Protecting Against Chemical Overspray

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Protecting Against Chemical Overspray

By Diane M. Calabrese



Soap, acids, abrasives, or the use of any sort of chemical tends to heighten awareness of overspray. It should not. “Overspray has to be taken into consideration on all jobs,” says Michael Hinderliter, president, Steamaway, Inc. in Fort Worth, TX. “Even when just cleaning with water.”

The first step on any job, explains Hinderliter, is to determine where overspray will go. “Once this is determined, then a decision regarding how best to protect those surfaces can be made.”

Start by assessing the property in the context of the weather conditions. “Consider the direction of the wind,” says Hinderliter. If there is likely to be spray carried by wind, take action. “Protect surfaces exposed to overspray with a sheet of plastic, tarp, canvas, etc.,” says Hinderliter. “Thin, clear plastic sheeting is relatively inexpensive but may not always be the best option. For example, covering plants in the hot summer sun with clear plastic will trap heat and moisture, causing extreme temperatures that will kill plants.”

A better option for some plants might be a canvas tarp or colored plastic tarp, says Hinderliter. In certain circumstances, though, it’s better to outwait weather. “We cleaned some silos years ago with some strong degreasers,” says Hinderliter. “We had to be concerned with overspray. We did not wash during high wind and during employee shift changes.”

Knowing the chemical being used—its proper use and the risks inherent in its use—is essential to achieving appropriate protection. “I would consider any overspray that is corrosive or coating to pose the highest risk,” says Hinderliter. “Corrosive solution, such as a strong acid or caustic, can easily have a chemical reaction causing irreversible damage. Coating, such as a stain or sealer, can be extremely difficult to remove.”

Doing everything that can be done, including working with optimal weather, to eliminate overspray is the goal of all professional contractors. So, too, is using the least harsh chemical that will do the job.

Care All-Around

“Unintended consequences of water” is a synonym for overspray used by Mike Hilborn, owner, Roof-to-Deck Restoration and RTD Power Washing in St. Paul, MN. The unintended consequences “can make power washing dangerous.”

People, pets, and plants—living things, all—must be protected from such consequences. So, too, must the inanimate objects in the environs, which range from cars to concrete statuary. Siding poses an additional concern.

“Anything that lands on and affects siding is a serious problem,” says Hilborn. “If bad enough, siding will need to be replaced or houses will need to be repainted.” Similarly, paving stone and concrete, if negatively affected, would have to be replaced. A contractor wants to avoid such problems.

Every project presents its own challenges. Evaluation of the setting is where it begins. “Always hire a professional,” says Hilborn. The professional will take the appropriate precautions.

“If we are protecting against chemicals, we use the pre-wet and post-wet method,” says Hilborn. “That is soak the siding and grass and plants with water, immediately apply the chemicals, and then immediately rinse the siding, grass, and plants with water again.” The pre-wet method puts the physiology of plants on the side of protecting them. Roots will not absorb wash water if the plants have had sufficient access to water. 

“If you water grass and plants well, they are not thirsty when the chemical is applied,” says Hilborn. “It will simply be on the surface and not consumed. Rinsing the chemicals off the grass and plants before the chemicals have a chance to dry, prevents the plants from being damaged.”

Getting plant physiology on the side of the contractor is more difficult in some circumstances, such as hot weather, explains Hilborn. “Hot days are when the most damage can occur,” he says. Hilborn also says avoid covering plants with clear plastic because the “heat builds so quickly” it becomes lethal to them. “Blue, brown, or green tarp is safer.”

Some surfaces and substrates are more tolerant of chemicals than others. “If you are stripping a deck with rock or gravel or concrete below it, it is not necessary to protect the ground from the stripper,” says Hilborn. The same surfaces will have to be protected from stain and sealer, however.

“The color and type of siding is a factor,” explains Hilborn. “If the house is brick and is the same color, more or less, of the stain, stain overspray is not a problem. Stripping overspray is not a problem on brick. However, if the house has been painted white, both strippers and sealer or stain must be kept away from the painted surfaces.”

Finally, don’t forget to take a wide view when assessing the project prior to commencing work. “Sealer or stain can also land on the siding or the neighbor’s house or a car on the other side of the house,” says Hilborn. “All vehicles need to be parked indoors, including the neighbor’s.”


“It is our rule to protect from overspray on every single job,” says Meg Josetti, a principal at All Clean Power Washing, LLC in Selbyville, DE, which is owned by Bo Josetti. (Meg Josetti responds on behalf of herself and Bo Josetti.)

“For us, our roof mix is the most concentrated product in general,” says Josetti. And, again, water provides the key. “There is really only one way that we deal with overspray—and that is water,” says Josetti. Surrounding surfaces are watered down before soap application and immediately after soap application, she explains.

“In some cases, especially when we are doing a roof cleaning, we have at least one person water while the soap or chemical application is taking place,” says Josetti. On a large project, several employees may be watering simultaneously.

For the most part, says Josetti, plastic or tarps are not used to cover plants because of the danger posed to delicate plants on hot days. Moreover, she explains, washing surrounding plants with water would still be necessary following cleaning phase to reduce the ppm (parts per million) dilution of soap or chemical that will runoff into areas with vegetation.

Whether on a residential or commercial job, it’s a must to know what the customer expects before starting work. On residential sites, be sure to do a careful “reading of the customer and their expectations,” says Josetti. “If the customer voices concern regarding chemicals being an issue, sensitive to smell, etc.; if they feel they have very expensive ‘prize’ shrubbery; if the gutters and downspouts have anything unusual about them, we tend to take note,” says Josetti.

Explaining methods to residential customers can allay their concerns about overspray. The time taken to talk is a good investment.

A careful appraisal of a residential site prior to beginning a job also prevents claims for damage that a contractor did not cause, says Josetti. An ailing shrub should be documented in the proposal,and a homeowner should know what not to leave out during cleaning, such as chair cushions.

“If it is determined that there has been damage, always communicate to the customer that you will resolve the issue,” says Josetti. “Even in a case where you don’t agree with the claim, sometimes it is better to replace a $20 bush than to have an unhappy customer.”

What about a large expense for which the contractor is not at fault? “Be polite and document the issue and bring in a landscaper or other professional to consult on the situation,” says Josetti.

Commercial Projects

“There are additional factors that come into play on commercial jobs,” says Josetti, whose company cleans commercial office buildings, multi-unit residential buildings, storefronts, hospitals, assisted living facilities, and more.

“We communicate to the building manager or owner what we are doing so they can make sure the people that are in and around the building understand,” says Josetti. “We set up cones, signs, and caution tape for extra precaution.”

A thorough and complete proposal is where each commercial project begins, says Josetti. From that point forward, it’s “imperative” to be aware of weather conditions, especially wind, and how that could affect overspray, as well as every other relevant contingency, she explains.

Consider a health-care facility, says Josetti. In that setting, it’s particularly important for a contractor to know “where HVAC intakes are located and the direction of the wind,” she explains. And cones and signage to indicate wet areas are mandatory to prevent slips and falls.

“It is always important to make sure on every job that you are OSHA compliant regarding your soaps and chemicals,” says Josetti. “Safety data sheets should always be available and up to date.”

A safe environment is the goal of the contractor on every job, says Josetti. And part of creating a safe work environment is being prepared for the unexpected.

Hinderliter, Hilborn, and Josetti all share a deep commitment to professionalism and continuing education. An essential part of preventing against chemical overspray is knowing everything there is to know about the products being used in conjunction with water. “As a contractor, it is important to be educated and know your products,” says Josetti.