Low-slope roof coating restoration system field guide

Roof restoration coating, and where it fits

A roof restoration coating is a fluid-applied membrane that goes over an existing low-slope roof to renew it instead of replacing it. It is rolled, sprayed, or squeegeed on as a liquid, it cures into a continuous, monolithic film, and it bonds to the roof already there: built-up, modified bitumen, metal, or single-ply. Done on the right roof, it seals the surface, bridges the small splits and weathered seams, adds a reflective top, and resets the warranty clock without a tear-off.

The pitch is real and so is the limit. A restoration buys years on a roof that still has good bones, at a fraction of the cost and disruption of stripping to the deck. It also fails fast and ugly on a roof that does not qualify, because a coating is a surface treatment, not a structural repair. It cannot dry out wet insulation, it cannot re-bond a delaminated membrane, and it cannot make a roof that is already leaking everywhere watertight by painting over it.

So the whole job is two decisions made before a pail opens. Is this roof a candidate, and which system suits it. Get those right and the application is execution. Get them wrong and you have spent good coating on a roof that was headed for the dumpster anyway.

Is a coating restoration cheaper than a tear-off?

A coating restoration usually costs well under a tear-off and reroof when the roof qualifies, because you keep the existing membrane and insulation and skip the demolition, the disposal, and the deck exposure. There is no dumpster, no torn-open building during a rain, and far less labor. On a sound roof, that is the case for restoration in one sentence.

The other half of the value is the recover without a recover. A coating is not a new roof layer the way a second membrane is, so it usually does not count against the code limit on the number of roof systems, commonly two, that forces a tear-off once a roof has already been covered once. Confirm that against the adopted code and the manufacturer, but it is a real advantage on a roof that has been recovered before and cannot take another layer.

What restoration does not do is fix what is wrong underneath. A tear-off lets you correct wet insulation, bad drainage, and failed details and start the warranty on a clean deck. A coating renews the surface and leaves the assembly as it is. The decision rule is honest: if the roof is sound and dry, restore it and save the money. If the assembly has failed, a coating just delays the tear-off and adds a layer the demo crew has to deal with later.

Is my roof a candidate for a restoration coating?

A roof is a candidate for restoration when the substrate is sound, dry, and not failing, and it is not a candidate when any of those is missing. The coating bonds to and protects what is there. It does not rebuild it. So the qualifying inspection is looking for a roof with life left and water out, not a roof at the end of its run.

Sound means the membrane is still attached and intact in the field, the insulation has compression and R-value, and the deck is solid. Dry means no trapped moisture in the insulation or the substrate, which you confirm with a moisture survey and core cuts, not a look. Not failing means the leaks are isolated and repairable details, not widespread membrane breakdown. The full qualifying walk, the drains, the flashings, the wet-insulation map, and the repair-versus-replace call, is the work covered in the companion guide on the roof inspection and maintenance program, and a restoration starts from exactly that assessment.

The blunt version: a coating does not fix a failed roof. If the moisture survey lights up half the roof, if the membrane is shrunk off the corners, if the deck is soft underfoot, you are looking at a tear-off and the coating money is wasted. Qualify the roof first. The chemistry and the mils only matter on a roof that earns the coating.

Trapped moisture is the one condition that kills a restoration before it starts, so a moisture survey is the gate, not an option, on any roof old enough to have leaked. Wet insulation does not dry out under a sealed coating. It stays wet, keeps destroying the assembly, and pushes vapor up under the new film until it blisters and delaminates the coating you just paid for. You coat over water and you own the failure.

Run the survey before you commit. Infrared, nuclear, or capacitance methods map where the water already is, and core cuts verify the map, the same survey work the inspection guide details. The industry rule of thumb that has held up in practice: if the wet substrate is a small share of the roof, commonly cited around a quarter of the area or less, those sections get cut out, dried, and replaced with sound dry material, and the rest can be coated. Past that, the honest call is a tear-off, because you are replacing so much of the roof that restoring the remainder makes no sense.

