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Providence: What Do You Need to Know About Roof Geometry?

Mar 03, 2019

Mansard, gambrel, skillion – chances are, these terms were unfamiliar to you, even when you began your journey in search of a new roof. In fact, most people don’t think much about their roofs beyond the necessary maintenance and eventual replacement costs. However, whether you’re building a new home in Providence, completely replacing an existing roof, or simply looking to exchange your roofing materials for something more durable, roof geometry is important to understand.

This guide to roof geometry will describe the most common roof shapes, along with their pros and cons – what we like to call the good, the bad and the ugly. In addition, we will list ideal roofing materials for each type. Finally, we’ll provide a brief primer on roof pitch and what you need to know when deciding on a roof for your home.

Gable Roof

If you’ve ever seen a child’s drawing of a home, think back to the roof – likely triangular in shape from the front with a symmetrical slope down each side, children often draw what we know as gable roofs. Gable roofs are the most commonly-used roof design in the U.S., and for good reason – they’re attractive, fairly worry-free in most areas and, if kept simple, are among the least costly.


• Side gable roofs are fairly identical to classic gable roofs, though the gable triangles are at the sides of the home instead of the front and back.
• Crossed gable roofs have gables at right angles to each other, in a variety of different styles. Gables are usually used to accent additional areas of the home.
• Front gable roofs have an additional gable above the main entrance of the home.
• Gables can also be added to dormer windows at the builder’s discretion.

The good: Gable roofs are comparatively inexpensive, owing to their simple design and relative lack of extra materials. Their fairly high pitch allows a decent amount of space on the upper floor and allows easy shedding of snow and water.

The bad: Gable roofs, especially simple gable roofs, are fairly commonplace and may lack the aesthetic features you’re looking for. However, consider one of the subtypes of gable roofs for a little more interest.

The ugly: If you live in a high wind or hurricane-prone area, a gable roof may not be your best choice. The classic overhang on the front face of a gable roof is susceptible to trapping wind underneath, creating lift. In a high wind situation, lift can tear a roof away.

Hip Roof

Hip roofs are the second most common type of roof in the United States, also due to their simple nature. Sloping equally on all four sides, hip roofs simply form a rectangle on two sides, triangles on the others, and come together at the top. When adding an additional wing onto your Providence home with a hip roof, the builder must simply add another hip roof, and a valley to join the two together.

The good: Hip roofs are not as wind-prone as gable roofs and are sturdier overall. Their relatively steep pitch allows snow and rain to slide off easily.

The bad: Hip roofs are more expensive than some other roof types, since they require more building materials. They’re also not as aesthetically unique as some other roofs, though some choose to add dormers to promote visual interest.

The ugly: When adding another wing, dormers, or other visual intrigue to a hip roof, you create additional valleys where the sections meet. Rain and snow can pool in valleys and cause issues.

Jerkinhead Roof

A jerkinhead roof is actually a bit of a combination between a gable roof and a hip roof and can appear as a gable roof with turned down gables in a hip style. Known also as a clipped gable roof, a jerkinhead roof’s extra features as compared to gable and hip roofs result in increased aesthetic appeal for many people.

The good: Jerkinhead roofs have the features of a gable roof without the increased risk of wind damage. Since the gables are clipped, wind cannot lift the roof at the gables.

The bad: Complex jerkinhead roofs with varied slopes and valleys increase both design and building costs.

The ugly: Multiple valleys in more complex jerkinhead roofs provide more areas susceptible to rain pooling and leakage.

Saltbox Roof

Technically a variation of a gable roof, saltbox roofs have one standard side ending above the second floor and one long side extending down to the first floor. A saltbox can be described as a gable roof home with a lean-to on the back side, where the roof flows seamlessly down to cover the lean-to. Saltbox homes are common in New England but continue to pop up throughout the rest of the country, even in the Providence area.

The good: Similar to gable roofs, saltbox roofs are durable against rain and snow, since both can easily slide off the steeper-pitched roofs. They are also more stable than traditional gable roofs, owing to the longer side of the roof’s providing additional support.

The bad: Any extra living space added by a saltbox roof is minimal, since the space in the lean-to is often one-story with a slanted ceiling.

The ugly: Saltbox roofs are typically more expensive to build and maintain, due to extra materials and additional design work.

Gambrel Roof

Gambrel roofs are often referred to as barn roofs, and it’s easy to see why – most barns and farmhouses are also roofed in a gambrel style. A gambrel roof has two different slopes on two sides of the home – a shorter, shallower slope at the top, and a longer, steeper slope down the side. Some homeowners choose to use roofing materials on the steep slope, while others, depending on the way the steep sides blend into the actual sides of the home, cover the area with traditional siding.

The good: Gambrel roofs are relatively simple to build, so they are among the less expensive roof types, and allow more space on the top floors than other types.

