Coating a roof may look like painting — just spray, roll or brush on the finish coat. But that is only the final (albeit most visible) step.
Applying a roof coating system is not difficult, but there is a process to be followed in producing a high-quality, warranty-eligible roof that will deliver years of reliable service. In this article, we’ll outline six simple steps to ensuring a successful project.
1. Train the team.
2. Assess the roof.
3. Repair existing issues.
4. Choose the right coating system.
5. Prepare the surface.
6. Follow the application Instructions.
Step 1: Train the Team
Coating crews can be incredibly productive, with even small crews being able to complete large projects quickly, when each person knows what is expected of them. It starts with training.
Too often, crews are dropped off at a jobsite with no training or experience. They do not understand the specifications that must be met or the processes to follow in doing the work correctly. There is no supervisor onsite to provide guidance. The crew has been set up to fail. People stand around watching, not sure what they should be doing. Quality suffers, with the warranty inspector later leaving a lengthy list of deficiencies to address.
To avoid this, contractors should take advantage of the training provided by the coating manufacturer before beginning their first job. With everyone working from a solid base of knowledge, supervisors can set clear expectations and assign roles. Then, with each crew member understanding their responsibility, the group can work as a seamless team to efficiently deliver a quality project.
Step 2: Assess the Roof
Roof coatings are not “miracles in a bucket.” They will not make an unsound roof sound; unsound roofs must be replaced. They also will not magically fix pervasive leaks, ponding water and other performance issues; these problems must be addressed before the roof is coated, or they will only get worse.
The starting point on any job is, therefore, assessing the roof to determine whether it should be coated and identify necessary repairs. This includes a visual inspection, a moisture assessment and an adhesion test.
Visual inspection: Every roof is different. It is, therefore, essential to walk the roof and experience it up close. Things to look for include:
- Peeling and chalking of existing coatings.
- Poorly attached vents or other projections.
- Open seams and side laps.
- Insufficient slope.
- Damaged membrane.
- Loose membrane on fully adhered roof systems.
- Areas of ponding water (evidenced by the accumulation of dirt or debris).
- Broken or improperly flashed pipes.
- Broken or missing drain components.
- Loose or damaged perimeter edge metal.
- Deteriorated, damaged or loose flashings.
- Damaged or wet insulation or substrates.
Moisture assessment: If the building owner seeks a no dollar limit system warranty, the manufacturer will likely require that a moisture assessment be completed. The easiest and most cost-effective methods are core cuts and moisture surveys.
Core cuts are the roofing equivalent of geologic core samples. Cuts are made to remove samples of all roof layers down to the deck. This deep dive reveals the roof’s age; the components used initially and added since; the installation methods used; the quality of the installation; and the roof’s current condition.
Moisture surveys are a non-intrusive way of finding leaks and determining their severity. A surface meter shoots electrical impulses into the roof to a desired depth, pinpointing where moisture is present and measuring how saturated the roof is. High levels of moisture throughout the roof likely mean the roof should be replaced. Roofs with isolated, lower levels of moisture often can be coated after corrective actions have been taken, including replacing saturated insulation or damaged roof deck.
Adhesion test: A coating’s long-term performance depends on how well it adheres to the substrate. An adhesion test should, therefore, be performed to ensure that the coating is compatible with the substrate and that encapsulated moisture or other underlying issues that could impact adhesion have been properly addressed.
In an adhesion test, a small area of the roof is cleaned and coated. Strips of polyester-reinforced fabric are embedded in the coating, with several inches at the end of each strip left outside the coating to serve as pull tabs. After the coating has fully cured, a fish scale is attached to the pull tabs and used to remove the strip from the roof. The test is a “pass” if the coating remains adhered to the roof membrane and a “fail” if the coating separates completely from the roof surface. The coating manufacturer’s instructions for completing an adhesion test should be followed.
Step 3: Repair Existing Issues
As mentioned above, roof coatings are not cure-alls for an ailing roof. Failure to correct underlying issues before the roof is coated may prevent the coating from properly adhering to the roof, inevitably leading to premature failure.
Specifications from the coating manufacturer should be followed. In general, the existing roof assembly must be structurally sound, watertight and free of shrinkage, buckling, unacceptable ponding conditions, encapsulated moisture, open seams, open or damaged flashings, loose terminations and other serious defects. Coatings should not be applied if the underlying substrate or insulation is saturated with water.
Penetrations, terminations, skylights and other leak-prone areas must be properly sealed. Particular attention should be paid to the transitions between the roof and parapet walls; the two areas respond differently to building movement and temperature swings, making the areas where they meet prime leak locations. Pitch pans should be installed around HVAC units to ensure that the units’ vibration does not create pathways for water to enter the roofing system.
Step 4: Choose the Right Coating System
The variety of roof coating types available — including silicone, acrylic, SEBS, asphalt, aluminized asphalt, urethane and polyurea — provides tremendous flexibility to meet specific project conditions and the building owner’s objectives.
