Got a 10 year old 'mud porch' slab 10x10. Until this past season, never much issue; lately, considerable spotting of darker mottling with some areas of greenish ultra thin layer of unidentified growth.

Repeated applications of various bleach forumlas, home chemicals, wire brush etc, have not prevented return.

Any concrete coatings that are good for prevention, non slippery. This is a walking surface, partially exposed to sunlight part of the day.

This message has been edited. Last edited by: signewt,

You might want to try Wet & Forget, a product that Costco sells. Just spray it on, it can take a few weeks, but all of a sudden you notice the mold is gone. I believe Wal-Mart and Amazon also sell it.

I do this on a commercial scale think parking garages, and office buildings.
I would recommend a through cleaning with a power washer, and an application of an epoxy coating. The products I normally use are borderline cost prohibitive for your size slab. A 10 gallon kit covers about 350 square feet. And costs about $500.
If you would like I can reach out to some product reps for a recommendation on product.
Only thing I need to know is if the slab is on grade or elevated.
My email is in my profile. I’d also be happy to walk you through all the steps necessary for a proper and successful application.

total area is around 100+ sq feet; setting on low gravel substrate at near ground level;

something on the order of "Wet & Forget" sounds like the next step in our battle as our battle to 'remove' has been somewhat successful.

The next step is some kind of moss/mold resistant coating/ that stands up to foot traffic/rain/mold attacks. Epoxy coating will need to read further for such.

$500 is well beyond the budget.

ffemt44 is the expert... I'd pressure wash the heck out of it and forgo 'cheap' chemicals... sounds like an epoxy coating is the answer... there should be a way to get a smaller amount of some good stuff... 10x10 is not that big an area, heck it might be easier just to buy a pressure washer and wash it every month or so.

quote:

Originally posted by signewt:
total area is around 100+ sq feet; setting on low gravel substrate at near ground level;

something on the order of "Wet & Forget" sounds like the next step in our battle as our battle to 'remove' has been somewhat successful.

The next step is some kind of moss/mold resistant coating/ that stands up to foot traffic/rain/mold attacks. Epoxy coating will need to read further for such.

$500 is well beyond the budget.

Let me make some calls today and see what I can find for your application. Most epoxies are not used in slab on grade applications as water leeches through the slab and DeBonds the epoxy. For 100 square feet I may be able to talk to a couple of my reps and find you the right product as a “sample” . Do you have a budget you would like to stick to?

ffemt44:

will email you this afternoon with further discussion, thanks

Just rent a power washer for $40 and blast it away every other year. No biggie. You can power wash lots of other stuff around the house too while you're at it.

quote:

Originally posted by rtquig:
You might want to try Wet & Forget, a product that Costco sells. Just spray it on, it can take a few weeks, but all of a sudden you notice the mold is gone. I believe Wal-Mart and Amazon also sell it.

I am hoping this works.
I had some serious mildew on the siding of my cabin and water pressure is far too low to accommodate my pressure washer so I tried wet & forget.
Sprayed it on in November when I closed it up for the winter. Looking forward to seeing if it worked in a couple months when the weather breaks.

As for the issue at hand I pressure wash my driveway and concrete patio each spring.
Does just fine.

-Plural component (solvent based) epoxy coatings don't lend themselves to exterior applications where UV rays will be an issue.
-At the spread rates quoted you can expect a somewhat slippery surface when wet or icy.
-Moisture transfer will be nil and the coating can and often bubbles or de-laminates on exposed exterior applications.
-Significant prep is required and epoxy application is a hassle for the benefits you can expect.

Get you a power washer and blast away. You will be far ahead.

considerable results now evident after last wire brush/secret component fluid solution and pressure spray....

given the physical setting, it looks like the pressure spray solution is going to be adequate without exploring epoxy/etc coating;

Thanks for suggestion one and all.

Subject is now adequately resolved.