Thursday, August 29, 2013

Corte Composite Deck Cleaner Review

Three years ago we built a composite deck (TimberTech).  I guess I thought low maintenance meant no maintenance, so I hadn't done anything to the deck since it was built. It's been nice not having to worry about staining or painting it.  Earlier this spring, I noticed black spots on the deck, which began to grow and multiply until it ended up looking like this:

After doing some research on the internet I discovered many people have had problems with black mold forming on their composite decks. Some have had great difficulty removing it.  I decided to try Corte Composite Cleaner based on the reviews I had seen and the fact that it appears several composite manufacturers recommend it.  

The product got more than its share of negative reviews on, which was made me concerned.  However, I realized the manufacturer says to not use the product beyond its expiration date, otherwise you might not get satisfactory results.  My guess is some gray marketers were putting old product on Amazon.  I decided to buy from the manufacturer's website to ensure I got a fresh batch.  However, with Labor Day weekend coming up and guests coming over, I decided I needed to get the deck done now.  I called the manufacturer and found a retailer fairly close to me.  That retailer said they had just gotten a shipment last week.  The expiration date on the bag I bought is August 2014 one year from this month.  So, the product does not have an extremely long shelf life.  I recommend making sure you get a fresh bag.

To do the project I needed:

  • Mixing bucket- already had
  • 1 gallon pump spray- picked up for $10 at the local hardware store
  • Deck brush- a scrub brush on a handle to save your back. $7 at the local hardware store
  • Corte Cleaner- $30

The product is a white powder that you mix with water.  It reminded me of trying to use Oxi-Clean.  It was not easy to mix.  I tried it first with room temperature tap water. For my second batch, I used warm water.  I stirred and stirred and stirred and could not get all the crystals to dissolve.  I began by hosing down the deck and going over it lightly with my brush to get the loose dirt off.  To my (pleasant) surprise a great deal of the dirt/mold came off with just plain water.  In fact, my wife came out and commented on how great the product was working and I hadn't applied it yet.

I let the deck dry, per the manufacturer's instructions and began spraying the Corte Clean on.  Using the fine sprayer I had, the product was more than enough to cover the recommended square footage.  It went on kind of like dishwater- slightly soapy and as it reacted, began to foam up, reminding me of oven cleaner.  I reapplied the product as necessary to keep it wet while I waited the 20 minutes for it to do its thing. To my surprise I could see the dirt being lifted out of the wood as the suds went from white to brown.

After approximately 20 minutes, I hit the deck with the brush again.  I wanted to be sure I got as much of this gunk off/out as possible.  Then, I began rinsing. As I rinsed, I could see the dirt flowing off with the water. Rinsing took forever.  I rinsed and rinsed and rinsed.  Now it was about 95ยบ the day I was doing this and I did it in full sun.  The manufacturer recommended doing it in the sun, but not at that temperature.  I don't know if that had anything to do with it or not.  Each time it would let it dry completely I'd see a bit of white haze, not horrible, but enough I wanted it off.  However, the deck was completely clean.


  • Easy process
  • "Eco friendly" product.  No bleach.  No harsh chemicals. Safe for plants and animals.
  • Works!
  • Protects?- The manufacturer suggest that doing the cleaning on a regular basis will help prevent mold from coming back and make it easier to remove it if it does


  • Didn't mix well.  The crystals barely seem water soluble
  • Took a long time to rinse- but, the manufacturer says any left on the deck surface will continue to clean until it is thoroughly rinse off.  So, not so bad as long as you don't leave too much on there.
  • Expensive?  I didn't compare the price to other deck cleaners, but at $30 a bag for a bag that does the average size deck, it seemed a little on the high side to me.  Of course, it is far less expensive and far easier than staining or painting the deck.  I think when I try it again, I'll dilute it more than they suggested because it seems the concentration was pretty high anyway.  It was difficult to mix and difficult to rinse.  A lower concentration should be easier to work with.
Overall, I was very pleased with the product and would recommend it.  Now that I know how easy it is to do, I won't wait three years to clean the deck again.