Acrylic and silicone are the most used, with silicone leading the pack by a wide margin. Both will breathe new life into an aging roof. Both can be recoated later to extend the roof’s life even further. Both can enhance a building’s energy efficiency and reduce its environmental footprint. Both can be eligible for a 20-year no dollar limit system warranty. So, which to choose? Factors to consider include:
Ponding water: If the roof occasionally experiences ponding water, silicone coating should be used. No coating will hold up to ponding water on a regular basis, but silicone can withstand it periodically.
Climate: Humidity is an important consideration. Silicone coatings cure by drawing moisture from the atmosphere, while acrylic coatings cure as the moisture in the coating evaporates. Silicone coatings, therefore, cure far more quickly in humid areas and acrylic coatings cure much faster in arid climates.
Existing coating type: Acrylic coatings will not adhere to silicone coatings. A roof that was previously coated with acrylic can be recoated with either acrylic or silicone, but a roof that was previously coated with silicone can only be recoated with silicone.
Cost: Acrylic coatings typically cost less than silicone coatings and may be the right choice when the budget is particularly tight.
Perception: Silicone coatings are generally perceived to be more premium products. If the building owner is planning to sell the building soon, a silicone-coated roof can be an attractive feature.
Step 5: Prepare the Surface
To adhere properly, roof coatings need a clean surface to bond to. Dirt, pollution, oils, bird droppings and other debris must be removed prior to coating, or the coating will adhere not to the substrate, but to the grime, and soon begin to peel off.
Loose coatings and patching material and areas of scaly rust should be removed. Tree debris and other loose contaminants should be picked up. Granulated surfaces should be swept to remove loose particles. This is also a good opportunity to get rid of obsolete rooftop equipment and cables that will make it more difficult to work on the roof and could become sources of leaks.
The roof surface should then be cleaned by applying the manufacturer’s recommended roof wash and power washing. While power washing alone will get the roof clean, the roof wash loosens the dirt, grease and other debris, allowing it to be removed using a lower-pressure power washer, reducing the risk of damaging the membrane.
EPDM roofs often must be cleaned multiple times. The carbon black that gives EPDM its black color releases from the sheeting over time, and that dust must be removed to ensure proper adhesion of the coating. When a hand swiped across the roof surface stays clean, the roof is clean.
Step 6: Follow the Application Instructions
Fluid-applied roofing systems are more than just the finish coat. They are multi-component systems. Each component plays a vital role in the system’s performance and should be used according to the manufacturer’s specifications.
System components: Silicone and acrylic roof coating systems typically include the following:
- Cleaner: The importance of roof wash was outlined above.
- Primer (silicone coating systems): Primer helps ensure strong adhesion of subsequent coats. On asphalt-based roofs, it also prevents bleed-through, preserving the coating’s appearance. On metal roofs, it encapsulates existing rust and inhibits the formation of additional rust.
- Primer (acrylic coating systems): When coating metal roofs, primer is used to encapsulate existing rust and prevent the formation of new rust.
- Sealant: Sealant is used to waterproof and seal fasteners, seams, penetrations and joints and fill and seal pitch pockets and pans.
- Base Coat (acrylic coating systems): Like primer in silicone coating systems, the base coat in an acrylic system provides a well-bonded surface for the application of the finish coats.
- Finish coats: The final layer of a fluid-applied roofing system, finish coats make the roof watertight, protect the roof from the elements and other damage, and can enhance the roof’s energy efficiency.
- Equipment: One of the great advantages of roof coatings is that there is no costly, hard-to-use equipment required to apply them. With an investment of between $2,000 and $3,000, a contractor can have everything needed to start — power washer, power broom, brushes, squeegees and rollers. No special personal protection equipment is needed, just the safety gear, coveralls, eye protection, boots and gloves used on any roofing job.
A spray rig is not essential, but the dramatic boost in production it provides makes it a wise investment. Rigs typically cost between $10,000 and $16,000 and usually pay for themselves on the very first job.
Achieving proper coating thickness: To achieve a high-quality, warranty-eligible roof, base and finish coats must be applied at the wet and dry mil thicknesses specified by the manufacturer. Two techniques can make this easy to achieve.
The first is simple teamwork. Crew members work in pairs, with one applying the coating and the other following behind with a wet mil gauge, measuring and letting the applicator know when the coating is uneven or too thin.
The second works well on wide-open roofs with few obstructions from HVAC equipment, pipes, cables and communications equipment. The crew determines how many square feet of roof surface one pail of coating will cover at the desired thickness and then uses chalk to mark a grid of squares that size. A pail can then simply be emptied into the center of each square and the coating spread evenly with a roller or squeegee to its edges.
Applying a fluid-applied roofing system is easy, but there are nuances to understand, specifications to adhere to and processes to follow. Following the six steps outlined here can help ensure a coated roof will deliver years of reliable, client-pleasing performance.
About the Authors: Vincent Martinez is fluid-applied segment manager and Mark Malin is national product manager for low-slope roofing manufacturer Mule-Hide Products Co. For more information, visit mulehide.com.
Originally Published by Roofing Magazine in the November/December 2024 Issue