Need Help Deciding Between a Flat Roof and a Sloped Roof? Here’s What to Know

Whether you’re building a new home or doing a major overhaul of your current home’s roof, both flat and sloped roofs have their advantages and drawbacks. We break down the key factors to consider when choosing between a flat roof and a sloped roof.

What’s the Difference Between a Flat and a Sloped Roof?

As their names indicate, a flat roof is a flat surface, whereas a sloped roof is pitched or angled. Flat roofs are usually seen in metropolitan areas and contemporary design concepts, whereas sloped roofs tend to be atop traditional single-family homes. They both have pros and cons that you should consider before making your decision.

Why Pick a Flat Roof?

From energy savings to sky-high gardens—there are plenty of reasons to fawn over flat roofs.

Flat Roofs Are More Energy Efficient

Some homeowners are opting for flat roofs because Energy Star considers them more energy efficient. The Department of Energy classifies flat roofs as cool roofs, which are roofs with the greatest potential reflective surface area. Flat roofs are also more solar-panel friendly because the panels can be positioned in a way that provides more direct sunlight than sloped roofs.

Flat Roofs Allow for Rooftop Planting

Flat roofs also allow for the planting of a “green roof,” or rooftop garden. Green roofs are particularly energy efficient because they provide shade and remove heat from the roof’s surface and surrounding air. The U.S. Environmental Protection Agency and Energy Star champion green roofs for reducing heat islands, which are concentrations of heat that happen in metropolitan areas. One drawback to planting vegetation on your roof is that the living roots of plants can burrow into your roof, causing structural damage.

Flat Roofs Are Less Expensive

If cost is playing a large role in your roof design choice, flat roofs clock in at significantly less to install than sloped roofs. This is simply because there’s less surface area on a flat roof than a sloped roof. 

On average, flat roofs cost between $3,200 and $10,700 to install, or $4 to $13 per square foot. Sloped roof installation runs between $5,800 and $12,500. Costs will vary depending on the square footage of the roof and the materials you choose. 

However, the maintenance of a flat roof will add up to more over the life of the home, which you should factor in when calculating your expenses. Any standing water that accumulates when it’s raining or snowing needs to be addressed immediately so it doesn’t leak into your home. Heavy snow can also accumulate and cause leaks, so monitoring during the winter is very important.

Splitting is also a common problem for flat roofs, which use asphalt or felt coverings, as opposed to sloped roofs, which use slate or shingles. This happens when the material pulls apart and can also be a source of leaks into your home.

Flat Roofs Offer More Outdoor Living Space

Even if you don’t choose to make your flat roof “green,” you can use the space as a patio area, depending on the materials it’s built from. Rubber, plastic, and rubber foam are all good options for laying the foundation to create an outdoor patio space. Thermoplastic polyolefin (TPO) is a newer rubber roofing material that does an excellent job reflecting heat off of flat roofs. TPO roofing costs between $5,200 and $21,000 to install.

On the flip side, flat roofs are more sensitive to the movement of people on them, so if you’re planning to hang out on the roof, you may create a lot of noise for anyone inside your home. A good way to combat the noise problem is to have your contractor put a deck on the roof to create some separation. It’s also important to be mindful of patio furniture, which can easily puncture the roof and lead to leaks. Increased foot traffic can also cause the roofing material to age more quickly. One workaround is to install a “floating deck” on top of a roof, being careful not to put any fasteners through the roofing materials.

Flat Roofs Are Easier to Clean and Inspect

Even though flat roofs generally require more maintenance and upkeep, that maintenance is more easily performed than sloped roof maintenance. They are also easier to inspect.

Flat Roofs Look More Modern

With their clean lines and minimalist appearance, flat roofs are often used in more contemporary-looking homes. If you’re looking for a modern look, a flat roof is your best choice.

Signs a Sloped Roof Might Be for You

Choosing between a sloped roof and flat roof depends on what details are most important to you.

Sloped Roofs Have a Longer Life Span

A sloped roof can last you upwards of 30 to 50 years, depending on the material and the climate you live in. That’s compared to the life of 12 years to 15 years maximum that a flat roof offers.

Sloped Roofs Are Good for Snowy Climates

Flat roofs, by design, allow rain and snow to pool on their surfaces. They can also form ice dams, which is a ridge of ice that forms at the edge and prevents water from draining off the roof. If water is not removed within 48 hours, the roof can spring leaks and cause structural damage to your home by causing wood rot, attic leaks, and other problems. Sloped roofs allow for the natural runoff of water and are less likely to form ice dams at the edges.

Sloped Roofs Require Less Maintenance

Since sloped roofs don’t collect water as easily as flat roofs, they usually require less maintenance over their lifetime. Shingles are also more easily replaced on a sloped roof as opposed to resealing a flat roof or repairing a damaged membrane. Flat roofs need a waterproof seal to keep out moisture, and that requires maintenance to ensure that it’s functioning properly.

Sloped Roofs Need Fewer Inspections

Both flat roofs and sloped roofs should be inspected at least once per year. However, the life span issues associated with flat roofs may necessitate more frequent inspections. If you see standing water, for example, an inspection is necessary to address the issue quickly so it doesn’t become a problem. While sloped still need to be inspected regularly, they tend to have less structural problems than flat roofs.

How Much Does Roofing Installation Cost?

You should hire a local roofer to install your roof as there are several risks involved with a DIY roofing installation, from damaging your framing to hurting yourself. On average, hiring a pro to install a roof costs between $6,000 and $13,000. The price of roof installation largely depends on the square footage of the roof, and removing an existing roof may cost more.