The bad: Obviously, barn-style roofs are not for everyone. In addition, the extra space in the top floor comes at the cost of windows, since two entire sides of the home are covered in roof. Dormers are often added, but at extra expense and with extra concerns regarding water resistance.

The ugly: Gambrel roofs can be unstable, owing to the simple, open design at the top. For this reason, gambrel roofs may not perform well in areas that receive heavy snow or may require frequent inspections.

Mansard Roof

Similar to gambrel roofs, mansard roofs have two different slopes, the lower much steeper than the upper. In fact, the upper slope of a mansard roof often appears almost flat. A mansard roof slopes on all four sides, making room for a bit more space in the upper floors.

The good: The extra space on the upper floor and the interesting look of a mansard roof are often good selling points that add visual interest to a home.

The bad: If you want to add light in the upper floor, you’ll need to add dormer windows or a garret, resulting in extra expense and the addition of more seams that can risk leaks.

The ugly: Similar to a gambrel roof, the open design with a low pitch at the top of a mansard roof results in a less sturdy roof that is particularly unsuited for areas that receive heavy snowfall.

Skillion Roof

Also referred to as a shed roof, the single-slope skillion roof is a simple roof design that used to be reserved for home additions, sheds, and lean-tos. However, skillion roofs also appear very modern with certain added design elements and have come back into favor with modern builders.

The good: Despite their relatively simple, low-cost, design, skillion roofs provide an unexpected aesthetic appeal, especially to those that like modern design. In addition, a steep pitch allows snow and rain to slide off easily.

The bad: Such a high-pitch roof can present design problems inside, with too-low ceilings on one side of the home without much visual interest.

The ugly: Though good for heavy snow areas, areas with heavy winds may present an issue for skillion roofs, which often have overhangs wind can get underneath to produce lift, and not much else to stabilize.

Sawtooth Roof

Sawtooth roofs are effectively a series of skillion roofs, pitched parallel to one another so that the overall effect resembles a saw blade. Between each pitched roof, a vertical side descends to provide separation between the roof elements. Like the skillion roof, sawtooth roofs were once used primarily in commercial buildings, but have recently experienced increased interest by builders interested in a modern aesthetic.

The good: Besides the appeal of the modern design elements, sawtooth roofs provide additional height at the upper levels of the home.

The bad: The complex structure, including multiple roofs, valleys, and additional windows, means a drastic increase in design and materials costs.

The ugly: Valleys and other seams provide an excellent place for rain and snow to gather, putting your roof at risk for leakage.

Curved Roof

A curved roof is exactly what it sounds like – a large expanse of curved rooftop. Most curved roofs are simple and resemble a curved skillion roof. However, the options are endless for curved roofs of various heights and sizes on a single Rhode Island home. Often, curves are placed to highlight window features, entrances, or walkways.

The good: Curved roofs provide a unique aesthetic appeal not offered by any of the more traditional roof types.

The bad: Roofs with a shallow curve allow water and snow to run off, but not as effectively as other roof types with much steeper pitches.

The ugly: Depending on their complexity, curved roofs can be expensive to design and build.

Which type of roof is right for your home? That question depends on several factors. If you are building a new home or completely renovating an older home, will you be living in an area with a homeowners association (HOA)? If so, many HOA covenants dictate the roof styles acceptable in your neighborhood. Otherwise, you’ll need to consider whether your ideal roof type will stand up to any wind or snow in your area, as well as whether it supports the roofing material you prefer.

If you are re-roofing or renovating an existing home, take a look at the roof type you have currently. Some roof types, such as mansard, gable, and hip roofs, are easy to add additions of any roof type to. Others are more difficult. Most of the time, however, unless you’re willing to add design elements or remove a portion of the existing rafters – at additional expense – you’ll experience difficulty changing up your roof type altogether.

Roof Pitch

Regardless of which style you choose for your Rhode Island, roof pitch affects the aesthetic appeal of your home as well as the way it protects your home against the elements. Pitch is described as a certain number of vertical feet over 12 feet of run; therefore, a roof with a 5:12 pitch moves 5 feet vertically with every 12 feet of rooftop and is steeper than a 3:12 roof. Pitch determines the roofing materials best suited for your roof as well as the positioning of any gutters.

Roofing Materials

Most roofing materials are fairly versatile and can work well with many of the above roof types. Asphalt shingles, metal shingles, tiles, shakes, and metal roofs are fairly commonplace on most of the more common roof types. However, the more complex your roof gets with additions of valleys, seams, gabled windows, and other features, the more risk you take regarding water leakage. Similarly, roofs with a low slope tend to collect standing water and snow, risking leakage.

For that reason, metal roofing systems are preferred for many of the more complex roof shapes, as well as for low pitch roofs 3:12 and under. In addition, curved roofs do quite well with metal, since metal can be easily shaped to cover large areas of curved roof. Metal is also preferred for the very steep portions of gambrel and mansard roofs, simply due to its durability.

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