Active leaks get found and fixed at the source, and the wet area dries fully, before any coating goes on. The substrate has to be dry through, not dry on top. This is the spec-versus-reality gap that bites applicators: the data sheet assumes a dry substrate, and on an aged roof you only know it is dry by surveying and cutting, never by the calendar or the feel of the surface.

The coating chemistries and where each one fits

Four chemistries cover almost all restoration work, and they sort by drainage, cost, and traffic before anything else. Silicone is the ponding and weathering leader, a high-solids moisture-cure coating that shrugs off standing water and UV and dominates flat commercial roofs that hold water. Acrylic is the value and reflectivity play, a water-based coating that is cheaper and bright white but breaks down under standing water, so it belongs on roofs that drain. Polyurethane brings toughness, with an aromatic base coat for impact and abrasion under an aliphatic top coat for UV stability, which is why it shows up where there is foot traffic or where a harder film is wanted.

Two more fill out the list. SEBS and other rubber-modified coatings are solvent-based and stay flexible in cold, useful on metal and in cold climates. Asphaltic and bituminous coatings, aluminized or fibered, are the old-line, low-cost option on BUR and mod-bit, more a maintenance coat than a warranted restoration system. Each chemistry has a substrate and a service condition it suits, and the manufacturer's published system tells you which substrates it is approved over.

Pick the chemistry to the roof, then size the mils to the chemistry and the warranty. The order matters. The drainage and the substrate choose the chemistry, the chemistry sets the dry film thickness the warranty demands, and the dry mils set the gallons, which is the math worked in the companion guide on coating mil thickness and coverage yield.

Can you coat a roof that ponds water?

You can coat a roof that ponds, but only with silicone, and only with eyes open about what the coating does and does not solve. Silicone is the one common chemistry that holds up to standing water, because it is not water-based and does not re-emulsify or soften when water sits on it for days. Its polysiloxane film is hydrophobic and UV-stable, which is why it is the default on low-slope commercial roofs with dead-flat areas and drainage that never quite worked. Acrylic on a ponding roof is a built-in failure, because the water softens and breaks down the film.

Tolerating ponding is not the same as ignoring it. Silicone in confirmed ponding areas is usually specified at a higher dry film thickness, commonly around 40 mils, because standing water is a harsher service condition, and the manufacturer's warranty still has the final say on whether ponding is covered at all. Read the drainage language before you promise a ponding roof anything.

Two field facts about silicone earn their keep. It gets slick when wet, so it is a slip hazard for anyone walking it after rain or dew, and a walk-pad granule broadcast at the details is worth specifying where traffic happens. And silicone only re-coats with silicone. Nothing else bonds reliably to a cured silicone surface, so you are committing the roof to a silicone future the day you choose it. A coating restores the surface, not the slope, so if the roof ponds because it has no drainage, adding slope is the real long-term fix, covered in the tapered-insulation work referenced in the mil and yield guide.

The acrylic cool-roof restoration

Acrylic is the value restoration on a roof that drains. It is a water-based elastomeric coating, it is the cheapest of the warranted systems per gallon, and it cures to a bright white reflective surface that makes it the common cool-roof choice. On a sloped metal roof or a single-ply that sheds water, acrylic does the job at a price silicone cannot match.

The hard limit is ponding. As a water-based film, acrylic softens and breaks down where water stands, so it belongs only on roofs that drain, commonly within about 48 hours after rain, and it is the wrong call on a dead-flat roof with low spots. The other limit is cure. Acrylic needs warm, dry weather to coalesce into a film, commonly applied above 50 degrees F with no rain, dew, or freeze in the cure window, because the water in it has to evaporate for the film to form. Coat acrylic late in a cool day and the dew that lands before it cures washes it off the roof.

Acrylic is also frequently applied as a two-coat system, often a base and a contrasting top so the applicator can see the coverage, and it reaches its warranted dry mils across two passes rather than one heavy coat. The mils, the solids, and the gallons math is the same engine as any other chemistry, run in the companion mil and yield guide.

How do you prep a roof before coating?

