Commercial Roof Coating Cost Calculator

With the defaults, 10,000 sq ft of silicone coating on a fair roof comes to $26,900, or $2.69 per sq ft. That is $18,500 for the coating, $1,500 to pressure wash the roof first, $3,000 to reinforce seams and flashings, $2,000 of repairs, $700 to detail 20 penetrations and $1,200 of mobilization.

The coating type and the warranty move the price the most. With the same roof, acrylic comes to $19,400 and polyurethane to $31,400. Extending the silicone system from a 10-year to a 15-year warranty takes the job to $31,525, and a 20-year system to $36,150, or $3.62 per sq ft. Roof condition matters too: a good roof with no repair line comes to $24,900, and a poor roof with the higher repair rate comes to $30,900.

Fixed charges make small roofs cost more per square foot. The same default job costs $2.88 per sq ft at 5,000 sq ft, $2.58 at 25,000 sq ft and $2.52 at 100,000 sq ft. A very small, clean roof (1,000 sq ft of silicone on a good roof with no washing, seams or penetrations) adds up to $3,050, which the calculator raises to the $4,000 minimum job charge. The extras are easy to forget: primer adds $2,500 to the default, seam reinforcement is $3,000, and 100 penetrations instead of 20 take the job to $29,700.

The calculator compares the coating job with a full re-roof priced at $8 per sq ft, which is a placeholder rather than a quote, so replace it with a bid for your roof. At that figure the default 10,000 sq ft roof would cost $80,000 to replace, and the $26,900 coating costs about a third of that, a difference of $53,100. Even a 20-year polyurethane system with primer on a poor roof comes to $49,400, still below that $80,000. The gap narrows as repairs, penetrations and the fixed mobilization charge add up, especially on a small roof, so run the comparison with a real re-roof bid.

The price is only half of the decision, because a coating does not replace a failed roof. Benchmark, a roof and pavement consulting firm, puts it this way: some existing roof systems can benefit from a roof coating, but in other cases coatings are not a wise investment. The comparison number is useful for budgeting, and the roof inspection decides whether coating is the right tool.

A coating can only seal and protect what is underneath it. It cannot hold up a roof whose insulation has soaked through. Benchmark recommends a moisture survey to identify areas of wet insulation and says the results should be used to decide whether coating is viable. It also says failed areas, including leak areas and wet substrate materials, must be removed and replaced with dry, sound materials, and that a coating applied over moisture-laden insulation will most likely blister and fail.

In practice, a moisture survey comes before any coating proposal. Surveys often use an infrared camera or a moisture meter, followed by a few core cuts to confirm the readings. If it finds wet insulation, that area is typically cut out and replaced first, and the cost of that work belongs in the repair line. The calculator prices repairs per square foot of roof from the condition you choose: none on a good roof, $0.20 on a fair roof and $0.60 on a poor roof. Replacing wet insulation can cost more than that, so use the repair price to enter what a contractor quotes after the survey.

Ponding water is the other thing to settle before you choose a product. Benchmark says ponded water, especially when it is heated by UV exposure, can lead to the breakdown of the coating, and lists acrylic as a coating that may not perform well in ponding water situations. It lists silicone and polyurethane as good or resistant in ponding water situations.

Acrylic is the lowest-cost option and is water-based. Benchmark gives it an anticipated service life of five to ten years, depending on chemistry, application and maintenance. Silicone costs more and handles ponding water; Benchmark gives it ten to fifteen years. Polyurethane costs the most in the calculator; Benchmark gives it seven to ten years and says it should be used with a fabric.

A longer warranty typically comes with a thicker coating system, which is why the calculator multiplies the coating line by 1.25 for 15 years and 1.5 for 20 years. Treat those multipliers as an estimating rule, because the exact system, thickness and price come from the manufacturer and the applicator. A warranty term also does not always equal the life of the roof. Benchmark notes that, in its experience, performance life and warranty term are not necessarily equal, and that many extended warranties cover the cost of new material only and exclude the costs of roof preparation and coating application. Read the exclusions and the maintenance requirements before paying for a longer term.

A white or light coating reflects sunlight, which is the reason many owners coat a flat roof. The EPA says a high solar reflectance, or albedo, is the most important characteristic of a cool roof, and it lists liquid-applied roof coatings with light or cool colors among the low-slope cool roof products. For an air-conditioned building, a cooler roof usually means less cooling load, though the savings depend on the climate, the insulation and the building. The EPA reports peak cooling demand reductions of 11 to 27 percent for air-conditioned residential buildings, which is not a figure for your building.

If you want a coating that qualifies for an ENERGY STAR label, the program requirements for low-slope roof products, which include roof coatings, call for an initial solar reflectance of at least 0.65 and a reflectance of at least 0.50 three years after installation. Reflectance falls as dirt collects, and the program requirements give rinsing or power washing each spring or recoating every five years as examples of maintenance that protects it. Washing before coating is also common practice so the coating goes onto a clean surface, and the calculator prices it as its own line; follow the manufacturer's preparation instructions.

Primer, seam reinforcement and penetration detailing are the other preparation items. Primer is optional and depends on the roof surface and the manufacturer's instructions, seam and flashing reinforcement adds material at seams and flashings, which are common leak points on a flat roof, and each vent, drain, curb or pipe is detailed by hand. Switch them on or off to match the scope in the bid you are comparing.