Power Washing and Roof Cleaning Forum

Nikolas153 · Member

Concrete tile roof cleaning problem.

Zach Maynard · Approved Exterior Cleaner

The white spots look like Lichen to me, which can be killed using SH. (if that's what it is)

Nikolas153 · Member

I wish it was the Lichen, but I don't think so. I tried strong acids and SH too - nothing works, only pressure washing.

Jeff Wible · Approved Exterior Cleaner

I'm with Zach,..I think it's lichen,..especially the way the "grouping" looks. Just looks like typical lichen. What makes you think SH isn't working? Because of it's light color,..lichen doesn't show as dramatic reaction to SH as other molds and/or moss type growth. And it isn't gonna disappear upon application.

Jeff

Eric Schnaible · Approved Exterior Cleaner

Jeff Wible wrote:
I'm with Zach,..I think it's lichen,..especially the way the "grouping" looks. Just looks like typical lichen. What makes you think SH isn't working? Because of it's light color,..lichen doesn't show as dramatic reaction to SH as other molds and/or moss type growth. And it isn't gonna disappear upon application.

Jeff

Yes, what Jeff said. We run in to that lichen all the time. The SH definitely kills it. It just doesn't change much visually. Give it time. Any dark bacteria stains should be gone though.

Nikolas153 · Member

Jeff,
two reasons why I think it is not Lichen:
1) It does looks like calcium buildup from concrete tiles and it is very strong.
2) I tried 3% SH solution on it, waited for one hour, then rinse it off with water - no results
If it is Lichen, maybe I should try stronger SH solution?
My costumer wants instant result, it means by the time I finish cleaning white spots should be gone without using pressure washer on the roof.

Eric,
How long should I wait after SH application? I have to find the way to completely clean it by the time I am finishing project.

Thank you.

Eric Schnaible · Approved Exterior Cleaner

If it's lichen, you should be able to manually remove, brush/scrape it off. Is it actually hard like efflorescence build up? Any chance it bird turds?

Jeff Wible · Approved Exterior Cleaner

3% isn't gonna touch lichen. That's nothing more than glorified house wash mix. It needs to be zapped really good to kill it dead. When a customer WANTS instant results,..be sure they pay for those instant results. Remember,..it's not your fault the roof is in the condition it's in,.and the customer can pay for what it takes to get those results.

Jeff

BlueRidge · Approved Exterior Cleaner

Jeff Wible wrote:
3% isn't gonna touch lichen. That's nothing more than glorified house wash mix. It needs to be zapped really good to kill it dead. When a customer WANTS instant results,..be sure they pay for those instant results. Remember,..it's not your fault the roof is in the condition it's in,.and the customer can pay for what it takes to get those results.

Jeff

Nikolas153 · Member

Unfortunately it's not the bird stuff.
Jeff, thank you for your suggestion. What percentage do you think I can use to clean it at the same day? assuming customer is ok to pay.
And why strong Muriatic Acid didn't work?

Eric Schnaible · Approved Exterior Cleaner

I figured 3% meant 30%, Which should do the trick.

This is probably stating the obvious for most but I'm throwing it out there for clarity.
Most of us receive our SH at 12.5%. subtract 2.5% for any loss of strength for multiple reasons. (and because it makes for simple math). That gives you a standard working strength of 10% SH. A standard roof mix is 30%. The actual % of pure SH would 3%.

These percentages also sound better when the homeowner says, "Is that bleach?". "Yes Ma'am, our solution contains 1%-3% bleach". That doesn't sound so bad. And if they think they found our "Secret", their 3% household Clorox will never work.

On another note. I wouldn't use muriatic acid on concrete tile if I were you. Thats just me.

Jeff Wible · Approved Exterior Cleaner

For just black streaks 3% will work,..although I'm still at about 4-5%. But lichen needs zapped really good to make it loosen it's hold so it can fall away. Even with just black streaks,.. I'd rather spray a little less total mix than have to spray more times with a lighter mix. Pitch of the roof can also play a role in the strength I use. Now,,on a cement tile roof or slate,.and if I'm dealing with lichen,...that I want soft enough to (Hopefully) rinse away without having to be directly on it,...I'd be at about 5-6%,..along with some NAOH added for extra punch. The cement will handle the NAOH,.where asphalt shingles will not. But NAOH will compliment SH very well in this situation and help the softening. Use extra surfactant so it hangs onto the lichen allowing the mix to penetrate into it.

*But, nothing is gonna be able to be sprayed onto the lichen and have it just go away. So,.if you have access to the lichen,..just use regular roof mix and remove it with your washer.

** Erics right,..muriatic acid on cement shingles could darken them or even remove the top finish,..if it's still there.

Jeff

Fred W · Guru

3% works just fine in our neck of the woods for Lichen.

Eric Schnaible · Approved Exterior Cleaner

Yeah, for us too. In my area we have quite a diversity with lichen and algae types. Some are very hardy and tenacious. As mentioned earlier by Jeff, they really don't change much visually when hit with the juice. We also have certain types of lichen that grow great where zinc leaches from sheet metal. Zinc usually keeps those areas clean. Its kind of silver, white, light green. I'll post some photos when I get back from England in a week.

Jeff Wible · Approved Exterior Cleaner

3% will work,..considering he is going to PW it off. But for easier removal and "instant" results cleaning,... (Like he's wanting to do here),....a stronger mix is always better,..especially for hard to rinse areas,..where you may not be able to get right on it. It breaks the lichen down and softens it which allows for easier rinsing. .

Jeff

-- Edited by Jeff Wible on Thursday 10th of August 2017 03:24:32 PM

Fred W · Guru

In our area we just don't need to go stronger Jeff. 3% takes care of it really well.

Nikolas153 · Member

Thank you for suggestions.
I will try stronger mix on my next project, and see how it goes.

Jeff Wible · Approved Exterior Cleaner

Baton Rouge Roof Cleaner wrote:
In our area we just don't need to go stronger Jeff. 3% takes care of it really well.

I think the difference may be in the strength of the SH we get,.yours may be stronger? Either way though,.if he's PW'ing off a basic mix will work.

Jeff

Fred W · Guru

We buy it at 12.5% but I do know it comes in stronger at times. I used to get a printout when I used Univar and from them we usually ran close to 13%

Cleanupcrew · Veteran Member

From a job last week.

They are terra cotta clay tiles that get bad with lichen.

A couple of hits with 3% SH makes it so much easier to pw it off.

DirtyRoofcom · Approved Exterior Cleaner

customer wants instant results...... HAHA but waited years to clean the roof