Surface prep is where most coating failures are born, because a coating bonds to a clean surface, not to the grime on top of it. The roof has to be cleaned of everything that sits between the coating and the substrate: dirt, oils, bird droppings, biological growth, and chalk. If the roof is dusty, the coating sticks to the dust instead of the roof, and it blisters and peels months later. Clean is not cosmetic. It is the bond.

The standard sequence is the manufacturer's roof cleaner worked over the surface, then a power wash, commonly around 2000 psi, with a stronger cleaner such as a TSP-type product for stubborn grease and growth, then a clean-water rinse and a full dry before anything else goes on. Power washing alone gets the roof visually clean. The cleaner is what gets it bonded-clean, and the difference is the part that lifts off in a year.

Chalk deserves its own mention, because it fools people. Chalk is not settled dirt, it is the powdery residue of the old coating or membrane degrading, and it has to be removed by washing or the new coating bonds to a layer that is already letting go. The way to confirm the surface is actually clean is a tape check: press tape down and pull it. If it comes off tight and clean, the surface is ready. If it lifts loose powder, the roof needs more washing. And the roof has to be dry before the primer or coating, because a coating over residual surface moisture has the same problem as a coating over a dirty one.

The adhesion test patch

Before you coat the whole roof, you find out whether the coating will stick, and you do it with a test patch, not a hope. The adhesion test is cheap insurance against the most expensive failure there is: a coating that peels off the entire roof because it never bonded. Run it on every questionable substrate and in several spots, because a roof reads different in different areas, some shaded, some chalked, some oilier than the rest.

The common test is a small coated patch, often a 6 inch square brushed onto the cleaned surface, or the version with a fabric pull tab: lay down about 15 wet mils of coating, embed a 1 inch by 6 inch strip of polyester fabric leaving an inch hanging free, then saturate it with another 15 wet mils. Let it cure the manufacturer's full time, commonly several days, then pull the tab at 90 degrees to the roof. The read is simple. If coating tears and stays stuck to the substrate, the bond is good. If the tab peels off and leaves clean substrate behind, the adhesion failed and you prime, change the prep, or change the system until it holds.

This is the step that separates the applicators who get callbacks from the ones who do not. The test takes a few days of lead time and a few dollars of material, and it tells you before the pull whether the whole roof is going to bond. Skip it to save the lead time and you are betting the entire job on a guess.

Repairs and seam reinforcement first

The coating goes on last, after the roof is repaired, because a coating bridges small movement, not open failures. Splits get cut, cleaned, and patched. Open or fishmouthed seams get repaired. Loose flashings, cracked pipe boots, failed pitch pockets, and backed-out fasteners all get fixed before the field coat, because a film stretched over an unrepaired split will tear there the first time the roof moves. Fix the roof, then coat it.

Reinforcement is how the coating survives the spots that move the most. Polyester reinforcing fabric is embedded into the wet coating at the trouble areas, the seams, the laps, the flashings, the fastener rows, the penetrations, and the curb bases, to add tensile strength, tear resistance, and crack-bridging where a plain film alone would split. The fabric runs in a three-course detail: a base coat of coating, the fabric broomed or rolled into it while wet so the coating wets fully through the weave, then a top coat that saturates and locks it in, commonly built to a wet film around 24 to 30 mils across the detail. Fabric sizes in the 4 to 12 inch range cover most seam and flashing details.

Two things separate a real reinforced detail from a defect. The fabric has to be fully encapsulated, coating top and bottom, with no dry threads showing and no bridging where it spans a gap without contact. And the detail has to carry its share of the total dry mils, so it drinks more coating than the plain field, which the takeoff has to account for or the reinforced areas run short. A detail-reinforced system fabrics only the trouble spots and coats the field plain. A fully reinforced system carries fabric across the whole roof. The spec says which you are building.

Do you need a primer? Plus rust and the metal roof

Whether you need a primer depends on the substrate, and the way to settle it is the adhesion test, not a guess, but several substrates almost always call for one. The primer does one of three jobs: it improves adhesion where the coating will not bond directly, it inhibits rust on metal, or it blocks bleed where the substrate would stain through a light coating. RCMA's guidance on the use of primers before roof coating, sometimes cited as a coatings technical note, frames when each applies, and the manufacturer's system specifies the exact primer for each substrate.

