Silicone Roof Coating for Commercial Roofs: How It Works and When It Fits
A silicone roof coating is a fluid-applied system that cures into one seamless membrane over an existing flat or low-slope commercial roof, restoring it without a tear-off. For a building owner or facility manager looking up at an aging roof, that can mean years of added service while the building stays open and the old roofing stays out of the dumpster. It also raises two fair questions. How does the system work once it is on the roof? And which roofs is it right for? This post answers both, from the chemistry of the coating and the steps of an installation to the trade-offs, the comparison with replacement, and how a silicone roof handles a Michigan year. It is written for commercial buildings: the warehouses, plants, offices, schools and retail centers where flat roofs are the norm.
What a Silicone Roof Coating Is and How It Works
Silicone is an inorganic material built on a backbone of silicon and oxygen. That chemistry is the reason it stands up to sunlight and weather for so long. A silicone roof coating is also a moisture-cure product. Once it is spread across the roof, it reacts with the humidity in the air and turns from a liquid into a solid, rubbery film. After that film has cured, it does not absorb water.
Most silicone used on commercial roofs today is high-solids. Very little of what comes out of the pail evaporates as it cures, so nearly all of the material a crew applies stays on the roof as finished coating. Because each pass leaves more coating behind, the roof reaches its specified thickness in fewer passes, and fewer passes mean a shorter job.
Once cured, the coating forms a monolithic membrane. It is one continuous sheet across the roof, with no laps or joints for water to work into. It also stays flexible. A flat roof grows in the afternoon sun and shrinks on a cold night, and the silicone stretches and recovers with it, so the seams and edges where older roofs tend to open up stay sealed.
Acrylic is the other common elastomeric coating, and the biggest difference between the two shows up where water stands. Acrylic is water-based and does its best work on roofs with positive drainage that dry out after a rain. Cured silicone keeps its film intact under standing water, so on a roof with chronic ponding it is usually the stronger choice. Our post on the benefits of commercial roof coating systems compares acrylic and silicone side by side in more detail.
Which Commercial Roofs Can Take a Silicone Coating
Silicone bonds to a wide range of roof types. It goes over metal roofs, modified bitumen, built-up roofing, single-ply membranes such as EPDM and TPO, spray polyurethane foam and concrete decks. Each of these surfaces needs its own preparation. Metal roofs need rust treated and fasteners addressed, modified bitumen may need loose granules and splits handled, and single-ply roofs need their seams checked closely. With the right prep, a commercial silicone roof coating can restore almost any of them.
The material of the roof matters less than its condition. A good candidate is structurally sound, with a deck that is solid underfoot. A coating seals in whatever moisture is already trapped below it, so the insulation underneath has to be mostly dry. The coating can also only hold as well as the surface it sits on, so the existing membrane needs to be well bonded to the roof.
That is why an inspection and an adhesion test come before any recommendation. The inspection looks at the deck, drains, flashings, seams, penetrations and past repairs, and it checks for wet insulation. The adhesion test confirms that the silicone will grip this particular surface after it has been cleaned, and it shows which preparation that surface needs.
Timing matters too. Coating works best on a roof that is aging but still doing its job. Once a membrane has reached the end of its service life, with widespread leaks, soaked insulation and seams letting go, there is no longer a sound surface left to restore. Owners who look at coating a few years before that point keep the most options open and get the most value from the roof they already paid for.
How a Silicone Roof Coating System Is Installed
A silicone coating goes on in a set order. Each step depends on the one before it, and a skipped step usually shows up later as a blister, a peel or a leak.
Inspection and Moisture Check
The job starts with a full walk of the roof and a survey for trapped moisture. Wet insulation and damaged areas are marked so they can be cut out and replaced with dry material before anything else happens.
