We have introduced some elements of roof cleaning in or blog post about construction basics for roof cleaning, such as the idea that you might walk the roof in the cleaning process. It is time to drill down and talk about the advantages and disadvantages of all the options in front of you.
First, let’s discuss cleaning solutions. We have introduced the idea of using sodium hypochlorite as the base of your formula. In actuality, many different chemicals gave been widely used to clean roofs. In addition to bleach, sodium hydroxide, potassium hydroxide, calcium chloride, and percarbonate cleaners are each commonly used. None of those cleaners is as aggressive (or as corrosive) as bleach.
Sodium hydroxide will kill the algae and remove the soil off any roof, but typically requires the use of more physical agitation than sodium hypochlorite. That agitation can come in the form of a surface cleaner, pressure from a power washer, or a simple scrub brush. Sodium hydroxide is best for a roof that is walk-able, because the pressure needed is frequently less than 500 PSI controlled by a person who can see if any damage is being caused. Visible damage usually consists of the granules being abraded off the surface of the shingle. Some contractors prefer using sodium hydroxide because it seldom causes problems with adjacent plant life or latex paint.
Potassium hydroxide behaves similarly to sodium hydroxide on a roof. Potassium hydroxide is used when animal fats are present, as may be the case on the roof of a fast-food restaurant.
Calcium chloride is a chemical powder usually referred to as “pool bleach”. It cleans somewhat closely to the way sodium hypochlorite does, but comes with some special problems all its own. It frequently leaves a white haze over the entire surface that cannot be easily rinsed off. The benefit of this cleaner is how easy it is to transport and handle. Until someone develops a variation on this chemical that eliminates the white haze, it is impractical to use it for roof cleaning.
Percarbonate cleaners and hydrogen peroxide are the least aggressive cleaners available. They either require extensive dwell time or excessive abrasive force to be effective. Many of these cleaners are packaged for casual or DIY use because they really can’t harm anything.
In the end, what most contractors who are profitable doing roof cleaning have found is that using bleach is the fastest and most effective way to clean a roof. If you use bleach properly, you will be able to clean dozens of roofs each week and make money on every one of them. It is imperative, therefore, that you learn how to use bleach properly.
Bleach is susceptible to both sunlight and heat. Either of those will break down the chemistry of bleach relatively quickly – in a matter of days.
The first rule: Only buy the amount you can use in a reasonably short period of time. The length of time is determined by how well you can take care of the bleach. If you have light-proof containers in cool storage areas, you may be able to hold bleach for a month. If you are going to keep it on your trailer in a semi-clear jug, you may only be able to hold bleach for a couple of days.
The second rule: Buy fresh bleach. Bleach purchased from a chemical supplier is usually not a problem, but bleach bought from a store where it may have been sitting for several months is often a waste of time and money. If you are buying bleach from a grocery store, go to the store that moves the most product every week. A Wal-Mart is an excellent place to shop for fresh bleach, for example. What you are buying at a place like Big Lots is more like water than bleach.
Fresh bleach from a grocery store is likely a 5.75% concentration. This number is extremely important to you. Most contactors clean roofs with a concentration between 3% and 6%. If you are starting out with 5.75%, you might find you must use it straight or almost straight to get the cleaning effect you are looking for.
Some contractors are able to purchase industrial bleach at concentrations between 10% and 15%. This opens up their options. There is no appreciable difference between bleach bought at a grocery store and industrial bleach except the concentration (and the cost per usable gallon).
If you buy a gallon of 12.5% bleach, you have exactly the same cleaning power as 2.2 gallons of 5.75% bleach. If the 12.5% bleach costs you $3/gallon and the 5.75% bleach costs you $3/gallon, you are getting 2.2 times the cleaning power for the same dollar amount. That is the most common reason for purchasing industrial bleach.
If you can’t get industrial bleach in your area, use ordinary bleach. It is the same product.
The only other reason why industrial bleach may be more advantageous to use is the limit placed on how much chemical volume you are allowed to carry on your vehicle. The DOT and other government agencies limit you to 1000 pounds of any strong alkaline or acid on your vehicle. In liquid, that means somewhere around 100-125 gallons is all you can carry. A gallon of industrial bleach contains 2.2 times the amount of cleaning power as regular bleach, so carrying 100 gallons of industrial bleach is as valuable to you as carrying 220 gallons of regular bleach.
Assuming you have made the decision to use bleach as your cleaning agent, you next have to consider a soap to add to it. The purposes of adding soap are manifold: to add cling, to provide lift for any soil loosened, to cover the sharp odor of bleach, to activate the cleaning power of the bleach, and on and on.
Select a high-sudsing detergent to maximize the cling effect. You want the bleach to stay on the pitched surface long enough to be effective. The stuff that runs down the roof and into the gutter is almost wasted, while the stuff that sits there a while is doing all the work. The detergent you choose must be bleach-compatible, too. Read the MSDS of the soap you intend to use for a pH between 7 and 14 before you decide to mix it with bleach. The better the detergent is that you add, the lower the concentration of bleach has to be.
Most detergent agents are attacked by bleach (chemically) and after several hours may no longer work as well as when they are freshly mixed. Sometimes they produce a sour odor not associated with “clean”. Therefore, whatever soap you decide to add should be added only as needed to make a cleaner you intend to use within hours.
Laundry detergents and dish detergents are famous for being low-sudsing formulae. Car wash detergents are high-sudsing. A little experimentation will result in a soap that works well for you.
Finally, a lot of folks will add other things to the mix to make it their own. The most common addition is TSP, which adds to the alkalinity but doesn’t really help the overall cleaning process. Phosphates are banned in many areas as well. Don’t be fooled into thinking that your roof mix won’t work because you didn’t add TSP. If your roof mix doesn’t work, then the bleach you have is likely no good. As long as the bleach is fresh, it will work for you whether or not you add anything else.