Roof Types

Roof Types archives for the Interstate Roofing Blog, we serve the Portland & Vancouver metro areas with residential, commercial, repair call 503 684-5611

Low Roof Pitch Options for Your Building

A roof has a “low pitch” if it slopes anywhere from 2/12 to 4/12 inches—meaning that for every foot the roof extends horizontally, the level of the roof rises two to four vertical inches. Some roofs have extremely low slopes and appear to be nearly flat. No roof, of course, should actually be completely flat. If it is, puddles of water will accumulate on the roof and ultimately damage it.

Low-slope roofs are seen on both commercial and residential buildings, although they are primarily associated with businesses. There is a reason for this: in commercial buildings, it is generally considered more prudent to maximize the use of space, leading to a flatter roof. Residential homes, on the other hand, tend to have a much steeper incline for cosmetic reasons.

Regardless of whether you’re looking for low roof pitch options for your home or your place of business, you’ll need to consider what materials are best. In this article, we’ll take a look at the choices available to you and other variables to consider when putting in a roof.

The Trouble with Low Roof Pitch

The primary advantage of a low roof pitch is maximizing space. It will allow you to utilize the space in your area all the way up to the top. This can create a number of advantages. Heating and cooling are easier in a building with a flatter roof, for example. However, low-slope roofs come with disadvantages that don’t trouble steeper roofs. The primary problem with a low slope has to do with drainage: water damages roofs, and water can begin to pool on a roof with too low of a slope. Ice and snow can also be a problem, depending on the climate. If water accumulates on your roof and can’t drain properly, it will eventually cause decay.

Direct sunlight can be another problem for a low-pitch roof, although this is certainly not an issue unique to these types of roofs. In fact, ultraviolet light can do a number on any type of roof, unless the proper materials are used.

This brings us to the primary disadvantage of a low slope roof: you are somewhat limited in the materials you can use to construct them. This is because of the importance of waterproofing. On a roof with a higher pitch, water will easily roll off, and that means you don’t need to concern yourself as much with waterproof materials. A low-pitch roof, on the other hand, absolutely must be waterproofed.

Waterproofing

Low-pitch roofs are usually waterproofed through the use of a roof membrane, which can be made from synthetic rubber, a thermoplastic such as PVC, or modified bitumen. Any of these materials can effectively carry water off the roof without allowing it to pool anywhere or penetrate vulnerable areas and cause damage. Occasionally, asphalt roofing systems are also still in use, and while these types of roofs were extremely common in the past, they’ve largely been supplanted by synthetic membranes. This is because asphalt roofs don’t seal as effectively as other membranes do.

Types of Low-Pitch Roofs

There are several options when having a low-pitch roof installed for your building. These options, however, are more limited than those for a gable roof or other higher-pitch roof. Even so, there are several choices you can make as far as the construction of your roof, each with its own set of pros and cons.

Shingles

Asphalt shingles are, as their name suggests, shingles made from asphalt and layered on your roof over felt, a synthetic underlayment, or thicker “ice and water shield”–type membrane. Shingles can be a controversial option for a low-slope roof. Most manufacturers allow shingles on slopes of 2/12 and greater, but most roofing contractors insist on greater slopes, as shingles aren’t “waterproof” but water shedding. Shingles are popular primarily because of their relatively low cost, ease of installation, and aesthetic benefits. However, installing shingles on a low-slope roof might be asking for problems. Consult a professional roofing contractor with many years of experience.

Single-Ply Membranes

Unlike with other roofing systems, where the material is built up over the membrane or layered on top of other materials, single-ply membranes are installed without the help of other layers. A thermoset or thermoplastic membrane is laid across the surface of the roof (generally over rigid insulation) and hot-air welded together. The most popular materials for single-ply membranes are PVC and TPO, which are usually reinforced with the addition of polyester or fiberglass. Single-ply membranes are a great, relatively inexpensive option that’s easy to install. However, because they’re only one layer, maintenance is critical.

Torch Down Roofing

This roofing system is made from sheets of modified bitumen—a hydrocarbon-based material—which is then sealed to the surface of the roof through the use of a handheld propane torch. The seams of the bitumen will melt and fuse together as a result of the welding process, creating seams that are completely waterproof.

This roofing material is great if you live in a particularly harsh climate. While other materials may expand or contract if the weather is hot or cold, modified bitumen will not. This material also has a long life span and is easy to repair, though it can be extremely difficult to install due to the use of the torch. As most of the roof decks in the Pacific Northwest are made of wood, the risk of fire should be a significant consideration. Only use a contractor with the CERTA certification.

Coated Roofs

For commercial buildings, one of the other popular low-pitch roof options is coated metal. Metal roofs aren’t waterproof in and of themselves, but they can be treated with a coating that makes them so. This coating helps reduce the instances of rust, increasing the life span of the roof. Generally, the coating that’s applied is a fluoropolymer paint, which allows the metal roof to become resistant to water and ultraviolet radiation. This option, of course, isn’t practical for commercial buildings that don’t have metal roofs.

If you’d like to discuss roofing options for your building, contact the professionals at Interstate Roofing. We’ve been serving Pacific Northwest for over 20 years and are always ready to share our expertise.

