Power Washing and Roof Cleaning Forum

h2o spray · Approved Exterior Cleaner

1st Slate roof cleaning, advise please.

waxman18324 · Founding Member Rest in Peace

If you've cleaned asphalt I don't see you having any issue cleaning a slate roof. I can see the algae but is there any moss or lichen? We rinse our slate roof projects to insure all moss and lichen is gone. We use a 60/40 mix and never had a problem. I never used soap in my mix because that's how I was taught. Yes it will run down the roof quicker but I just leave the soap out. Others have used soap with success.

Hank

h2o spray · Approved Exterior Cleaner

Thanks Hank. There is a little moss and lichen but not a whole lot. (Couldn't get the picture due to tree) So a hot mix works for you, good to know. Is rinsing slate a must, or only your preferred process? I have heard horror stories where the SH turned the slate colors so I just wanted to get the basic rundown. Thanks again!

Maverick Contracting · Approved Exterior Cleaner

If it is very hot out temp wise, using SH straight may as it has plenty of times for me flash vaporize before having time to do anything. Even 12.5% uncut. Adding surfactant gave it badly needed dwell time.

I think the use of a soap surfactant discoloring the slate is due to too much and it's never been an issue in the 70-100 or so ive done. Its big in my area and the only time the surfactant left residue it washed off with a good rain.

If anyone has had long term effects of discoloration I'd love to see pics to see what I should be looking for.

Maverick Contracting · Approved Exterior Cleaner

I'm wondering if a high iron content or other reactive metal in the different types of slate may be what people are seeing as an issue?

I'd hate to see rust stains after a cleaning.
If that happened would/has a light acid treatment worked to remove the metal oxidation?

Michael Hickey · Approved Exterior Cleaner

We clean a lot of slate roofs without any problems. One expensive roof caused me to have cold sweat because there was a lot of green blobs on it after we cleaned it. Luckily for me my roofer James told me what it was. Copper in the slate. Panic attack over. I have read that there are oils in the slate and that soap takes the oil out does anyone know if this is true or not?

BlueRidge · Approved Exterior Cleaner

We have cleaned slate and never had a problem. At least a 50% mix with a little more soap and rinse. I have found in order to make it look really good you will need two applications so charge accordingly. You will also have to get downspout tubes so you can get the run off away from the house. Unless it's cool on the day of cleaning, pre wet the roof to cool it of and give your mix time to work. Even 70 degrees will warm up the roof.

h2o spray · Approved Exterior Cleaner

What soap is/is not recommended ? Just standard roof soap, or is there a specific soap for slate. Thanks for all that have replied!

Eric Schnaible · Approved Exterior Cleaner

I can't see any reason to not use a surfactant. At the very least it breaks down water tension and make your mix go much further, even with a small amount.

The most common staining that appears on slate after a cleaning is pyrite stains. These are generally not visible before the cleaning because the GM hides them. I tell customers before the cleaning that they may expect to see this after the cleaning. Then, instead of saying I caused it they think, Wow this guy knows his stuff. Check out the subheading "Pyrite Staining" on my slate page if you like.

Patrick G · Approved Exterior Cleaner

Bret here is a link to read, great print out to give to H/O prior ....learn the word " DELAMINATION "

www.nationalsoftwashalliance.com/t55268510/slate-roof-cleaning/

Steve Salley · Approved Exterior Cleaner

The discussion about delamination is very important. It will surprise you how much it has has occurred. You will not see it if the GM is heavy until after you clean the slate roof. The areas where the sun is reflected onto adjacent areas such as next to a dormer will be more apt to show delamination. the surface is double heated due to the reflection of the sun from the other roof sections plus the direct heat of the sun on those areas.

Relax, you can handle this with the advice of the many who have done slate roofs successfully. Yes, do charge for the service. Put it in perspective to the tens of thousands of dollars a slate roof costs to replace.

Be careful of your ladder placement. We choose to wrap our stabilizer bar ends to prevent any marring or pressure breaks that may happen to a slate tile.

Steve Sabella · Member

This is Edgemire Slate, cleaned it last week with 40/60 SH and slomo surfactant, came great!

Steve Sabella · Member

edgemire slate

Maverick Contracting · Approved Exterior Cleaner

Those are a concrete tile product but still have similar cleaning properties. Nice

Liberty SoftWash · PWS Vender

When cleaning slate we use a mix with no soap.

DirtyRoofcom · Approved Exterior Cleaner

I use basic roof mix with soap. little on the hotter side like others have said but not necessary. I do not rinse and have never had an issue with them not coming clean unless the roof was absolutely terrible b4 hand. Its hard to tell from the photos but roof doesnt look too bad. Id let them know about delamination before you start. Its either there or its not but by cleaning it you will uncover it and it will be more noticeable

This is a great project for your portfolio. if you can get a drone or a picture from a elevated position then do so. Make sure you charge accordingly. there is more risk w cleaning a slate roof on a home like that then your basic average ranch w asphalt.