EQUIPMENT USED FOR ROOF CLEANING PROCESS

Cleaning roofs, as we mentioned in earlier post, can be done in dozens of ways using many different cleaners and tools. As roof cleaning contractors, we want to use the method that keeps our material and labor costs as low as possible while producing results that our customers will appreciate and recommend to others. We also want to be safe, so minimizing the potential for injury is a very important consideration.

We have introduced the ideas of water brooms, surface cleaners, and using a pressure washer. We have also talked about ‘no pressure’ washing with strong cleaners that do all the work. Of all these methods, the safest, lowest cost method is to apply strong cleaners to a roof with a bleach-rated pump. This can be accomplished either from the ground or up on the roof (if you have the proper safety equipment).

While we cannot point to any single method as “the only way”, we know that the most successful contractors cleaning roofs today use strong cleaners and no pressure. The primary ingredient of that strong cleaner is sodium hypochlorite, or bleach. You must have the proper equipment for this technique. Here are some suggestions.

First, you have to arrive at the job ready to work. You can buy or build roof cleaning rigs that fit into the bed of a standard pickup truck, or you can use a trailer rig for this. Using a trailer frees your truck up for other duties, so that is the preferred rig.

Next, you will need a few extension ladders of differing lengths. On the job, you will always grab for the shortest ladder that will do the trick, because of the weight and clumsiness of carrying longer ladders.

You will need one or two detergent tanks. It is ideal if the tank intended for bleach is light-proof (either molded in an opaque color or painted) to delay the break-down of the bleach from sunlight.

The ideal size of your primary tank is 100-125 gallons. You are limited by DOT to carrying 1000 pounds or less of any strong caustic like bleach, and that usually comes down to a little under 125 gallons.

If you have one tank, you will premix your final cleaner (bleach and soap) in that one tank. If you have two tanks, the second one can be as small as 30 gallons and is used for the soap you will add to the bleach.

You will use about 60 gallons of this mix to clean a typical roof, so your 125-gallon tank should get you through two jobs before you have to go and refill.

Now to the more expensive parts. You need to purchase a chemical transfer pump that will handle bleach. Some pump manufacturers offer Santoprene-fitted electric pumps, which can hold up well against bleach for a fair amount of time. If you use an electric pump like this, you can use a 12-VDC source for power. This may be a battery or you may even tap your vehicle as a power source. Some pumps are available in 120 VAC configurations, but they require a generator for power and there is no appreciable advantage to using them. Pump failures have to be expected with electric pumps, primarily due to the corrosive nature of bleach. It is often wise to have a second pump standing by in case you need it.

Alternative transfer pumps are gas-driven and built entirely of stainless steel and poly, which are impervious to bleach.

The pump you choose should deliver between 4-8 GPM, or you will waste a lot of time. The pump is permanently mounted to your rig, so you need a long hose to deliver the cleaner to the roof surface. There are several choices in hose material, some being “bleach-rated” and some being just plain inexpensive enough to throw away when it starts being affected by the bleach. Bleach-rated hose sells for about $2/foot, while clear braided poly hose goes for as little as $0.50/foot.

The diameter of the hose can make a huge difference in the volume and throw-distance you achieve with your pump. Contractors use hose that is sized between 3/8” and ¾” and anywhere in between. There is little cost difference between various sizes, and it is suggested that ½” or 5/8” might be just right.

Length of the hose is affected by your target market, but most contractors look at either 200’ or 300’ as the perfect length. This amount should allow you to reach all sides of a typical dwelling in your area. Keep in mind that many upscale neighborhoods featured very detailed roofs with difficult areas to reach. It is always better to have too much hose than not enough. Avoid splicing this hose as much as possible, as every splice is a possible future leak. Leaks destroy your pump’s ability to deliver, and may result in property damage.

If you use poly-braid hose, it will begin to discolor and turn stiff within a few months. You will likely replace this hose annually. If you want to get the most out of your hose, we suggest using a hose reel. This can be any hose reel, but if it is made with stainless parts (at least the plumbing) then you will get longer life from both the reel and the hose. If you elect to work without a reel, you will be coiling up the hose each day after work. Eventually as the hose stiffens this task gets harder and harder.

