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If you’re shopping around for alternative roofing materials to shingles, you’ll probably come across corrugated roofing panels. However, there are often flat counterparts, making you wonder which option is the best.

What Are Corrugated Roofing Sheets?

Corrugated roofing sheets have a wavy texture. From far away, they may look as though they’re striped. But when you look at them closely, you’ll see that one piece of material is shaped with undulating curves that span the length of the sheet.

Some materials have boxier ridges than others. In the roofing industry, these may not be labeled “corrugated.” Instead, some experts refer to this shape as “ridged.” However, ridges and grooves with squared-off corners have similar benefits and disadvantages as S-shaped corrugated roofing sheets.

What Materials Do Corrugated Roofing Panels Come In?

Not all roofing materials are corrugated. However, large panels tend to be. The most common types of corrugated roofing panels that you’ll find are made of:

  • Fiber cement –  A safer alternative to cement-asbestos roofing
  • Fiberglass – A lightweight, translucent material that is often used for porch or pergola roofing because it lets the light in while protecting against rain
  • Cardboard-cement – This roofing product is designed to look like clay tiles and comes in a wide variety of colors
  • Metal – Made of pressed aluminum, iron or steel, corrugated metal roofing panels are durable and long-lasting
  • Polycarbonate – Virtually unbreakable plastic that is lightweight and often translucent


7 Reasons for Corrugated Roofing Sheets

There are several reasons to answer the question, “Why are roofing sheets corrugated?” Understanding these factors will help you make the best decision when choosing a covering for your home, outbuilding, porch, deck or pergola.

Added Strength

Take a flat sheet of paper, and wave it around in the air. Notice how it bends and curls fairly easily. It feels flexible and floppy. 

Now, fold the paper like an accordion. Try to wave it in the air again. Now, it’s more rigid and maintains a relatively flat shape.

This illustrates how corrugation strengthens roofing materials. Corrugated roofing sheets are less likely than flat ones to bend under pressure. 

This means that they resist sagging when they cover the large expanse of a roof. This is especially important when you’re dealing with snow or ice accumulation. Plus, corrugated panels won’t bend or crease while you’re moving or storing them. 

Enhanced Drainage

When it rains, water always makes its way to the lowest point on a surface. If you have a flat roof, any indentation will collect water, creating unequal pressure on the surface of the roof. This can lead to sagging, wet spots, moisture damage and roof cave-ins. 

The corrugated valleys on a roofing panel are evenly spaced. Therefore, they distribute the weight of rainwater equally across the roof. These channels also act like narrow gutters, directing the water where you want it to go. Combined with an adequate drainage system, you can avoid moisture damage and safeguard the structure of your home by using corrugated roofing sheets.

Reduced Cracking or Warping

Warm temperatures cause roofing materials to expand, while cold temperatures lead to contraction. Your roof is particularly vulnerable to extreme changes in temperature because of its location. As the sun beats down on it, it expands, and it shrinks at night when the temperature drops. 

A flat roofing panel that’s fastened securely doesn’t allow for as much freedom of movement as a corrugated sheet. The waves in the corrugated sheet let the material shift without affecting the position of the fasteners. Therefore, it’s less likely to crack or develop wear than a flat roofing panel.

Less Leakage

You might be surprised by the amount of water that can trickle into a tiny hole. Although roofers take measures to seal your home tightly and prevent leaks, they have to create holes in the material every time they insert a fastener. 

With corrugated roofing sheets, the holes are created in the peak of the crown, where water doesn’t collect. Therefore, you’re less likely to experience leaks from these spots.

Hide Imperfections

Panel roofs often have exposed fasteners. On a flat roof, the fasteners may be obvious because they interrupt the smooth surface. However, the lines on a corrugated roof distract the eye from imperfections. Therefore, you’re less likely to notice the fasteners or other blemishes on the surface that may detract from the building’s curb appeal.

You should note that standing seam metal roof panels are often designed with an alternative fastening system. If you don’t like the look of visible fasteners and want a flat panel roof, you can use a product that uses a series of clips instead of screws for installation.


You don’t have to limit corrugated roofing panels to the top of your structure. They can be used in a variety of ways, including as walls, for fencing or for collecting rainwater without gutters.

Ease of Installation

You don’t need special skills to install a corrugated metal roof. On the other hand, installing a roof with flat panels or standing seams requires a more complex skillset. In many cases, you can install a corrugated roof over existing asphalt shingles, which is not a possibility with flatter panels.

Pros and Cons of Flat Roofing Sheets

When you’re comparing flat roofing sheets with corrugated ones, you’ll likely find that there are more disadvantages than advantages. Some of the most common problems that are associated with flat roof panels include:

  • Warping – Flat roofing sheets are susceptible to warping. In fact, even new sheets may have a slight bend or bulge to them. If you gaze at a flat roofing panel with your eye level with the surface, you’ll likely notice this. The warped appearance gets worse over time as the material settles, expands and contracts.
  • Shows damage easily – When flying debris, like a falling branch or hail, hits a flat roof, it’s likely to make a mark.  The flat surface doesn’t resist damage like a stiff corrugated one would. Multiple dents on a flat roof can look unsightly and lead to further damage down the road.
  • Noisy – Flat roofing panels often make noise as they expand and contract. You might hear popping noises in the early morning or evenings as the material adjusts to the current temperature.

Should You Use Flat Or Corrugated Roofing Sheets?

Corrugated roofing sheets are ideal for do-it-yourself projects, longevity and money savings. However, they’re not recommended for every roof. Your roof must have a slope of 3 to 12 inches to benefit from a corrugated roof. This type of roofing is not suggested for flat roofs.

If you have room in your budget and want to minimize the potential for leaks, you might not opt for the exposed-fastener system that is necessary for a corrugated roof. In that case, you might look for a flat panel system with hidden fasteners or choose a different roofing material altogether.

Finally, check the gauge of the roofing material before you make a selection. Corrugated metal roofs come in thinner gauges than standing seam panels, which need to be thicker because their shape is not self-supporting. 

Ultimately, an experienced roofer will be able to guide you through the process of selecting a roof. Choosing the right option now will provide you with protection for years to come.