Blog

How Does a Metal Retrofit Roof Become Flat?

Have you ever looked at your commercial metal roof and wondered, “How can something with ribs and bumps become a flat, leak-free roofing system?”  
 
At Weather Shield Roofing Systems™, we’ve been helping businesses with this exact question for over 40 years. And we get it: roofing retrofits can feel confusing, especially when it seems like there’s no way to go from corrugated and bumpy to clean and smooth without a complete tear-off. Let’s clear that up. 

“How does a metal roof become flat?” 

This is probably the #1 question we hear when talking about metal retrofit roofing. And it makes perfect sense. When you look at a standing seam or corrugated metal roof, it’s full of ridges, panels, fasteners — all the stuff that looks nothing like a traditional flat roof. 

The key to flattening a metal roof lies in insulation and layering. 

Here’s how we do it: 

1. Insulation is installed between the metal ribs — and it’s not just any insulation. We use insulation that’s thick enough to rise above the highest rib by at least an inch. 

• Example: If the ribs are 2 inches tall, we install 3 inches of insulation. Why the extra inch? To create solid support so that when someone walks on it, the insulation doesn’t compress or crack over those ribs. 

1. The insulation is mechanically fastened into the metal deck below, tying it securely into the building’s structure. This step is crucial to create a stable, flat surface — not just something that sits loosely on top of the ribs. 

1. A new roofing membrane — usually TPO — is installed on top, also mechanically fastened right through the insulation and into the metal deck. This membrane becomes your new flat roof surface. It’s tough, flexible, and designed to last for decades with proper maintenance. 

From the outside, the finished result doesn’t look like a patched-up metal roof at all. It looks like a clean, seamless, flat roofing system — because that’s exactly what it becomes. 

“Do you have to remove the old metal roof first?” 

Another major concern we hear is: “Aren’t you supposed to remove all the metal first?” 

Actually, no. That’s one of the biggest misconceptions. 

Many property managers assume re-roofing means exposing the building to the sky, ripping off large metal panels, and bringing everything down to the structure. But that’s not necessary — and thank goodness, because that approach can triple your roofing cost.  
Instead, with a metal retrofit, we leave the original metal roof in place. We use it as the foundation, fastening everything right over it. This avoids the mess, risk, and cost of a full tear-off while still giving you a watertight, long-term solution. 

“What will it look like when it’s done?” 

Visually, it will look just like any other commercial flat roof. Smooth, white (or gray depending on your material choice), clean lines, and no exposed screws or ribs. And because the system is built to flex with your building, it can handle seasonal expansion and contraction without failing. 

One of our favorite ways to explain this is with before-and-after photos taken throughout the roofing process. Seeing the transformation helps everything click. We’ve documented projects like LEITZ Tooling that show the roof going from a bumpy metal surface to a fully flat membrane system. It’s a game changer when customers see the step-by-step visuals. 

“Why would someone choose this over just coating the roof?” 

Great question — and an important one. 

Roof coatings are sometimes marketed as a cheaper fix for metal roofs. But here’s the honest truth: coatings are fine for small spot repairs or sealing specific areas like around a pipe or curb. But for widespread issues? Not recommended. 

Coatings tend to flake, chip, and spider-crack over time. This not only looks bad — it also makes it nearly impossible to track leaks. Instead of a single failure point, you end up with a hundred micro-cracks and no clear idea where water is getting in. 

At Weather Shield, we don’t recommend full-roof coatings on metal systems because they just don’t hold up long-term. Yes, coatings may be half the price up front. But in a few years when leaks come back and you’re paying again (sometimes more), that “cheap” fix becomes an expensive lesson. 

“Are there any other benefits to this system?” 

Absolutely. One hidden advantage of the metal retrofit system is added insulation value — or “R-value.” 

Metal buildings typically have bat insulation tucked underneath the roof deck. With our retrofit system, you’re adding another layer of insulation on top of the metal roof, essentially sandwiching the metal between two layers of thermal protection. 

We’re not necessarily adding insulation to meet code (though it often helps). The primary goal is to flatten the roof — but you get better energy performance as a bonus. That means: 

• Reduced heat gain in the summer 

• Lower heating costs in the winter 

• And more comfort inside your building, year-round 

Another major benefit is perimeter leak protection. Older metal roofs are prone to ice damming at the edges. Ice builds up, creeps under the edge, and causes water to leak into the building. Our new membrane systems go up and over the edge — sealing the perimeter tightly and preventing that kind of intrusion. It’s like wrapping your roof with a protective barrier that water can’t work its way under. 

So, is a metal retrofit right for your roof? 

If your metal roof is 20–30 years old, showing signs of leaking, or causing maintenance headaches year after year — a retrofit might be your best long-term option. It: 

• Avoids a costly tear-off 

• Provides a brand-new, fully watertight surface 

• Reduces future maintenance 

• Adds R-value 

• Improves energy efficiency 

• Extends the life of your roof for decades 

At Weather Shield Roofing Systems™, we specialize in this kind of transformation. Our goal isn’t just to stop leaks — it’s to provide you with a smart, cost-effective roofing solution that lasts. And if you ever want to see real-world examples, we’re happy to walk you through photos of recent jobs and explain every step in simple terms. 

 
If you’re considering a metal roof retrofit and have more questions, we’re here to help. Reach out anytime — no pressure, just honest answers from people who’ve been doing this for over 40 years.