You want the pattern of the chemical spray to stay as tight as possible. A wide ‘splashy’ pattern leads to chemicals reaching spots you didn’t intend to hit. Ideally, a small pattern around a foot in diameter is ideal. You may have to experiment a little to achieve the pattern you are looking for, but most people are successful using 0-degree shooter tips such as a 0040, 0050, or 0060.

Remember that plastic and stainless are not damaged by bleach, so make sure that your tip and gun are constructed of these materials. Some contractors build a gun using a ball valve, plastic pipe, and stainless nozzles. Variations abound, with most in favor of a bend downward at the end of the pipe. In stainless, this ‘bend’ is literally a bend in the tubing. In a plastic wand, a 45º fitting is added. Some dealers offer bleach-rated wands and guns already assembled for you.

Many contractors use a “multi-tip” tool that holds three or four assorted nozzles. This allows you to adjust your spray for conditions without having to look around for the last place you had that certain nozzle. They are all right at the end of your gun.

Among the miscellaneous items you will need to round out your equipment include a water hose and mixing buckets (if any part of your cleaning mix is in powder form). You may need rags, tarps to protect areas, light paper drop cloths for landscape plants, and other small items. Optional (but really nice to have) are things like ladder stand-offs (that allow you to place a ladder and climb it without hitting gutters) and a tool one manufacturer makes to continuously feed water to the gutters to keep the bleach from accumulating.

You should have whatever you need for contingency plans – in case you pump or hose fails or you get strong cleaner on an unintended surface.

Most importantly, you must invest in safety-related items. These include eye protection (like goggles or a face shield) and skin protection (rubber gloves, a face shield, etc.). You may want a rubber apron to wear when you are transferring chemicals, too. If you climb on to the roof to clean it you want that safety harness and possibly a portable anchor system that allows you free movement on the roof without the danger of an injurious or fatal fall. You also want Korkers or Cougar Paws for your feet to give you unbelievable traction on the slipper surface. Next, consider a respirator. Most strong chemicals will take your breath away, which is really scary up on a roof. Finally, you likely will want a waterproof pocket for carrying your cell phone, which can be your lifeline if you run into trouble.

THE ROOF CLEANING PROCESS

Washing a roof was generally considered a low-pressure contact sport in the “old days”. Before the creation of contemporary tools and techniques, you had to climb onto the roof with a pressure washer wand or a surface cleaner to get the job done. This involved significant risk of falls. If you use this method, be sure to use all appropriate safety gear when climbing on any roof. Never attempt cleaning a roof without taking all proper safety precautions; even the flattest roof can become slippery and hazardous when wet.

To clean a roof this difficult and dangerous old-fashioned way, you would drag the pressure washer hose or surface cleaner up on to the roof using a ladder. Moving around to reach areas was dangerous, since the slanted surface was soon covered with soapy cleaner.

Avoid walking on buckled shingles and avoid obviously sagging areas. On many older roofs you will be able to see where the roof joists are located, and putting your weight on these spots is likely to cause no damage whatsoever.

Look for cracks around roof projections (chimneys, vents, etc) and avoid getting water near these problem areas.

To walk on a roof, you should have safety rigging that meets OSHA guidelines. This will likely involve a body harness tied off to a structure on the opposite side of the home and shoes designed for walking roofs. This sort of equipment can be found at Safety stores. Many contractors still walk roofs to clean, but safety equipment is available now that was not available years ago that make the job easier and safer.

One company now makes a roof anchor that simply slips down into roof vent pipes, for example. This allows you to move around reasonably freely, secure from the danger of a fall to the ground. It is a lot smarter than tying off to the bumper of a vehicle (the source of many urban legends in this business).

If walking the roof does not excite you, there are at least two alternatives. One is to use a man-lift such as the one pictured here. You can spray the roof from this secure perch without danger of slipping.

Another alternative is to work from the ground or from the roof edge. It takes specialized equipment to make this technique effective, but this is the safest imaginable way to get the job done. We will explain all this in our upcoming posts. Commercial restorations roof cleaning process involves techniques which are safe and guarantee best results after cleaning is done.

ROOF CLEANING CHEMISTRY

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.

THE COMMON TYPES OF SOIL AND STAINS ON ROOFING

We have all seen roofs discolored and unattractive – covered with mold, algae, and bacteria. Like most issues affecting the integrity of a house, the problem goes much deeper than the unattractive appearance.

