silicone roof coating system installed over a metal roof

Silicone Roof Systems and Existing Metal Roofs (Costs, Durability, and Installation)

Greg PalyaSilicone Roof Coatings

Are you the owner or manager of a commercial building with a metal roof? Perhaps it’s leaking and/or very old and you’re wondering what cost-effective repair or restoration options you have?

If that’s true, you’ve come to the right place!

The short story is…silicone roofing systems can be installed over your existing metal roof. They eliminate the complete tear-off, make the roof seamless, provide a new 10-20-year warranty, and can reduce your future energy costs.

But there are probably more questions you have, such as:

  • Can I see some photos of silicone roof systems over metal roofs?
  • Why would a metal roof owner consider silicone roof systems?
  • How long will a silicone roof system last over a metal roof?
  • How does a silicone roof system get installed over a metal roof?
  • How long will it take to install a silicone roof system over a metal roof?
  • What happens after the installation?

And just so you’re aware, West Roofing Systems has been in commercial roofing since 1979. We specialize in spray polyurethane foam roofing, which uses silicone roof coatings for protection from UV rays. Since around 2008, using silicone roof coating systems on their own has been an attractive, low-cost option for certain situations.

Every article written at West Roofing Systems is produced in-house and is reviewed and approved by a spray foam and coating expert with more than 30 years of experience.

Can I see some photos of silicone roof systems over metal roofs?

The first thing everyone wants to see are some photos!

Here are some existing metal roofs that have been restored with silicone roof coating systems:

Schill – Bedford, OH (2021) – Before Photo

schill roof before a silicone roof coating system

Schill – After Photo

Nature’s Garden – Wellington, OH – (2021) – Before

Nature’s Garden – After

Chemtron – Avon Lake, OH (2021) – Before

Chemtron – After

You might be wondering, “why did these building owners choose to install a silicone roof system?”

Why would a metal roof owner consider a silicone roof system?

Reason #1 is cost.

The cost to install a silicone roof system is around $2-$4 per sq. ft. Variables in pricing include the length of the warranty, amount of preparation to get the roof ready to accept the coating, the location of the building, and many more.

The cost to remove all the metal panels and install new ones costs approximately $15-$20 per sq. ft.

Reason #2 is a new warranty.

If your metal roof is older, yet in still decent shape, installing a silicone coating system can get your roof under a new warranty.

It’s a great peace of mind knowing your roof is under a brand-new warranty.

Reason #3 is having a seamless roof.

A metal roof has seams, screws, etc. that penetrate the metal panels. Screws can back out; seams can rust and wear out. All these things can create opportunities for water to enter your building.

When silicone coating is installed, it’s fluid-applied.

This means the entire roof will be one solid layer.

Having a fluid-applied coating system seals up all the microscopic punctures that have been letting water in, and the heat/cool air from your building to escape.

Now that you know some of the benefits of silicone roofing systems, you’re probably wondering how long these coatings last?

How long will a silicone roof system last over a metal roof?

Typical warranties from all the top manufacturers of silicone roof coatings last 10-20-years. At West Roofing Systems, we’ve been using these coatings for more than 40 years. In 40 years, it is very, rare that these coatings don’t outlast their warranties.

It’s important to know that the thickness of the coating determines the length of the warranty.

  • For 10 years, 20 mils of coating are installed.
  • For 15 years, 25 mils of coating are installed.
  • For 20 years, 30 mils of coating are installed.

NOTE: The longer the warranty, the more coating that’s used, the higher the cost will be.

Now that you know how long these roofs will last, you’re probably wondering how they get installed?

How does a silicone roof system get installed over a metal roof?

If you think a roofing contractor shows up, sprays (or rolls) some paint-like product, and collects a check, well then, you have been mistaken.

A silicone roof system is a “roofing system”. Many steps are involved to make sure the metal roof remains leak-free throughout the warranty.

Step 1 – Clean the roof

The first step is to clean away any of the debris that could interfere with the coating’s adhesion to the metal roof.

All dirt, algae, leaves, etc. need to be removed.

This is usually done through power washing.

Step 2 – Adhesion test

Before any coating is installed, a contractor needs to make sure the coating is going to adhere correctly. An adhesion test usually involves putting some coating down, adding fibered mesh over top, letting it dry, and then installing more coating over the top of the mesh.

Once it’s dry, attempt to “lift” the mesh.

