings row is a 12x20 carport with a 9 ft and a 7 ft side.

Legacy Carports prints the size code 18x25x12x9 and a 9 ft eave leg height. It does not define the 12 or say which side is the span. If the 12 is a high-side height, 3 ft of drop is 2:12 across 18 ft and 1.4:12 across 25 ft, so the table shows no pitch for that row. For the other rows, the first printed width is taken as the span, the first printed height as the high side, and the slope as running across the span. A seller's own pitch could differ if the heights are measured another way.

Every price in Table 2 is the seller's own, published on the date read. CarportBay's manufacturer and dealer guide explains how builders, dealers and installers differ, so a reader can tell who stands behind a price. The eight listings are metal builds, and the guide to metal carport gauge and coating explains the gauge numbers.

What pitch do those heights work out to?

Pitch is the rise in inches for every 12 inches of run, and it can be worked out from the two leg heights and the width. Subtract the low side from the high side, divide by the width in feet, and multiply by 12. The Pro Metal Buildings listing has a 9 ft and a 7 ft side across 12 ft. That is 24 in of rise over 144 in of run, which is a 2:12 pitch and an angle of 9.5 degrees.

Pitch (in per 12 in) = (high side ft - low side ft) / width ft x 12. For 9 ft, 7 ft and 12 ft: (9 - 7) / 12 x 12 = 2, so 2:12.

The guide figures sit beside that range. Plus Fabrication names 1:12 to 5:12 for a single slope (June 4, 2026). Hansen Pole Buildings says most steel roofing manufacturer warranties are void on slopes under 3/12 (updated March 26, 2025). The Carport Co recommends 4/12 where the budget allows (modified October 4, 2026). All seven implied pitches are below 3:12, so the minimum slope for the panel on a given listing is a question for the seller. The guide to metal lean-to carports covers panel minimums. The seller sets the pitch, so ask for it in writing.

What do sources say about snow and wind on a single-slope roof?

Sources split on how a single-slope roof handles snow, and ASCE 7 treats a freestanding monoslope roof and a canopy attached to a building as different wind cases.

ASCE 7 is the loading standard that building codes such as the International Building Code use for design wind and snow loads. An ASCE committee exchange of March 2023 says section 30.5 covers free-standing monoslope roofs and section 30.9 covers canopies attached to a building. An International Code Council slide lists section 27.3.2 of ASCE 7-22 as Open Buildings with Monoslope, Pitched, or Troughed Roofs. Which section applies to a given carport is a question for the stamped plan, as it is for attached carports.

On snow, Hansen Pole Buildings (2014) says a single slope sends snow to one eave and warns of weight piling against the low wall. Plus Fabrication (June 4, 2026) says snow piles on the low side and can stress the roof unevenly, while a double slope shares the load. The Carport Co (modified October 4, 2026) recommends a 4/12 pitch because a shallower roof sheds snow more slowly. Interlock Roofing (updated September 4, 2026) says a continuous slope promotes rapid snow shedding and that a low slope is prone to snow buildup in cold climates.

Seller labels differ. Legacy Carports prints Engineer Certified for 140MPH / 35PSF, and Absolute Steel prints 90 mph and 30 psf. Plus Fabrication names 90 mph and 30 psf as its standard. Pro Metal Buildings, United Carports and C&H Carports print no rating on the pages read. None prints a code edition, so ask for the edition, for example ASCE 7-16 or ASCE 7-22, and for the stamped plan.

Stamped plans and the local building department set the load figures for a site.

Which questions settle a single-slope order?

Six questions put to a seller settle most single-slope carport orders.

1. What is the roof pitch, in inches of rise per 12 inches of run?
2. What are the high-side and low-side leg heights, and which side is the span?
3. What minimum slope does the panel maker allow for this panel?
4. Which wind and snow rating applies, under which ASCE 7 edition, and is a stamped plan included?
5. Which way does the low side face, and where does a gutter go?
6. What does the local building department require?

If side walls are planned, ask how adding side walls changes the rating.

The 2021 International Residential Code, section R105.2, exempts one-story detached accessory structures up to 200 sq ft of floor area from a permit, as reproduced by Grant County, Washington. Local rules can be stricter, and the guide to permit rules for carports lists more.

This page provides general information about permit and code requirements based on publicly available sources cited above. Building codes and permit requirements vary by jurisdiction and change over time. This is not a substitute for confirming current requirements with your local building department or consulting a licensed contractor or engineer for your specific project.