cleaning composite trex decks

15 years ago

I have a trex deck with black marks like leopard marks on most of the boards. Looks like it might be mould. The deck is in the bright sun for most of the day and not all the boards have these marks on them. One long board is absolutely perfectly grey but the boards on either side are pocked marked. Tried a deck cleaner from home depot and it helped but the marks are still there. Anyone had a similar problem?

Comments (33)

  • johnplace
    15 years ago

    Trex is notorious for growing mold. The stuff is half wood dust and half plastic -- the wood portion tends to attract mold. It also tends to rot (especially on the older Trex that was part of the class action). Since the plastic does not rot, the result is pock marks.

    I am not knowledgeable enough to recommend a cleaner, but I'm sure someone else here is. Or you could always call Trex -- I am 100% certain they've heard this complaint before.

  • livvysmom
    15 years ago

    We have the same exact problem with our 1 year old deck. I believe the manufacturer recommends cleaning once a year (some sort of cleaner and a push broom I think). Hope to hear from others on how they cleaned it.

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  • pressurepros
    15 years ago

    In a 3 gallon pump up sprayer:

    2 gallons of Clorox Outdoor Bleach (Home Depot)
    1 gallon warm water

    Apply, brush vigourously, let dwell for ten miutes, rinse with hose

  • deckman22
    15 years ago

    Pressure pros nailed it.

    I have a customer that I put down trex's newer "saddle" color about 4 years ago & he has the same problem. He told me he uses a 50/50 mix of bleach & hot water along with a stiff broom once a year.


  • lgraphics
    15 years ago

    Factory direct pressure washers, parts, detergents and accessories. We carry a full line of residential and commercial washers and parts for most models.888-649-6449,, e-mail -

  • ryan_home
    14 years ago

    I have used a new composite deck cleaner called Corte-Clean ( now being recommended by Trex for all of my cleaning issues. It works far better than anything else. It kept the mold away far longer than chlorine bleach or oxlaic acid based products and cleaned the deck far better than anything else. It is also environmentally friendly and less money. I highly recommend it!

  • cat997437
    14 years ago


    I have used Corte Clean Environmentally Friendly Composite Deck Cleaner on my Trex wood plastic deck. It worked extremely well with little effort. It removed most common house hold staining issues including ground in dirt, mold, mildew, grease, barbecue stains, etc. It worked far better than Olympic Deck Wash, BEHR No. 62 Multi Surface Cleaner and Mildew Stain Remover or any number of the other products I purchased and tested.

    When it came to removing the black mold and mildew spots Corte Clean worked far better and for less money than the PSC Composite Deck Restorer with out the harsh chemical smell or potential dangers of chlorine bleach. Corte Clean did not corrode my fasteners or kill my plants like the chlorine bleach based products.

    I noticed that after using the chlorine bleach based products that contain sodium hypochlorite (active ingredient) to remove the mold, the mold never was completely removed. I noticed black spots only when the deck was still wet. Any way, the mold grew right back. In fact, all I was doing was removing the dead surface layer of the mold and was watering the mold roots. See the links on the Corte Clean web site to OSHA, the EPA and Spore-Tech before using chlorine bleach on a POROUS surface like Trex composite decking.

    Chlorine Bleach (sodium hypochlorite) like Clorox and Clorox Outdoor work best on NON-POROUS surfaces like ceramic sinks and showers for killing germs as confirmed by the Occupational Safety & Health Administration (OSHA).

    I bought my Trex deck because of its environmentally friendly reputation. I can not understand why they do not have this eco friendly composite deck cleaner that is specifically designed for composites on their web site even though they have tested it and know it works. I highly recommend Corte-Clean Trex Deck Cleaner. Nothing works better.

  • larry324567
    14 years ago

    Chlorine Bleach or Sodium Hypochlorite (active ingredient in Chlorine Bleach) based deck cleaners that the uneducated recommend may appear to quickly remove mildew (white in color) and mold (black and other colors) fungus from Trex and other Composite Decking. Nothing could be farther from the truth.

    The Environmental Protection Agency (EPA) and the Occupational Safety & Health Administration (OSHA) DO NOT RECOMMEND Chlorine Bleach for Mold (Mildew is a species of Mold) remediation on porous surfaces such as Trex and other composite decking.