On metal, a rust-inhibiting primer is part of the system wherever rust is present, because it penetrates and binds the corrosion of the ferrous metal so the rust stops spreading under the film and so the coating bonds. On asphalt, built-up, and modified-bitumen roofs, a bleed-blocking primer keeps the lighter fractions of the bitumen from striking up through a white coating and staining it brown, which is a cosmetic failure on a cool roof and a sign the asphalt is bleeding into the film. On single-ply, the right primer for that specific membrane, EPDM, TPO, or PVC, is what makes a coating bond to a sheet that was made to shed everything.

Match the primer to the substrate every time, from the manufacturer's system for that membrane, and confirm the coating is even approved over that single-ply, because not every coating bonds to every sheet. The primer is the difference between a coating that grips and one that the next wind storm peels back at a corner.

A metal roof restoration lives or dies on three things the rest of the roof does not have: rust, fasteners, and the panel seams. The coating over the field is the easy part. The leaks are at the laps and the fastener heads, and the failure under the coating is rust that was never stopped.

Deal with the rust first. Active rust keeps spreading under a film and lifts it, so the loose scale gets wire-brushed or ground off, and a rust-inhibiting primer goes over the cleaned metal to bind what remains and stop the corrosion. Then the fasteners: backed-out and stripped screws get reset, oversized, or replaced with larger fasteners, and gasketed fasteners that have failed get attention, because a fastener that has worked loose is an open hole. Then the seams: the panel laps and the ridge get detailed with reinforcing fabric in coating before the field coat, because that is where the panels move and where the water already gets in.

Only after the rust is stopped, the fasteners are tight, and the seams are reinforced does the field coat go on, usually a silicone or an SEBS system that stays flexible over the metal's thermal movement. A coating over live rust is a coating with a built-in lift-off date.

Mil thickness, coverage, and applying the coating

The coating only performs and only carries its warranty at the manufacturer's dry film thickness, measured in mils, thousandths of an inch. Go thin to stretch the pail and the membrane chalks off early, splits at the seams, and fails the closeout inspection, which voids the warranty for the whole roof. The dry mils are not where you find savings on a restoration. They are what the whole job is built to hit.

The full math, wet mils versus dry mils, percent solids by volume, the 1604 coverage constant, the loss factor, the target dry film thickness by chemistry, and the gallons-per-square takeoff, is worked end to end in the companion guide on roof coating mil thickness and coverage yield. The short version for the restoration system: pick the chemistry, pull the warranted dry mils and the volume solids from the data sheet, convert to the wet mils you apply, cut the theoretical coverage by a realistic loss factor for the surface texture, and order gallons against that practical number. A contrasting color between base and top coat lets the applicator see where the second coat ran thin before it cures in invisible.

Restoration coatings go on by airless spray, by roller, or by squeegee-and-back-roll, and the method trades speed against control. Spray covers a big roof fast but loses 15 to 30 percent to overspray and wind and demands masking of everything you do not want coated. Roller and squeegee work loses less, often 5 to 10 percent, and gives more control at the details, which is why many crews spray the field and hand-work the edges and penetrations. On a windy day the spray comes down entirely, because overspray drifts onto cars and neighbors and your loss factor goes through the roof.

The back-roll matters more than it looks. On a textured or granulated surface, rolling behind the spray pushes the coating down into the texture so it builds film instead of bridging over the high spots, which is where a sprayed-only coat goes thin without anyone seeing it. Read wet mils on a notched gauge as you go, on a grid every few hundred square feet and extra at the details, so the thin spots get caught wet, not after they cure.

Respect the recoat window between coats. Each coat has to cure enough to take the next without lifting or trapping uncured material underneath, and that window is set by the product, the temperature, and the humidity, so it comes off the data sheet, not the clock in your head. Apply the base, hit the wet mils, let it reach its window, then top-coat the rest of the target. Rush the second coat onto a base that has not set and you trap solvent or water and get a soft, blistering film.