The gloeocapsa magma survives by eating minerals and excreting oxygen. The bacteria multiply rapidly by feeding on moisture and calcium carbonate (in the form of the limestone crystals used to manufacture asphalt shingles).

The problem has both spread and worsened dramatically during the last two decades. Internet research finds the main reasons cited for this worsening of the problem are:

1. The trend to rising humidity and temperatures (favorable conditions) has lead to increased reproduction (more spores)

2. Fiberglass shingles (the most commonly seen amongst today’s residential homes) are made with limestone as a filler (in the asphalt). These shingles hold moisture and organic “bacteria food” material longer (particularly on the north-side of the roof) than the paper/asphalt/ceramic shingles of 20 years ago. This is their food source.

Once the bacteria have taken hold of a roof surface that is favorable, it takes a significant amount of time before they become noticeable. From that stage, the visible evidence gets more noticeable every year until they take over the surface. This bacteria colony forms a tough outer shell for protection, and spends its days eating away at the infected roof.

It can be argued that there is little scientific evidence that these organisms cause actual harm to the roof. That is primarily because there is no financial support for creating a long term scientific study of the problem. The roofing manufacturing industry has no interest in proving to potential customers that there is no reason to replace their roof, for example. While this kind of study would help property owners make better decisions, it is really only financially valuable to you as a roof cleaner.

As contractors, we see the kind of damage done – up close. Common sense tells us that holding moisture in the shingles while breaking the shingles gown on a molecular level cannot help but contribute to the death of a roof. We see evidence every day of premature aging, rotting, and granule loss.

Shingles swell in thickness with this retained moisture. Most of the other visible damage is along the edges, where we see rounded and uneven edges, as well as curling. As the shingle degrades, it becomes a perfect host for further culprits, like algae and lichen. Once lichen appears, a roof may not even be salvageable.

This problem can appear at any time in the life cycle of a roof, even when the roof is relatively new. A shingle that might have lasted 20 years or 30 years if exposed only to weather may now become useless long before that time.

MOSS CONTROL

Roof moss is one of the other common reasons for roof cleaning. It has its own chemical solutions. Controlling the growth of moss is a potential service contractors can offer with seemingly no end of new customers.

Zinc Strips

Zinc strips are commonly used for a long-term solution to controlling mosses (see photo at right: skylights are surrounded by galvanized flashing that has suppressed the growth of mosses below the skylights). The remaining parts of this cedar shake roof are covered mainly with the moss Dicranoweisia. Zinc strips and galvanized flashing are apparently relatively safe and inexpensive. They effectively kill or retard the growth of mosses and fungi and appear to have effect up to 15 feet below the zinc flashing along the length of the flashing. Zinc strips are considered to be effective for up to one year, after which they can be replaced. The effect of galvanized flashing (example above) can persist for decades. Success rates vary with the degree of moss development and weather. Zinc strips or flashing are most effective before mosses are well developed. Physical removal of existing moss followed by installation of zinc strips or flashing is an effective long-term strategy for suppressing moss growth.

Negative Side Effects: Direct runoff from the zinc strips or flashing to surrounding vegetation, fish ponds, or water supplies should be avoided, because some contamination by zinc is likely to occur. Zinc strips should not be used with strong acids or bases (like bleach).

Zinc Sulfate

The active ingredient for most moss killers is zinc sulfate monohydrate – usually at concentrations of 99%. Zinc sulfate will not stain roofs or corrode aluminum and galvanized gutters. To use zinc sulfate one can apply powder directly to moss areas. Manufacturers recommend that powder should be applied at the rate of up to three pounds for every 600 square feet. For spraying combine three pounds to five gallons of water and apply to 600 square feet. This product needs to be applied on a calm day.

Powder application has been known to control mosses for two years and spraying application may need to be applied annually. Some roofing companies will guarantee no mosses for up to five years after using this product while treating roofs. Avoid runoff that can reach aquatic areas. Toxic to fish.

Zinc Chloride

Zinc chloride comes in two different concentrations, 13% and 62%. The 13% concentration can be applied directly to moss without mixing with water. Spray directly from nozzle six to ten inches away from target. Make sure to wet the area thoroughly. The 62% concentration needs to be mixed with water before applying to an affected area. Mix one pint of concentration to three gallons of water. Using a backpack sprayer, one manufacture recommends using one gallon for every 100 sq ft. Zinc chloride should be applied just prior to fall rains or in the early spring.

