Flat Roof vs Pitched Roof – Pros and Cons, Cost

Roofs can come in all different types - short or tall, angular or curved, asphalt, metal, or stone dressed, and in a rainbow of color choices. 

One of the biggest things that will affect how your roof looks and performs is the pitch. Your pitch is the first thing a person will notice about your home. And for most residential homes, a slanted medium slope is the way to go. In contrast, commercial properties might do best with flat and functional roof structures. 

Ooh Flat - We Like It Like That

Flat roofs are less common for residential homes, but they make a perfect choice if you want to do something functional with your roof, like make a garden, a patio, or a place to view the stars at night. In addition, this design is a frequent go-to for contemporary-style homes. 

Essentially, this roof style is seen in commercial buildings, warehouses, hotels, and apartments where there is a need for the room to store HVAC (heating, ventilation, air conditioning) units, solar panels, or other items that will need frequent access.

Flat Facts

Even if they classify as flat, all roofs will have a slight angle, which is crucial for drainage. Without a pitch, any collected water or snow would settle on the top, leading to leaks, weight strain, and potential roof collapse. Therefore, a flat roof will have a minimum of ½/12 (½:12) to 1:12 (1/12) roof pitch. 

This angle helps direct water from the center of the roof to the sides, where the water enters the gutter system to drain properly away from the roof. However, the slope might be so slight that it's undetectable. 

Flat Roof's Highs and The Lows - and How Far Your Money Goes

• Walkable (benefit)

The most significant advantage of flat roofs is that they're walkable, meaning it's easy and safe to walk on them without being dangerous to yourself or your roof. 

A walkable roof is any roof with a pitch of 7:12 or less. However, if you're interested in having additional usable space above your home, a flat roof might offer the optimal solution. 

• Costs (benefit)

Another great benefit is a lower upfront cost for installation. Flat roofs require less material, and it doesn't require as much preparation and labor, allowing for cheaper work costs and faster install. 

Installing a flat roof can cost between $4 and $13 a square foot (12" x 12") and $40 to $130 a roofing square (100 square feet). So you can spend $4,000 to $13,000 on a 1,000 square foot home, depending on materials. 

Labor costs can range from $3 to $7 a square foot, including the removal and disposal of old roofs. If you want a multi-layered roof, expect an additional $1 to $2 for each extra layer.

• Lifespan (downside)

There are also a few downsides to flat roofs. In terms of longevity, a flat roof has a shorter life expectancy of 10 years, meaning you'll have to do multiple roof replacements during your years of ownership. 

• High Maintenance (downside)

A flat roof also requires more frequent maintenance than a roof with a slope. You should plan to do yearly inspections to check for signs of damage. Although it might also be necessary to do checks after periods of intense snow or rain. 

You have to check the gutters and the flashing every six months and sweep the roof every few months, as flat roofs have a higher propensity to trap leaves and other debris. 

You also have to do reseals of the roof surface, which can cost $400 to $1,800, and re-caulk flashings and roof joints that show signs of cracks.  

• Easy Inspections and Repairs (benefit)

On the plus side, flat roofs are easier to inspect and will cost less to hire a professional due to the ease of walking on them. And repairs are also more affordable, ranging from $300 to $600 for minor repairs to over $1,000 for storm damage or major repairs.

• Leak-Prone

Flat roofs are also at increased risk of developing leaks. Roofs with little to no slope have a harder time shedding moisture. Having puddles of water or snow that sit in puddles on the roof without draining can cause leaks, cracks, and damage to your roof.

Yo Pitch - Why You Slanting?

Pitched roofs are more common in residential homes than flat roofs, although plenty of commercial buildings incorporate the design into their rooflines instead of a flat roof. 

The biggest reason people prefer pitched over flattened is the variety of styles you can get with a roof with slants and angles (more than 20-degrees to classify as a pitch). But a roof's slope can also affect how the top handles drainage from rain and heavy snow. 

How's It Pitching?

A roof's pitch is the dividend of the roof's vertical rise divided by the horizontal span and defines the roofline's steepness. This pitch is written as a ratio where the first number is the inches that the roof rises while the second number classifies the horizontal area (usually 12"). 

Roofs can fall into one of three categories to define their roof pitch (four if you include a flat slope of ½ to 1/12. 

• Low slope: These roofs will have a pitch of 1:12 to 4:12 and require particular installation to block leaks while protecting against foot traffic. 
• Medium slope: Roofs with a pitch of 4:12 to 9:12 (1:3 or 3:4) have a medium slope and are the most traditional style, with most homes having a 6:12 pitch. 
• Steep slope: Roofs with a 10:12 pitch or higher are steep-sloped, making them challenging to walk on (therefore challenging to do inspections and repairs) and require particular installation and limitations on material types you can use.

Hold up! Get a tape. Here's how you can estimate:

Want to know how to calculate your roof's pitch? Check out these three easy methods to DIY the measurements. 

Pitch Roofs Highs and The Lows - and How Far Your Money Goes

• Better For Weather Protection (benefit)

Roofs with a pitch provide better elimination of precipitation. A pitched roof might perform better than a flat roof if you live in a climate with many heavy rainstorms or snowfall. This is because the slope of the roof helps the precipitation slide off rather than pooling up. 

• More Choices (benefit)

You also have a wider choice of materials, colors, and designs available. For example, sloped roofs can hold asphalt shingles, metal roofing, clay, composite shingles, wood shakes, or slate.   

• Specialized Performance (benefit)

Many of these materials can have additional benefits like Class 4 impact resistance to protect against hail damage and high wind ratings suitable for hurricane-prone locations.

• More Architectural Style Options (benefit)

Pitched roofs also give you more options on architectural style. Pitched roof styles include hip, dome, gambrel, mansard, and gables, among others. 

The various materials and slope ratios also allow pitched roofs to have longer lifespans than flat roofs. Plus, you'll save money by not having to replace your roof as often.

• More Expensive (downside)

A downside of pitched roofs is you might spend the same amount or slightly more money for installation, depending on materials. 

And the steeper your pitch, the higher the price will be for labor costs and materials. If you want to DIY a roof replacement, you'll have an easier time with a medium slope roof versus a steep pitch. The graph demonstrates material costs by square foot, not including accessories. 

Forget the Flat and Switch to Pitch

It's possible to convert a flat roof to one with a pitch. But this is not a DIY undertaking, so you will have to pay for labor costs plus additional materials. 

To start the raised structure that will support the roof (and create the attic space), you'll have to buy tresses, which you can get for as low as $1 a square foot. 

You may also spend between $1,700 and $8,000 for new roofing supports and $1,000 to $10,000 for new roof framing. Then, finally, you'll have to pay for the materials.