If you aren’t able to, the coating passes the adhesion test. If not, an adhesion promotor primer needs to be used.

Step 3 – Primer

A roofing contractor will inspect the condition of the metal roof to see if a rust inhibitor primer is needed. Primer is used to prevent areas to continue rusting and to help with adhesion.

Step 4 – Seam and screw head treatment

Seam treatment is very important as the seams are areas that break down the fastest on a metal roof.

When a metal roof expands and contracts, it’s the seams that take the most stress.

To give the seams and penetrations extra strength, a coat of silicone is applied, then a fibered mesh is installed into the wet coating to all horizontal seams and penetrations. Some smaller penetrations will receive silicone sealants.

A heavy coat of silicone coating is then installed over the mesh.

Screw treatment is very important to a complete the coating system. Every screw will be inspected, tightened, or replaced with new oversized screws.

Once all screws have been inspected a self-leveling silicone sealant will be applied to every screw head before the application of silicone roof coating.

Step 5 – The installation

We’re finally at a point where the roof has been prepared to accept the coating. The entire field of the roof gets silicone coating, including the seams which already have coating.

The coating is installed in two coats.

Depending on the amount of wind and the location of the building, the coating can be installed using a spray gun or by rolling.

An example installation of a 15-year warranty (25 total mils) could be:

  • 25 mils of coating over the fibered mesh at the seams
  • Pass #1 of coating is installed 13 mils thick
  • Pass #2 of coating is installed 12 mils thick

The result would be 50 mils of coating over the seams…and a total of 25 mils of coating over the field of the roof.

Now that you know how a silicone coating system is installed over a metal roof, you might be wondering how long it will take to install?

How long will it take to install a silicone roof system over a metal roof?

The length of time to install a coating system depends on:

  • How many repairs need to be completed before installation?
  • Type of corrugation of metal can be a factor.
  • How much coating is going to be installed?
  • Are the weather conditions favorable?
  • Is the roof flat, have multiple levels, lots of penetrations?

An average of 2,701 sq. ft. of the coating system was installed per day for the three projects with photos at the beginning of the article.

Now that you know how long the installation takes, you may be wondering what happens after the install?

What happens after the installation?

You might be wondering, if I get a 15-year warranty and the field of the roof is supposed to get 25 mils of coating, how do I know if it’s 15, 25, or 35 mils?

What happens with the warranty?

When the installation is complete, the manufacturer granting the warranty will measure the amount of coating on the roof.

If it’s 20 mils and it’s light, then the contractor needs to install more coating before the warranty is granted.

Once the correct millage is installed, everyone signs off on the warranty and that’s the end of the installation.

NOTE: it’s important as a building owner to understand what’s covered and what’s not covered in the warranty. For example, hail damage, animal damage, and tornado damage will not be covered in a warranty. If the drains or gutters aren’t cleaned regularly and there’s water that cannot leave the roof through the drains or gutters, damage from “ponding water” is not covered.

This is why having a routine maintenance plan is important. Having one will keep your drains and gutters clear, debris off the roof, simple repairs can be made if hail damage occurs, etc.

It’s just like changing the oil on your car, maintenance needs to happen for anything to last as long as it’s designed to.

For a 15-year warranty, 25 mils of coating will be installed over the roof. In year 15, that amount may be reduced to 7-8 mils.

This is when it’s time to schedule a recoat.

A recoat will bring the level of coating back to 25 mils and grant you a new 15-year warranty.

Are you ready to learn more about silicone roof systems?

If there’s one thing to take away from this article, it’s that you can avoid paying $15+ per sq. ft. to remove and replace your metal roof…and instead, install a coating system for much less.

There are some eligibility issues.

The seams need to be in decent shape and there has to have been consistent maintenance.

If the roof has been neglected for many years or it’s severely deteriorated, it may not be a good candidate for a coating restoration.

If you have any questions about silicone roof systems, or to see if your metal roof is eligible, you can contact West Roofing Systems at any time.

West Roofing Systems has been in commercial roofing since 1979. No matter your situation or future goals, we can develop a cost-effective solution that fits your budget.

download the silicone roof coating cheat sheet
About the Author

Greg Palya

Greg Palya is the Digital Content Manager of West Roofing Systems, Inc. He has a B.S. in Marketing from the University of Akron and an MBA in Marketing from Walsh University. When he's not trying to teach others about spray foam roofing and silicone roof coatings, you can find him on the basketball court or golf course.