What weather do you need to apply a roof coating?

The application window is part of the spec, not a suggestion, because weather decides whether the coating cures into a membrane or never gets the chance. The common envelope keeps the air and surface temperature inside the product's range, often roughly 50 to 85 degrees F with the surface below about 90, the relative humidity at or under about 85 percent, and the substrate at least 5 degrees F above the dew point during application and cure. Confirm the exact numbers on the data sheet, because they shift by chemistry.

The dew point rule is the one applicators skip and regret. The 5 degree margin above the dew point is a cross-chemistry standard referenced by RCMA, and the reason is simple: a substrate at or below the dew point has invisible condensation on it, so the coating goes down onto a film of water instead of onto the roof, and it never bonds. Check the surface temperature and the dew point with a meter, not your hand, first thing in the morning and late in the day when the roof is cool.

Then there is the rain window, and washing off an uncured coating is a full redo. The do-not-apply list is short and firm: no rain, dew, fog, or freeze expected during the cure, commonly a 24 to 48 hour rain-free window for many coatings, longer for some, and silicone often needs up to 72 hours to cure fully because it cures by reacting with humidity in the air. Acrylic is the least forgiving, because its water has to evaporate, so a cool damp evening that lands dew before it cures takes the coating right off the roof. Watch the forecast, not just the sky at the start of the day.

The warranty, maintenance, and the renewable re-coat

The reason a building owner pays for a warranted system instead of a maintenance coat is the manufacturer warranty, and on a restoration it is tied directly to the dry mils, the prep, and the approved applicator. The warranty term rides on the dry film thickness, with more mils buying more years on the manufacturer's published ladder, and it is released by a field inspection at closeout that checks the prep, the details, the reinforcement, and the mils across the roof. A roof that reads light fails the inspection no matter how good it looks.

The terms that govern are the manufacturer's, full stop. Many restoration systems carry a manufacturer's warranty in the 10 to 20 year range depending on the system and the mils, and the longer no-dollar-limit style coverage carries maintenance and inspection conditions the same way a new membrane warranty does. Read the document. It states the required mils, the approved prep and primer, who may apply it, and what maintenance keeps it in force.

The renewable part is what makes restoration attractive over the long run. At the end of the warranty term, commonly 10 to 15 years out, a sound coated roof can usually be cleaned and re-coated to renew the system and the warranty again, without a tear-off, as long as the chemistry is compatible with itself, which for silicone means silicone. That renewability is the difference between a roof you restore on a cycle and a roof you replace.

A coated roof is still a roof, and it earns its full life only on a maintenance program, the same spring-and-fall plus post-storm cadence covered in the companion guide on the roof inspection and maintenance program. The coating renews the surface. It does not relieve the owner of clearing the drains, checking the details, and catching the dropped-tool puncture before it becomes a leak. A coated roof with blocked drains ages just as fast as any other.

The maintenance walk on a coated roof watches a few coating-specific things on top of the usual inspection: thin or worn spots where traffic or weather has taken the film down, areas where the coating has chalked or lost reflectance, details where the reinforcement is showing through, and any blistering that signals moisture working up from below. Caught early, a worn area is a clean-and-recoat patch. Ignored, it is the start of the failure.

The prep before a re-coat decides whether it bonds. The existing membrane has to be washed clean of dirt, chalk, and biological growth, the seams and flashings checked and repaired, and an adhesion test pulled where the old coat is weathered, because the new coat is only as good as what it sticks to. Budget the re-coat as a scheduled capital item off the maintenance program's condition data, and do it while the roof is still sound, not the year it starts leaking, when the prep gets harder and the savings are gone.

The cool roof: reflectivity, energy, and the rebate

Most restoration coatings are reflective, white or light, and a reflective roof bounces solar heat back instead of soaking it into the building, which cuts cooling load and surface temperature. That energy benefit is a real part of the restoration value, and it comes with its own set of numbers separate from the waterproofing: solar reflectance, thermal emittance, and the combined solar reflectance index, or SRI, that rating programs use.

