The most commonly used roofing material on the market today is asphalt shingles. But there are certain situations or areas where shingles shouldn’t be installed.
One of these areas is a low slope or flat roof. Unfortunately, I still see shingles installed on a low slope roof.
Not only is this a problem for the shingles themselves, but also the warranties that protect your investment. That’s why you need to know why you shouldn't install shingles on a low slope roof.
For over 30 years, the team at Bill Ragan Roofing has helped homeowners avoid being taken advantage of with unbiased and honest information. Because of this, I’ll help you understand the “why” behind not using shingles for low slope roofing.
This article covers the following topics:
- What is considered a low slope or flat roof?
- Why shouldn’t you install shingles on a low slope or flat roof?
- Why would a roofing contractor recommend shingles on a low slope or flat roof?
What is considered a low slope or flat roof?
Roof pitch is the steepness (angle) of your roof or certain roof facets. Roof pitch is a ratio calculated by the number of inches or feet it rises vertically for every 12 inches or feet it extends horizontally.
For example, a roof with a 6/12 pitch will be 6 inches (or feet) up for every 12 inches (feet) out. With that in mind, a roof is considered low slope when the roof’s pitch is below a 2:12.
(Flat roof with membrane example)
This means your roof is low slope if its pitch is less than 2 vertical units (inches or feet) up for every 12 horizontal units out. It should be pretty obvious if your roof or a roof facet is low slope.
But if you’re unsure, don’t risk your safety by getting on your roof to measure its pitch. You’ll learn your roof’s pitch after an inspection by a local roofing contractor for your roof replacement.
Why shouldn’t you install shingles on a low slope or flat roof?
Now that you know what’s considered a low slope roof, you’re ready to learn why you shouldn’t install shingles on them. According to shingle manufacturers and/or per codes, a low slope (or flat) roof is not steep enough for shingles to be installed on it.
(Red: low slope area that shouldn't have shingles; Green: good pitch to have shingles)
The reason for this is that shingles aren’t meant to have sitting water on them. Because a low slope or flat roof isn't steep enough for water to flow down to the gutters, this leaves pools of water sitting on the shingles.
This drastically shortens an asphalt shingle's lifespan and creates a leak if there are nail pops or other problems in the area. No matter what, shingles shouldn’t be installed on anything less than a 2:12 pitch.
Not only will this result in problems, but the manufacturer also won’t warranty the area because the installation instructions weren’t followed.
Why would a roofing contractor recommend installing shingles on a low slope or flat roof?
Now you know why you shouldn’t install shingles on a low slope or flat roof. But why would you consider doing this in the first place?
Most of the time it’s because a roofing contractor recommends it. This could be a mistake or lack of knowledge, but it’s not usually done by accident.
If a roofing contractor is willing to install shingles on a low slope or flat roof, it’s most likely to lower their prices to win your business. Not only is this a shady sales tactic, but it’s also a huge red flag when comparing multiple estimates.
For example, installing a membrane roof system on a low slope or flat roof costs around $12.00 to $17.00 per square foot. For comparison, it’ll cost around $6.00 per square foot for architectural asphalt shingles.
This is a big difference in price between the two roofing materials. So, it can be tempting to go with the cheaper overall price.
But if you install asphalt shingles on a flat or low slope roof, you’ll actually end up spending more money in the long run. I understand pricing is a huge decision-making factor for most homeowners.
However, you’re setting your investment up for failure by going with the roofing contractor who recommends installing asphalt shingles on a low slope or flat roof to win your business.
What are the best roofing materials for a low slope or flat roof?
After reading this article, you know why you shouldn’t install shingles on a low slope or flat roof. You also know to look out for a roofing contractor trying to lower their prices by installing shingles instead of a flat roofing material.
But if you can’t use the most common roofing material option on the market for a low slope or flat roof, what can you use? To answer this question, I wrote another article breaking down the best low slope roofing materials.
For over 30 years, the team at Bill Ragan Roofing has provided low slope and flat roofing services to thousands of homeowners in Nashville and surrounding Middle Tennessee areas. We take pride in our workmanship and back it up with a lifetime craftsmanship guarantee.
Check out The 4 Best Materials for a Flat Roof (& How Much They Cost) to find the right roofing material for your flat or low slope roof replacement.
