People have different ideas of what they think a steep roof pitch is. But OSHA states that a steep roof has a rise-to-run ratio of 4:12 or more and an angle of at least 18.43°.
Therefore, any roof pitch with a rise-to-run ratio lower than 4:12 results in low-sloped roofs. However, some types of architectural designs call for a dramatic pitched roof. In such cases, the roof slope is steeper than usual. And that applies to anything with a rise to run ratio of 12:12 and an angle of 45° or more.
It helps to understand how roof pitches are determined, factors to consider when choosing steep roofs, their pros and cons, and what various rise-to-run ratios mean. And this article discusses all these things in detail to help you determine how steep your roof should be.
How Do You Measure Roof Pitch?
Any roof pitch with an angle of 18.43° or a rise-to-run ratio of 4:12 or more qualifies as a steep roof. But what does it all mean?
Typically, a roof pitch refers to how steep it is. And the slope is measured in the ratio of inches rise per horizontal foot (or the metric equivalent). You can also refer to the pitch as a roof’s vertical rise over horizontal run/span.
So long as a roof is not flat, it also forms an angle of deviation from the horizontal plane. So a ratio of 4:12, which is the beginning point for steep roofs, means the roof rises 4 inches per 12 inches span. And that translates into the 18.43° threshold.
Roof pitches are traditionally measured as vertical rise over horizontal run, where the run is always 12” (12 inches). The number 12 comes into play because 12 inches make up one foot.
So, a roof with a 6/12 slope is a steep roof (26.57 °). However, one with a pitch of 8/12 (33.69 °) is more vertical. A roof with a 10/12 slope (39.81 °) is the steepest of the three. And any roof with 12:12 (45 °) pitch has entered the dramatic pitched-roof territory.
It is also worth noting that while flat roofs seem completely horizontal, they may not always be. Some flat roofs have a minimum pitch of 0.25:12 for drainage purposes. However, others have a slope of 0/12, translating to 0° or 180°.
Factors That Determine a Roof’s Steepness
There is nothing wrong with wanting a steep roof. However, several factors influence how steep your roof slope should be. Below are some of the critical things to consider when choosing a roof slope.
1. Your Geographical Region
Where you live will largely determine how steep your roof will be due to the area’s climate. In areas of heavy snow, winds, and high rainfall, steeper roofs ensure that precipitation drains quickly, helping to safeguard their integrity.
For example, in cold and temperate climates of Northern Europe and America, you will notice plenty of steep gabled roofs. These roofs have steep pitches to help drain the snow or rain that hits the rooftop regularly.
Generally, if you live in an area where drainage will be an issue, you may want to consider a steeper roof pitch than usual. However, bear in mind that some types of steep roofs may require additional support against strong winds.
2. Local Building Codes
Your local building codes have a role to play in determining how steep the roof pitch is for high-sloped roofs. And these codes will likely factor in your climate, the architectural design, and the roofing materials when regulating how you should build.
For example, in areas like New York or Chicago, which are known for their abundance of snow, don’t be surprised to learn that experts would recommend steeper roofs to improve performance.
On the other hand, flat or low-sloped rooftops would be more desirable in arid areas, such as the Arizona desert, since there is little precipitation to worry about anyway.
3. Architectural Property Design
The architectural property design you prefer will influence your roof pitch to a significant degree. That’s because roof shapes and slope designs partly define some types of architecture.
Generally, Elizabethan and Gothic house designs tend to offer drama. For Elizabethan homes, it is typical for the rafters (rise) to be longer than the span (run), thus putting these homes in the dramatic pitched roof category since they have angles of more than 45°(e.g., 16:12).
Tudor homes are also defined similarly by very steep gable roofs. It is common to find rooftops with pitches of anywhere from 10:12 to 14:12 on such properties.
On the other hand, Gothic architectural designs have a rise usually equal to the run (e.g., 12:12), thus putting their roof pitches at 45°.
Some Roman homes are also steep. The general rule of thumb is to have rafter lengths that are one-third of the span. So, they can meet the 4:12 steep roof pitch threshold. However, some fall below that.
4. Your Building and Renovation Budget
The steeper you want your roof to be, the more money you should prepare to pay to build and renovate it.
The steeper the roof, the more safety measures you need to take to safeguard anyone who installs or replaces it. These include guardrail systems with toe boards, personal fall arrest systems, and safety net systems.
Workers require these measures on very steep roofs because the more significant incline angle makes it harder to work on. And they are more likely to fall and injure themselves. Also, their tools and debris are likely to slide from the roof and harm those beneath.
However, putting those safety measures in place tends to come at a price. You would need to spend more on them, whether installing the roof for the first time or repairing and replacing some of its components during renovation.
And that’s not the only challenge. Most times, the constriction contractors must put their roofing components together on the ground. Handling something simple like a bundle of shingles becomes difficult since there is limited space to temporarily store them on the roof surface as contractors install them. And the steep incline makes it harder to carry many things at once because it requires extra endurance.
So, due to the logistical challenges, you may spend more on equipment to carry roofing parts and labor since contractors would take longer to do their job. Again, you will be the one paying for everything.
For these reasons, steep roofs tend to be more expensive than flat or low-sloped roofs. So, it would help if you had enough money in your budget to accommodate the issues that will come up during installation or repair.
5. Your Preferred Roofing Materials
You can use various roofing materials on a steep slope. However, others are much more suitable for low-sloped or flat roofs.