Zinc chloride is effective in controlling mosses from one year up to five years. Increased application concentrations may be needed in areas of higher moss concentration. Avoid drift and runoff when using this product. Zinc chloride will affect other plants and lawns. Application should only take place when air is still and when no rain is expected within 24 hours. Zinc chloride is corrosive and should not be used when copper fixtures are present. This product is toxic to fishes and aquatic invertebrates. Avoid contaminating water sources with zinc chloride. If zinc chloride comes into contact with a painted area damage is possible.

Zinc – Copper Sulfate mix

Zinc and copper sulfate comes dry, and can be applied as a powder or mixed with water. This product reacts electrolyticallly with water to stimulate a slow release reaction. Zinc and copper sulfate will not stain patios, decks, walls, walkways, buildings or roofs. However, zinc and copper sulfate may react with red bricks. This product is not harmful to lawns, ornamental shrubs, trees, turf or other vegetation such as flowers and vegetation. To apply simply sprinkle areas thoroughly with powder when it is wet, either after a rain or when early morning dew is present. Do not use this product in high wind. For spray application a wet applicator may need to be purchased. It is not clear if this product is still available commercially. According to information from one manufacturer, apply one pound of moss killer to 1000 sq ft. This product may be applied anytime during the year, but should not be applied while it is raining. Since this product specializes in the slow release reaction; allow plenty of time for the chemical to act. This product is corrosive and should not be used if copper fixtures are present.

Applications of zinc and copper sulfate are said to last for up to one year depending on the concentrations of moss. Annual application is generally needed. Though this product is supposedly safe for surrounding plants, it is still toxic to fishes and aquatic invertebrates. Do not apply this product to water or let the product come into contact with water sources. When applying this product or any product to rooftops it is essential to avoid runoff. Collecting the runoff would greatly reduce the negative effects on the environment.

Bleach

Chlorine bleach (sodium hypochlorite) can be used on a number of surfaces contaminated with mosses including decks, patios, walks and roofs. When used to proper concentrations bleach is non corrosive to metals and will not stain treated areas. One should, however, avoid contact with clothing. Brand names of bleach especially for mosses can be found in the moss control area in garden centers. Bleach is applied just as you do for roof cleaning, making this solution perfect for what you already plan on doing.

Bleach applications remain effective for up to one year, but annual applications are usually necessary. Bleach at these concentrations will be toxic to plants if left on for more than ten minutes. After ten minutes, injury or “burning” of foliage will occur. Since this product is toxic to fishes and aquatic invertebrates contact with water sources should be avoided.

WHAT DO WE CLEAN FROM A ROOF?

When you pull up to a house one of the first things you notice is how stained or discolored a roof is. Some people will want their roofs cleaned merely for aesthetic reasons while others are looking to extend the life of their roof. As we stated earlier, as much as 50% of all roof replacements have been done because of the appearance of the roof and not actually because of its functionality.

How much is spent on a roof? $5,000, $10,000, $20,000, or even more? Whatever your reason for roof cleaning that is a huge investment to protect. If you can extend the life of a roof, you delay the cost of roof replacement.

Cleaning residential and commercial roofing has become one of the best profit centers of the exterior cleaning business over the last decade. This is due to two factors: the fast spread of the contributing algae problem from warm, humid climates in the southeast to the north and west; and secondly due to the touch-less cleaning techniques that came out of Florida over the last couple of decades.

We will be discussing causation and the wide array of solutions and techniques used to combat the problem. Just as in every other element of cleaning, there is no single way to achieve acceptable results – there are many ways to get the job done.

No matter how you end up cleaning roofs, there are basic things you should understand about roofs before you ever decide to tackle a job. If you are going to walk on a roof, for example, you had better know how that roof is constructed and where you can put your feet and still be safe. If a roof is close to failing due to age or abuse, you should be aware of that before you commit to do the work.

We will begin with discussing what is causing all of the problems and then move on to the most popular and profitable techniques used today. When cleaning a roof it is important to identify what we are cleaning and removing as well as how to perform these jobs.. Before we do let’s discuss just what is on the roof!

Cyanobacteria or Cyan Bacteria – One of the most common items is a type of over 20,000 types of algae that is not related to other algal groups, Cyanobacteria or Cyan Bacteria. Despite the name, Cyanobacteria does not have decomposing properties. It acxtually contains chlorophyll which traps the energy from the sunlight allowing it to grow anywhere. Cyanobacteria are capable of surviving in extreme conditions and have been found in deserts as well as Antarctica. Cyanobacteria have been found on polar bears and can give off a green hue to the polar bear’s coat.