Repairs and Cleaning
Next come the repairs: blisters, splits, open laps and soft spots in the membrane. Then the whole roof is cleaned, usually by pressure washing, to remove dirt, oils, loose granules and anything else that would sit between the silicone and the roof. The surface has to be clean and fully dry before coating starts. Moisture-cure silicone reacts with water in the air, but water sitting under the coating keeps it from bonding to the roof.
Adhesion Testing
With the roof clean, test patches of the coating go down in several areas and are pulled after they cure. These patches show whether the silicone grips the surface as it should, and they confirm the right product and prep for that roof. Our coating system needs no primer on most roofs, which removes a full step from the process.
Detail Work at Seams, Penetrations and Drains
Most leaks start at the details, so they are sealed before the field coat goes on. Seams, fasteners, curbs, pipes, vents, drains and walls get silicone sealant, and high-stress areas get fabric reinforcement embedded in coating. Once these details cure, they become part of the finished membrane.
The Field Coat and Cure
The field coat is then sprayed or rolled across the entire roof to the dry film thickness the specification calls for. High-solids silicone builds so much film at once that a one-coat system can apply that full thickness in a single pass. A two-coat system splits the same thickness into a base coat and a top coat, often in contrasting colors so the crew can see full coverage. After application, the coating cures from the humidity in the air into a single seamless membrane.
What Silicone Does Well on a Flat Commercial Roof
Standing water is the main reason building owners choose silicone. Snowmelt and rain often sit in low spots on a flat roof for days, and a cured silicone membrane can stay under that water without softening or losing its grip on the roof. That makes it one of the most dependable choices for a flat roof coating where drainage is less than perfect.
Silicone also holds up well under sunlight. Its inorganic chemistry resists ultraviolet light, so the surface stays free of the chalking, hardening and cracking that age brings to many roofing materials.
Most silicone coatings are bright white, and that color changes how hot the roof gets. On dark, absorptive roofs, the difference between roof surface temperature and air temperature can run as high as 90°F, while on roofs with a white coating it is only about 18°F. A cooler roof surface puts less heat into the building below. A cooler surface also eases the daily stress of heating and cooling on the roof itself.
The cured surface resists mold, mildew and staining, which helps the roof stay cleaner between maintenance visits. The installation is also easy on the people inside. With no tear-off, there is no debris coming off the roof, no open deck exposed to weather and no need to close the building. Tenants, workers and customers carry on with their day while the crew works overhead.
Limits and Trade-offs to Weigh
Silicone has a slightly tacky surface, and over time it picks up airborne dirt. As the white surface darkens, the roof slowly loses some of its reflectivity. Regular washing restores most of it, so owners who care about energy performance should plan for cleaning as part of upkeep.
A silicone roof is also slippery when wet, and wet leaves or a light frost make it more so. That matters on roofs with regular foot traffic from HVAC technicians and other trades. Walkway pads along the main paths to rooftop units, or granules broadcast into the wet coating in traffic areas, give workers safe footing.
The cured film is strong and flexible, but it is thinner than a new membrane and has less tear resistance. Sharp debris, dropped tools and heavy traffic can damage it. This is why fabric reinforcement goes into seams, transitions, penetrations and other high-stress areas during installation, and why walkpads earn their place around equipment.
Recoating is the next consideration. Very few materials stick to cured silicone, and that includes new silicone over old once the original coat has aged and gathered dirt. When the time comes to renew the roof, the old surface needs a thorough cleaning and often a compatibility test, and the choices for the new coat are mostly limited to silicone.
Finally, a coating has a clear job and clear limits. It adds no insulation value to the roof, so a building that needs better thermal performance needs insulation work as a separate step. A coating also follows the shape of the roof below it, which means it cannot change slope or fix drainage. Low spots that hold water still hold water after coating, and problems with drains need to be corrected first.
Silicone Roof Coating vs Roof Replacement
Deciding between a roof coating and a replacement comes down to what is under the surface. A coating is usually the better call when the roof is aging but sound, the existing membrane is still adhered, and wet insulation is limited to small areas that can be cut out and replaced. Replacement is the better call when moisture has spread through large areas of insulation, the deck has failed or rusted through, or the roof has gone past the point where it can be restored.