Where it pays off in dollars is the energy code and the rebate programs. Cool-roof requirements appear in energy codes in hot climates, with California's Title 24 the well-known example, and utility and program rebates often turn on the coating meeting a reflectance or SRI threshold and being listed by a rating body. Those reflectance values are a separate check from the waterproofing spec and a separate qualification from the warranty, so confirm the cool-roof requirement against the adopted energy code, the rating program, and the specific product.

One field note. Reflectivity drops as the roof picks up dirt and weathers, so the aged reflectance, not the day-one number, is what the energy benefit runs on over time, and it is part of why washing the roof on the maintenance cycle matters for more than just the bond. A dirty white roof is a less reflective roof.

Quality control on a coating job

Quality control on a restoration is the evidence that the coating will last, and it happens during the work, not at the end, because the dry mils and the bond cure in invisible the day after the crew leaves. The applicator who runs QC as they go finds the thin area and the dry-threaded detail while they are still fixable. The one who waits for the inspection finds them when the manufacturer's rep does.

Five checks carry the job. The wet-mil reading on a notched gauge across a grid, every few hundred square feet and extra at the details, so the dry mils land where the warranty wants them. The adhesion test before the field coat, confirmed by the pull. The reinforcement check, that the fabric is fully encapsulated with no dry threads or bridging. The dry-film confirmation after cure, a destructive plug or core on most roofs or a gauge on metal, which is the reading the warranty inspector trusts. And the holiday check, looking for the pinholes, skips, and missed spots a single pass leaves, which is exactly why the spec calls for two coats in contrasting colors so any base color showing through marks a thin spot.

Tie every check to a place and a number as you go. A wet-mil log with no locations is a log nobody can act on. The grid of readings, the gallons-per-square actually applied, and the photos are what turn the closeout inspection into a signature instead of an argument.

Restoring a large flat roof over a data center

On a big-box, warehouse, or data center roof, the math that favors restoration gets sharper and the stakes underneath get higher. The acres of low-slope membrane over a distribution center or a data hall are exactly the roofs a coating restoration suits, sound aging single-ply or BUR over a building that cannot easily be taken offline for a tear-off, and the cool-roof energy savings across that much area are real money on the cooling bill.

What changes over a critical space is the tolerance for a miss. A leak over a data center white space is not a stained ceiling tile, it is downtime or damaged equipment, so the restoration over that area is held to a tighter standard: more reinforcement at the details, a chemistry chosen for the drainage with no compromise, and closer QC on the mils directly over the critical zone. The application also has to respect the operation below, no overspray drift into intakes, no coating fumes drawn into the building, and tight control of rooftop traffic during the work.

The phasing matters too. A roof this size gets restored in sections coordinated with the building's operation and the weather window, and each section gets its own moisture survey, prep, and QC record, because over a building measured in uptime the roof file is part of the risk record, not an afterthought.

How restoration coatings fail

Restoration coatings fail in a short list of ways, and almost every one traces to a decision made before the pail opened. Name the mechanism and you know which decision to get right.

The big one is coating over a wet or failed roof. The trapped moisture vapors up under the sealed film and blisters and delaminates it, and the failed assembly keeps failing underneath, so the coating just delays the tear-off and adds a layer. Next is no prep or bad prep: the coating bonds to dirt, chalk, or oil instead of the substrate, and it peels, usually starting at a corner or an edge within a year. Then the wrong chemistry for the drainage, acrylic on a roof that ponds, which softens and breaks down where the water sits.

The rest round out the list. No seam reinforcement, so the film tears at the splits and seams the first time the roof moves. Under the mils, where the membrane is too thin to bridge movement or survive UV for its rated life and fails the warranty inspection. And application into bad weather, where the coating goes onto condensation below the dew point and never bonds, or washes off in a rain that came before it cured. Every one of these is preventable, and every one is cheaper to prevent than to recoat.

What to document

The record on a restoration is what proves the system was built right and earns the warranty, and it is the difference between a paid claim and a denied one years out, because the mils and the bond cured invisible the day the crew left. Document by area as you work, so a reading ties to a place on the roof.