Gloeocapsa Magma – a bacteria that appears on many roof tops that appears often as black or greenish streaks. It thrives on limestone and calcium carbonate that is a structural part of shingles. Moisture is critical, so this bacteria forms a hard surface that retains moisture. This is why these streaks are usually prevalent on the north side of the roof more shielded from the sun or areas under trees. It degrades the shingles over time. Slowing or stopping the deterioration will extend the longevity of the roof.

Lichens – Lichens are not single organisms the way most other living things are, but rather it is a combination of two organisms which live together. Most of the lichen is composed of a fungus, but living among the filaments are algal cells, usually from a green algae or a cyanobacterium. In many cases the fungus and the algae which together make the lichen may each be found living in nature without its partner, but many other lichens include a fungus which cannot survive on its own — it has become dependent on its algal partner for survival.

Moss – Mosses are very small green plants. Typically they consist of a stem not much thicker than a thick hair, densely covered with leaves maybe 1/16th or 1/8th of an inch long. Often moss stems branch and rebranch. Usually many mosses grow together forming a thick green carpet. Sometimes this carpet is no larger than a dime, but other times it may cover areas several feet in diameter. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems.

WHY CLEAN ANY ROOF?

There are many reasons for cleaning roof. Some of the most important ones are listed below:

1) Left untreated, the roof will begin to fail within a few years.

2) Left untreated, the roof will absorb excessive heat, taxing A/C systems and raising utility costs.

3) You can help them get the maximum life expectancy of the roof, without damaging it.

4) You can clean the roof at a fraction of the cost of replacing the roof.

5) You can drastically improve the curb appeal of their home. This is expecially important if the property owner is planning on selling their home!

CONSTRUCTION BASICS FOR ROOF CLEANING

Since the primary target for roof cleaning work is the residential market, we are going to look at typical home construction to introduce roof safety and roof etiquette.

It’s important that you understand the basics of roof construction before you think about doing this work. If not, you may cause leaks and severe damage to the home – or even hurt yourself. Most power washers use machines capable of pumping 4-8 gallons of water per minute, and one mistake can cause thousands in damage, for example.

Most roofing materials are installed over a layer of felt paper and in some cases a rubber like ice guard material. The felt paper is installed over plywood sheathing, which is nailed to the rafters every 24” (varies by local codes). Sometimes you can see where the rafters are because they form almost invisible ribs on the roof. This is a sign of aging, indicating that the plywood is sagging ever so slightly in between the rafters.

The first layer of shingles is called the starter course and is installed at the lowest point on the roof, upper-side pointed down. This allows a solid base for water to run over without leaking down into the rafters and plywood between the shingle keyways. Once this starter course is installed another shingle is place directly on top of it, and the rest of the roofing is placed in a similar fashion up the roofline. The reason shingles are installed in this manner is to allow the water to run over one shingle onto the next until it enters the gutter system.

If the system for roof cleaning that you adopt involves walking the roof, it is critically important that you objectively look at the roof for signs of weak spots. There may not be any leaks appearing in an old roof, but all it might take is walking around on the wrong spots to make the situation arise. Look for any sagging areas, as that indicates a weakness in the plywood. Stepping on a weak spot like that could end up causing you to drop through the roof to the attic below.

If you walk a roof, limit your footsteps to the rafters if at all possible. As an alternative, many contractors use walking boards they can move around. Stepping on a board spreads your weight over the size of the board instead of just the size of your shoe.

Now that you understand the basics of roof construction it’s equally important to know the other structures on the roof and their function to avoid causing leaks around them.

Vent Pipes – Vent pipes are used to vent gasses from plumbing fixtures in the home. They have a rubber gasket around them that wraps tightly around the protruding pipe to keep out water. Inspect all vent pipes to make sure there are no cracks or tears in them.

Flashing – Flashing will be found where chimneys and other objects meet the roofing. It should be fastened and sealed in place to keep water from entering the home when it runs down the surface.

Ridge Vents or Peaks – This picture shows the peak of a roof with the ridge vent removed so you can see where any water entering it will enter the home.