    The reason for this is that Chlorine Bleach does not remove or kill the roots (mycelium) of the fungus, but actually waters them. A few weeks after you have cleaned a deck with chlorine bleach or sodium hypochlorite based products you will notice the mildew or other mold fungus growing back in greater numbers, especially after additional moisture comes into contact with the deck. It will make the problem worse and harder to remove the next time the composite surface becomes unsightly.

    In addition, Chlorine Bleach products reek havoc on the rest of the deck structure shortening the life of the entire structure. It is highly corrosive to any metal including structural connectors or fasteners (screws) holding the deck together. It shortens the life of the pressure treated lumber supporting the deck. This could lead to liability issues for the owner of the property and any company who recommends its use.

    PRODUCTS THAT CONTAIN SODIUM HYPOCHLORITE ARE ENVIRONMENTALLY DESTRUCTIVE. It is shocking that Trex and other composite manufacturers do not follow the recommendations of the EPA or OSHA and recommend one of the most TOXIC chemicals known to this earth but sell their products as ECO FRIENDLY.

  • john_hyatt
    13 years ago

    JK, Man its a bad deal with trex or t-junk,they are defentley the low life of the Business, Dammmmm 20 grand thats a mojor chunk of change.

    If the Contractor installed the material corectley he is outa there dont matter if he recomend it or not.

    You might get some $ out of the t-junk boys but it will take a while although they set in motion $45 million to pay for defective material made in Navada last I heard it was up to $ 68 mill so Mabey you will get something after a major effort on your part.

    Its not your fault being ignorant can be fixed the scam t-junk has pulled all these years goes clear to the bone.

    It is possible to put a finish on the soft composites like trex,probley wait until any cash comes your way but that kind of money invested I cant see them doing anything that will help you in the short term.
    Sorry Man, J.

  • jerryd_2008
    13 years ago

    Earlier this year, I got nowhere with Trex. They gave me a 25% off coupon for some extremely expensive deck cleaner called Expert Chemical Composite Deck Cleaner and Enhancer only available by mail. Their web site describes 3 passes over the deck with the cleaner and the use of a brush to scrub. This process results in only 100 square feet coverage per gallon that cost like $17/gallon.

    I was NOT happy since I already used their recommended cleaner, Behr Multi Surface Cleaner, that did NO good. It did however cost only a fraction of the above cleaner.

    We are in Northwest Arkansas and the deck has an extreme southern exposure. This environment seems quite different than what I would expect in Seattle. We are still having difficulty accepting that this is mold or mildew since the temperatures get quite hot for a number of months every year. My wife even thinks that the spotting is worse in the direct sunlight.

    Would somebody please explain to me where the Corte Clean Environmentally Friendly Composite Deck Cleaner at came from. I see no such product mentioned in my Trex MOLD TECHNICAL BULLETIN.

    Jerry D

  • walt54321
    11 years ago

    I installed a trex deck last year and had the black spots appear within a couple of months. So I went out and bought the corte clean that trex recommends but decided to do a precleaning with some Simple Green Heavy Duty I had laying around. Even with a very diluted mixture the deck came out like new with light scrubing. I will be returning the expensive Corte Clean because I dont believe that it could get much cleaner. Just an FYI though, my deck is less than a year old so Im not sure how well this stuff will work on a deck that has gone longer without cleaning. Just thought Id share my experience with all the other frustrated owners of trex out there.

  • fightplutocracy_yahoo_com
    11 years ago

    I hate to be a naysayer, but I have found nothing that satisfactorily removes mildew stains from Trex (and I've tried four different commercial cleaning products). Corte-Clean's main ingredient is Trisodium Phosphate (TSP)--look up the ingredients--at a tremendous mark-up. Moreover, it is a product that cries out for more specific warnings. IÂm not sure how they can describe it as "environmentally safe" since, like TSP, it seems to have relatively high levels of phosphate and at a relatively heavy concentration it is extremely caustic to the skin. (Whatever you do, do NOT mix it with bleach; in an attempt to figure out itÂs chemical properties, I mixed a very small amount of bleach with a small amount of Corte-Clean. The ensuing chemical reaction began boiling and threw the solution up in the air several inches; fortunately I had on rubber gloves).