Capture the section of roof, the substrate and its condition, the prep done and the cleaner used, the adhesion test result, the primer applied, the coating chemistry and the target dry mils, the wet mils read on the grid, the reinforcement detail, the gallons used, and the weather, temperature, dew point, and humidity at application. Carry the actual gallons-used back against the takeoff so the next estimate calibrates to your real loss factor. The estimate that records its own assumptions and the field readings against them is exactly the funnel a tool like FieldOS is built to hold, and it is the file the warranty inspection runs against.

Common mistakes

• Coating over a wet or failed roof, so trapped moisture blisters the film and the failed assembly keeps failing underneath.
• Skipping the moisture survey and the core cuts, then sealing water into the roof under a fresh warranty.
• Coating a dirty, chalky, or oily surface with no proper wash, so the coating bonds to the grime and peels.
• Not running an adhesion test patch, then discovering the whole roof did not bond after it is all coated.
• Repairing nothing and reinforcing no seams, so the film tears at the splits the first time the roof moves.
• Putting acrylic on a roof that ponds, where a water-based coating softens and breaks down under standing water.
• Going thin on the dry mils to stretch the pail, which voids the warranty for the whole roof.
• Skipping the rust-inhibiting or bleed-blocking primer on metal or asphalt, then watching rust or stain strike through.
• Applying below the dew point or into a rain window, so the coating goes onto condensation or washes off before it cures.

Field checklist

Standards and references

The document that governs a restoration is the coating manufacturer's published system and warranty, full stop. It sets the approved substrates, the prep and primer for each, the target dry film thickness tied to the warranty term, the reinforcement details, the application conditions, and who may apply it, and the closeout inspection runs against it. Everything else is the framework around that controlling document, so confirm the specifics against the actual product.

The ASTM material specifications define what each coating type has to be: ASTM D6694 for liquid-applied silicone coatings used over spray polyurethane foam, ASTM D6083 for liquid-applied acrylic roof coatings, with the urethane and other chemistries falling in the same ASTM D08 roofing family, some revised or withdrawn across the cycles, so confirm the current designation. The wet-film and dry-film measurement methods and the coverage math are carried in the companion mil and yield guide. Cite a designation only after confirming the edition, because they change.

Industry guidance comes from the Roof Coatings Manufacturers Association, RCMA, whose coatings technical notes cover the use of primers and the application conditions including the dew-point margin, and from the NRCA for low-slope roofing practice generally. The cool-roof and energy side intersects through the adopted energy code, California's Title 24 being the common example, and the reflectance rating programs, which are a separate check from the waterproofing spec. Through all of it the project specifications and the adopted code edition with local amendments control, and the manufacturer's warranty overrides any rule of thumb on the chemistry, the prep, and the mils.

Units, terms, and references

A restoration job reads across a data sheet, a spec, and a warranty, and the same idea shows up under different names, so a short glossary keeps the crew and the inspector talking about the same thing.

Thickness is in mils, one mil being one thousandth of an inch, about 25.4 microns. Coverage is in square feet per gallon or gallons per square, a square being 100 square feet of roof. Reflectivity shows up as solar reflectance, thermal emittance, and the combined SRI. Ponding is water standing more than about 48 hours after rain. The terms below are the ones specific to a coating restoration.

Restoration coating

A fluid-applied membrane coated over an existing sound roof to renew it and extend its life without a tear-off

Recover vs restoration

A recover lays a new membrane over the old as a roof layer; a restoration coats the existing roof and usually does not count as a new layer

Moisture survey

An infrared, nuclear, or capacitance scan, verified by core cuts, that maps wet insulation before a roof is coated

Adhesion test

A small coated patch or fabric pull tab cured and pulled to confirm the coating bonds to the substrate before the field coat

Reinforcement fabric

Polyester fabric embedded in the coating at seams and details for tensile strength and crack-bridging

Bleed-blocking primer

A primer that keeps asphalt or bitumen from staining up through a light-colored coating

SRI / cool roof

Solar reflectance index, the combined reflectance and emittance rating used by energy codes and rebate programs for reflective roofs

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