Nail Pops – Nail pops may only be small holes in the roofing but they can allow water into the home and under the shingles and felt paper. When water gets under the tar paper it can become trapped and cause the plywood underneath to rot.

Skylights – Skylights may be found on many roofs and require extra caution. Never spray water around them, as they will usually leak if you do.

Powered Attic Vents and Missing Shingles – Most homes have motor driven vents on their roofs to remove excess heat on hot summer days. If water is sprayed under these vents it can easily run down the wires causing a short in the electrical system or a fire. Obviously it’s also important to make sure there are no missing shingles before you begin washing the roof. All of these items can easily be fixed by an experienced roofer but its imperative that they are fixed before you clean the roof!

TILE, METAL AND MEMBRANE ROOFS

Asphalt roof type was discussed in our previos blog post. In this post we would be discussing some more roof types namely tile roofs, metal roofs and membrane roofs.

TILE ROOFS

Here is an example of clay barrel tiles used for roofing. This is a popular look in states that border Mexico and the Gulf.

The manufacture of tile roofing is represented by the Tile Roofing Institute, whose web page is www.tileroofing.org

Clay tile is produced by baking molded clay into tile. The density of the clay is determined by the length of time and temperature at which it is heated. Tiles may be glazed and also may have surface texture treatments applied. As a result, there are a wide variety of tile profiles, styles, finishes and colors available. In addition, each tile may have separate field, ridge, hip, gable and terminal tiles of various shapes. Installation methods depend on the nature of the tile being installed; that is, whether it is two piece, one piece, interlocking or flat.

Concrete tiles are made of portland cement, sand and water in varying proportions. The material is mixed and extruded on molds under high pressure. The exposed surface of a tile may be finished with cementitious material colored with synthetic oxide additives. The tiles are cured to reach the required strength. They generally have lugs on their undersides for anchoring to batten strips. There are additional waterlocks or interlocking ribs on the longitudinal edges that impede movement and prevent water infiltration. As with clay tile, there are a wide variety of profiles, styles, finishes and colors available. Color may be added to the surface of a tile or dispersed throughout (color through). Special texture may be added in surface treatment.

The TRI does not suggest any particular cleaning method, but they reference the fact that cleaning may be necessary. A check of some manufacturers finds instructions like: What is the best solution to use forcleaning roof tile? Common household bleach at no more than 1% strength should kill most of the algae spores.

Contractors have tried to clean using solutions of just 1% concentration without good results. Repeating what we said before, we find we can make a solution in the range of 3%-6% concentration and have an effective cleaner without altering the integrity of a tile roof.

The other element to creating a cleaning solution like this is that it should contain some soap. We strongly suggest that adding a surfactant (detergent) to your roof cleaning solution will minimize how much of that solution you have to use overall.

METAL ROOFS

The Metal Construction Association (www.metalconstruction.org) promotes metal roofing. They certify properly manufactured roofing panels. The Metal Roofing Alliance (www.metalroofing.com) also promotes metal roofing materials for residential and commercial use.

Typical metal roofs are either shingles or panels, and may be bare or painted. The most common metal roofing consists of metal panels that are painted in an architectural color.

The drawback to cleaning a painted roof comes from the paint itself. Paint subjected to intense sunlight and pollution may fade, pit, or discolor. Since any algae or soil on the surface of the paint cannot root down into the paint, we found that lighter concentrations of bleach and soap (in the range of .5% – 1.0% sodium hypochlorite) gives the best cleaning with the least amount of risk to the paint.

Copper roofs are different. The most common complaint about the appearance of copper roofing is about ‘patina’ or fingerprints, and acid-based cleaners are excellent for restoring the original look of copper.

MEMBRANE ROOFS

Membranes are sheets of flexible rubber-like material used for roofing. Limited to mostly flat industrial roofing where the membrane is covered with stone, membrane roofs are rarely cleaned.

SLATE ROOFING

The National Slate Association (http://slateassociation.org/) is a resource for roofing professionals, architects, builders and property owners for slate roofing materials. Since slate roofing is made from metamorphic rock, it will not saturate with water, and it is completely fireproof, making it a great material for homes in areas subject to wildfires. Since it is a natural stone it also has extremely long life expectancy, as long as 100 years!

There are many other types of roofing materials used in construction today, but regardless of what they are made of, all of them can become a breeding ground for mold and algae growth.