Should we pressure wash roofs???????

Ron Musgraves

Ron Musgraves

Exterior Restoration Specialist
Staff member
yes we should wash roofs, but only if you know what your doing. Its real easy to do damage. And yes bleach works just fine no matter what some say. heres the proof, this roof is 15 years old and i did it with a 3200psi 5.6 gpm hot water machine using a 2510 nozzel to reduce pressure.
 

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Chuck I probably would feel comfortable only using a 12-15 size tip on your machine, which would reduce the pressure to less than 1000 psi. I tried doing some (nasty) roofs earlier this year and found this to take too long. I tried 4 different chemical combinations, including New Again and bleach. In summary, on the roofs tried I would need to use pressures closer to what you are using to make a profit, but don't feel comfortable with that - although I am not saying you should feel the same.

Ron, the NaOH issue is the other reason I decided to not clean roofs. Until I can find a good third party technical study that shows the effect of treating shingles with bleach or NaOH, I'll do something else.
 
My two cents on roofs

Use pressure when needed, other wise I have used just a fan off a hose... But there is times that you have to use heat and some pressure... Chuck is right bleach is fine and that is what I use,
well a strong house wash, but then again we dont have the mold problem like down south... Walter out of W.V told me his home brew and it worked great... I wish ole Walter would come back!!!


Matt
 
if ive said it

once ive said it 1000 times.
Chems do the cleaning and pressure just help's wash it away.
If pressure is trying to do your cleaning then your damageing the surface.
There may be some exceptions, like soda blasting,gum removal,stuff that's bonded to the surface,ect...
but not roofs.
 
i'v been doing roofs for 4 years and have never once had a problem. I don't stick the nozzel up against the shingle, i'm usally anywhere from 3'' to 8'' away from the surface. I can do an average size roof in 2 hours or less. If you relied on chemicals alone to clean the black streaks from a roof it would never get clean, trust me. I know everyone has their own opinions but i gaurentee any of yall that are uncomferible doing roofs come down my way and i'll have taking every roof job that comes your way.
 
Washing Roofs

In FL 99% of my work is roof cleaning. Yes we do use chlorine on barrel tile roofs everyday. We take care of the plants by properly covering and rinsing constantly. It is the most cost effective and fastest way to remove the mold problem. On shingle roofs we use chlorine also and it works. Pressure removes the granuals and takes away part of the life of the shingle. Most weekend warriors will PW a roof and take off most of the granuals. The other products are too expensive to make any money on barrel tile roofs. Product is only 69 cents a gallon. I understand the harzards to the ecosystem but will be open to safer cost effective methods. Jim
 
I can wash a 15 year old roof with pressure and not remove the granuals, how come everyone else has such a problem with this? If you know what your doing you will not cause damage.

Mr. Twist i use pressure on roofs and i do this full time. Would a weekend warrior have a rig like this?
 

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I agree with Chuck. Using the correct chemical, dwell time, and pressure you can clean an asphalt shingle roof with very MINIMAL granular loss.

My only variation is that I am not a believer in nor do we use Bleach or Chlorine to clean roofs. And those that do, use some amount of pressure and also cause some amount granular loss.

I have read serveral the ASMA's bulletin regarding soduim hydroclorite and attempted to speak with someone who creates the bulletins without success. They also state in another bulletin that algae is only an eyesore and does not harm shingles. I know I myself have sold a few jobs based on what ASMA now calls a myth.

Fact, the members of ASMA make money by selling shingles not by cleaning them. Besides water pressure, roofs endure other damaging elements such as heatwaves, acid rain, and ultraviolet light. Which is worse? I sure would like to see a comparision. But until then I don't preach ASMA bulletins like the bible.

All in all, if you are honest with your customers, educating them on the methods available and tell them why you choose a particular method it will ultimately be up to them to make the decision on what contractor to use.

In addition to being honest with customers, a contractor must also be knowledgable of what he/she is bidding. Of course a roof that has a 20 year shingle with 3 years left on it is more a canidate for granular loss then a 25 year with 12 years left.

However, my company does not clean any roof that has expired more than 75% of its life. Most importantly, I wouldn't recommend either method for roofs of this age. But that's just me and not a industry standard.

In conclusion, until someone can show me documentation or a study that states that the Low Pressure (< 1000psi) method takes years of the life off a healthy roof (> 25% of life remaining), my company will continue to use the low pressure method.
 
We try to avoid any type of pressure on roofs. Most of our customers also insist on cleaning the roof without ANY pressure. We generally clean shingle, clay (barrel) tile, and concrete tile roofs – and we don’t use any kind of pressure on any of them. Most of the major property managers we deal with are now insisting on no bleach, no pressure, and no walking on the roofs – primarily because of the damage that has been caused by other companies in the past.

When we are cleaning shingle roofs, we typically use chlorine and water - if the property owner or managers needs to have immediate results, but we never use anything more than a soap tip 12-18" from the surface at 4gpm to rinse. Even at that pressure, I have always seen a loss of granules – with newer roofs, it’s not as significant as it is with older roofs, but granules are still being lost.

I have not seen any recent studies, but it seems relatively obvious to me that repeated use of any kind of chemical that might dry out the shingle (like chlorine or sodium hydroxide) combined with repeated high-volume rinsing will accelerate the aging of the shingles and shorten their expected life.
 
Coastal:

If you are not using chlorine, what are you using?
 
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