Your biggest obstacle will be your local building codes and what they state concerning the roofing material you want to install. If you do not stick to the regulations, you may pay heavily for that in the future. And if you wish to use a particular roofing material, you may either have to change your roof’s incline, use additional materials, or opt for a less desirable alternative.
Wood, metal, slate, concrete, clay, asphalt, wood shake, shingle systems, and mineral-surfaced roofing are suitable for a steep roof pitch. You can install them on roofs with slopes of 4:12 or more.
However, some roofs may require a double synthetic underlayment application to improve their performance. And roofing materials like some EPDM and TPO membrane assemblies are unsuitable for installation on roof slopes exceeding ½: 12. So, you cannot use them on a steep roof.
The texture of your roofing materials also matters considerably. Smooth textured roofing like metal tiles is excellent for the low-sloped roof because the precipitation slides off easily.
However, excessively smooth rooftops can be problematic if you choose a steep roof with an average pitch of 4:12 to 6:12 in areas of heavy precipitation. In such cases, you need textured roofing materials that can hold the snow and moderate the amount that the roof sheds at any one point to prevent injuries and death of those passing or standing underneath.
For roofs with a pitch greater than 6:12, it would be best if you configured your roof design to prevent shedding on high-traffic areas to enhance safety in case of heavy snowfall. The last thing you want is for your loved one to die in a snow avalanche generated by your roof.
6. The Roof’s Functionality
It would be best to consider the functionality of your roof before you settle on its steepness. The lower the roof slope, the easier it is to install something that lies on the surface for a prolonged period.
For example, if you want to install solar panels, you would be better off with a low sloped or flat roof. You can easily install and maintain such panels. And if you want to take advantage of sunlight coming from a particular direction, you can have the panels tilted.
On the other hand, solar panels perform best when tilted at angles of 30°or slightly more. And steeper roofs with pitches higher than 40° are less than ideal for solar panels.
So, while you could get some sunlight from one direction, the steeper roof sections may block sun rays from the opposite direction as the day goes by. When that happens, your solar panels will not store as much energy as they should and, thus, perform dismally.
In addition, it is much harder to install and maintain solar panels on a steeper roof because it has to defy the force of gravity. Also, your panels may not get the optimum sunrays. And you may require more equipment and resources to keep the panels in place.
However, while solar panels may not suit dramatic pitched roofs, they could work very well for water harvesting. They tend to shed water quickly and reduce the likelihood of it becoming contaminated, unlike flatter roofs. So, you will end up with cleaner water much faster, even if the rainfall amounts are low.
7. The Manufacturer’s Warranty
Roofs have an average warranty of about two or so decades, during which contractors will repair them for free or at a reduced cost. However, your ability to enjoy the warranty depends on whether you followed the installation instructions to the letter.
Many manufacturers specify the minimum roof pitch for their products. And it would be best if you remembered that the threshold they set might be more than the minimum roofing slope requirements your building codes state.
Suppose you do not follow the steepness guidelines. In that case, you may void your roofing warranty, which would make you liable for any roofing failure and its subsequent repair or replacement even before the warranty period is complete.
Pros and Cons of a Steep Roof Pitch
Steep roof pitches have their fair share of pros and cons. Below are some of them.
Pros of Steep Roofs
The following are some of the advantages of installing steep roofs on your home:
- Steep roofs shed water quickly, thus providing an excellent catchment area for water harvesting, thus reducing your water bills.
- Roofs with steep pitches drain well, which reduces water damage to their surface, thus extending their lifespan. In addition, they will require less maintenance.
- The steeper the roof, the more space it creates underneath, extending your usable space in the home.
- Steep roofs can withstand strong winds and the elements pretty well, allowing them to withstand Mother Nature’s wrath.
- The attic space underneath steep roofs provides improved ventilation and reduces energy costs in your home.
- Steep roofs can be a way to make a dramatic impression on people because they are apparent and remarkable.
Cons of Steep Roofs
While steep roofs offer many benefits, they also have some disadvantages worth remembering.
- It is much harder to install or renovate steep roofs. They pose a danger to your safety or that of your contractors.
- Due to the logistical challenges of dealing with roofs with steep pitches, you will spend more installing or repairing them.
- On a steeper roof, you would have less utility space to do other things, such as creating additional outdoor space on the rooftop.
- When steep slopes shed debris, it falls on the gutter system or the ground. So, you will have to clean your gutters or lawn regularly.
When Should You Opt For a Steep Roof Pitch?
Some circumstances require you to prioritize a steep roof pitch over a flat or low-sloped roof.
Generally, it makes sense to opt for a steep roof pitch if you want a dramatic house with improved roof drainage for water harvesting and minimal water damage. Also, consider a highly sloped roof if you opted for architectural designs that call for a higher rise-to-run ratio like Tudor designs. In addition, you could prioritize a steep roof pitch if you have a big budget for your roof and do not mind the work that goes into providing the drama.
Steep roofs also come in handy if you want to maintain your warranty as long as possible or require additional space for storage or other things.
Both low-sloped and steep roofs have their place. However, steeper roofs tend to offer many aesthetic and functional benefits worth considering. And it would be best for you to select a steep roof, depending on your preferences and how practical it is for your property.
If you have an adequate budget, you can get one of the steepest roofs around. And if nothing else, it is likely to make a lasting first impression on everyone who sees your home. It is unlikely that you would ever have to worry too much about curb appeal.