Do Roof Pitch Styles Affect Material Options or Installation?

Upgrading your roof isn’t something you do every day. Depending on the roof materials you select, you might only invest in a new roof once in a lifetime.

That makes your roof selection an important process.

For many homeowners, the process starts by looking at materials or color. And while both of those are important to create curb appeal, the final selection also depends on your home’s style.

You have many choices when it comes to roofing material selection: asphalt, composite, wood shake, rubber, tile, metal, and more. But it’s more than an economic or color decision; it also depends on roof pitch styles or the slope of the roof of your home.

What is pitch?

Pitch is the term used in the roofing industry to describe the angle or slope of your roof. Roof pitch is comprised of two numbers in the form of a ratio. You’ll see it expressed either with a slash – 5/12 or 8/12 – or with a colon – 5:12 or 8:12. Either way, the numerator and denominator work together to tell you the pitch of the roof.

The numerator refers to the height of the roof.

The denominator refers to the length measurement of the roof.

To keep everything relatable, the industry will always rank with a denominator of 12. Therefore a roof pitch will always be referred to as how much rise there is in the roof over a 12 unit horizontal distance.

For the roof pitch styles from above, for example, the 5/12 means that for every 12 horizontal feet of change, the roof rises 5 feet vertically. For the 8/12, it moves 8 feet in vertical rise for every 12 feet of horizontal space.

With most homes, roof pitch styles range from 4/12 to 8/12, with the lower being a moderate rise and 8/12 being a fairly steep ratio. But roof pitch can have a lot more variation.

A 1/2/12 roof would be almost flat. You might find a low pitched roof on a modern home where the slope is barely there; just enough to allow water to flow. A 12/12 roof would slope at a 45-degree angle. Old Victorian homes often have sharply angled roofs with a steep pitch and, in some cases, they can even move beyond the 12/12 ratio.

Why roof pitch is important?

The roof pitch is important for two reasons.

One, in order to estimate correctly for the amount of material needed for the job, you must have an accurate measurement of the pitch of the roof.

Two, not all materials are suited for the roof. By knowing the pitch, you’ll have a better understanding of the roofing materials that will work best on your home over time.

When a roof is perfectly flat, the calculation for materials is simple: width times length.

As a roof rises, the different pitches require more material to compensate for the slope. The industry has tables for slope factor based on the angles of your home to help determine the extra materials needed. In our examples above, a 5/12 pitch would have a slope factor of 1.085. Use this to multiply with your answer from width times length and you’ll have an accurate measurement of how much material you’ll need.

Roof shapes have evolved over time. Head back hundreds or even thousands of years and you’ll find roofs were made from very simple materials. Straw, mud, grass, wood – only gradually did they start learning the benefits of using different materials and to gently slope the roof for protection.

Flat roofs make sense on some structures. But if you make it perfectly flat, water has nowhere to go. Even a gentle slope is needed for proper drainage. Angles help control the elements and give a building style. But no matter how much you like a particular material, some homes simply aren’t meant for some types of roofs.

Roof Pitch Styles

Low Pitch – these are the safest roofs. They are easy to walk around on and easy to perform maintenance. But they are also more prone to leaks and require more frequent inspections. That’s why you won’t find a lot of low pitched roofs where weather is extreme – both water and snow buildup can be detrimental and put a building at risk. Low pitch is usually the design of choice on modern, sleek, contemporary homes.

Flat roofs cannot be covered with traditional materials such as shakes or asphalt shingles since there isn’t enough pitch to combat damage from wind. Flat roofs are limited to more commercial-grade roofing applications, such as tar and gravel, rubber, or roll roofing.

Medium Pitch – this is where most home roofing systems lie. A medium-pitch gives you ample choices in materials while providing enough slope to keep rain and snow from accumulating on the roof. While it still needs periodic inspections, this is where most roofing choices exist.

If you prefer clay or cement tiles, they can be installed on roof pitches from 2.5/12 up to 20/12. However, for flatter roofs 2.5/12 to 4/12, it is recommended that they are installed with an underlayment to handle the extra weight.

A vast amount of the choices fall into the 4/12 to 20/12 range. This is where asphalt or composite shingles are, which are the most popular types of roofing options on the market today.

If you like the look of wood or slate shingles, they need a more gentle sloping roof, with roof pitches in the 5/12 to 12/12 angles working best.

High Pitch – these are the most expensive roofs to install, but also give dramatic architectural elements. A contractor cannot work on a high pitch slope without safety gear, so more cost will go into it for both repairs and renovation.

Other Considerations

Your final selection will also determine which warranties are in place and how long your roofing materials will last. Be sure to ask about both material and workmanship warranties as the two are often separate.

If green building is important, roof pitch can impact your final selection. Consider both the shingle material and any underlayment necessary to complete the job.

Also investigate fire ratings for the different types of roof pitch styles, especially if you are in an at-risk area.

So what type of house do you currently own? What type of roofing are you interested in? Knowing the roof pitch plays an important part in the selection process; what questions can we answer to help you make your final selection?