On cost and disruption, the difference is large. Replacement means tearing off the old roof, hauling it away, installing new insulation and membrane, and protecting an open building while the work goes on. A commercial roof coating project skips the tear-off and most of the new material, so it usually costs less than replacement and moves faster, with the building open the whole time.
Skipping the tear-off also keeps old roofing out of the landfill. The United States generated 600 million tons of construction and demolition debris in 2018, more than twice the amount of municipal solid waste, and asphalt roofing is part of that stream.
The building code treats a coating differently from a new roof. Under the 2018 model building code, applying a new roof coating over an existing roof coating or covering is permitted and is not counted as another roof covering layer. The coating does have to be part of the roof assembly's fire classification listing to meet code.
The tax picture can differ too. Under federal tax rules, spending on a building counts as an improvement only when it is a betterment, a restoration or an adaptation to a new use, and other amounts are generally deductible as repairs and maintenance. The answer depends on the facts of each project, so owners review it with their tax advisor.
How Silicone Coatings Handle Michigan Weather
Michigan roofs carry water for much of the year. Metro Detroit averages 45 inches of snow a season and about 34 inches of precipitation over twelve months. When that snow melts in late winter and spring rains follow, water often sits on flat roofs for days at a time. A cured silicone membrane can stay under standing water without breaking down, so it suits these conditions well.
Freeze-thaw cycles are just as hard on a roof. Water works into small cracks, freezes, expands and pries them wider. Silicone stays flexible in the cold and moves with the roof through these swings, so it keeps its seal through the winter. Silicone can also be applied at lower temperatures than water-based coatings, which gives Michigan projects a wider window in spring and fall.
Owners in a heating climate sometimes ask whether a white roof will raise winter heating bills. A reflective roof can add some winter heating use, an effect typically offset by summer cooling savings and smallest on buildings with heavy, long-lasting snow cover. In Southeast Michigan, snow and short winter days already limit how much sun reaches a roof between December and March.
Keeping a Silicone Roof Performing
A coated roof lasts longest with simple, steady care. Plan on an inspection twice a year, typically in spring and fall, plus a check after any major storm. The inspection looks for punctures, worn spots in traffic areas, and any place where the coating has lifted at a seam or penetration.
Washing restores what dirt takes away. Low-sloped reflective roofs need periodic cleaning to keep their reflectance at its best, and a gentle pressure wash every year or two brings a silicone surface back toward its original white.
Drains, scuppers and gutters need to stay clear on every visit. Leaves, debris and loose items left on the roof block water from leaving, and they can cut the coating when they are dragged or stepped on.
Small damage is simple to fix. A cut, a puncture or a lifted seam is cleaned and sealed with compatible silicone sealant, which bonds to the existing silicone when the surface is clean, and a quick repair keeps water from reaching the insulation below.
With that care, the service life is long. We describe our coating roof systems as long lasting, 15 to 20 years, and low maintenance, and a well-kept silicone roof can then be cleaned and recoated to start another cycle.
Coating Commercial Roofs Across Metro Detroit
Shain Roofing & Sheet Metal Inc. installs coating roof systems on flat and low-slope commercial roofs in Livonia, MI and the greater metro Detroit area. When you hire us, the crew on your roof is our family and our own employees. We don't employ subcontractors, and we stay until the job is done.
We are a GACO certified installer. The coating system we install needs no primer on most roofs and has low odor, which helps the building stay open and comfortable during the work, and 15 or 20 year warranty options are available on qualifying systems. For large commercial coating projects, we travel well beyond Livonia.
If your building has a flat roof that is aging but still sound, a silicone coating may give it years of added service without a tear-off. We will walk the roof with you and give you a plain explanation of what it needs, whether that is coating, repair or replacement. To start, Get a Free Estimate with a few details about your building and roof.