    It is true that bleach based solutions pose a difficulty; they can affect the structural integrity of your fasteners, particularly if they are galvanized rather than stainless steel and in high concentrations they can discolor your decking. But the only solution to the problem of deck mildew IÂve found is to clean the deck well with a scrub brush and a dilute mixture of TSP (1/4 cup per gallon) or even a non-phosphate detergent. After it is rinsed and dried, I wait for a sunny hot day and then use a garden sprayer to cover (but not saturate) the deck surface with a dilute solution of bleach (I use 1/4 cup per gallon). I let it dry and sometimes have to repeat; then I rinse thoroughly. Is this ideal? Is it as sound ecologically as I would like? Absolutely not. (It also takes patience, care and a lot of elbow grease). All I can say is that I have not found any commercial solution that will remove mildew from Trex in my Southern highlands/high humidity climate. None. And believe, me, I've tried them all.

    Frankly, IÂve concluded Trex, like other plastic/wood based synthetic decking is not a good product in Southern/high humidity climates. The best alternative, though pricey, is IPE, but I do not recommend it because of environmental issues. (ItÂs a very slow growing tropical hardwood that is essential for the ecosystem where it thrives and it is being illegally logged because of, admittedly, its outstanding properties.)

    No.1 treated Southern pine is sustainable and, if allowed to dry properly and then carefully maintained with a good quality solid or semi-solid water based stain, will last 20 years. Ideal? Does it look like a spread in a house magazine? No, but you can install it with a relatively clear conscience. And I still havenÂt found a responsible alternative.

  • john_hyatt
    11 years ago

    I put down a lot of Ipe, as well as Garapa and Masenranduba.

    I have a completley clear conscience,if fact its really clear, in fact I love doing it. I feel so responsible I put on a green badge every day.

    Using South American lumber is environmentaly the Best Choice for outdoor projects for a lot of reasons.

    SYP preasure treated will not last 20 years exposed to the weather no matter how it is finish or fastened....reread....again....again...past it to your forhead. John Hyatt

  • pat_m
    11 years ago

    Hello, I am a representative of Trex. Spotting is usually a sign of mildew that originates from pollen, dirt, grass, etc. To resolve your concern we recommend the following:

    Clean the entire deck with a deck wash containing detergent and sodium hypochlorite, commonly known as bleach. This deck wash will lighten the wood on the surface of Trex in addition to removing the mold. To minimize lightening of darker Trex colors,dilute deck wash with 50% water.

    TIP: Cleaners work best when decking is completely dry.

    The following brands of deck cleaners have been found to be effective in removing mold from Trex decking:
    - Olympic Deck Wash
    - Expert Chemical Composite Deck Cleaner & Enhancer (

    ***Follow all package directions for usage, safety and disposal. NEVER mix any other cleaners ammonia, phosphoric acid, etc.) with bleach.

    - Non-chlorine based alternative UltraMean can be used but will require scrubbing
    with a soft brush immediately after application. (

    - Eco-friendly (no bleach): Corte-Clean Composite Deck Cleaner (

    Mold spreads easily and may return in some environments despite proper cleaning and preventative measures. Mold does not damage Trex and will cause no structured harm if allowed to propagate. In some cases it will require several treatments with the deck wash to completely remove all mold colonies. Even if the spots are no longer visible,there may still be mold spores on the surface that could regrow.

  • peg10_deck
    11 years ago

    We had a Trex deck built in Oct. 2006 and it's horrible. I have same problems everyone else seems to have with the spotting. I cleaned it with a bleach solution a couple of years ago and it only slightly lightened the "saddle" color and did nothing to the spots. I had it power washed last year for $200 and it didn't even touch the spots. I would NEVER recommend Trex to anyone. It's horrible. We have a large deck off our kitchen/family room and a smaller one off our study upstairs. I'd love to get rid of them and build new ones but we spent almost $10,000 for them. They're sturdy but very ugly. The house was originally built with a Redwood deck that was rotting through the posts so it was dangerous. I was looking for a "maintenance free" deck. HA Talk about false advertising. I also got the recommendation to clean it with Olympic or the other mail-order cleaner. Not too anxious to use either produce with the reports posted here. Has anyone stained or painted Trex? Was wondering if a Kilz coat would cover the spots and then it could be painted or stained.

    Thanks for the Posting and for letting me vent.

    all one off our study

  • john_hyatt
    11 years ago

    Sorry for the mess Peg. You have just joined a very large Club of Livid t=Junk members.

    But your stuck with it. One thing soft composite like t-junk takes outdoor finish real well, just sucks it up, if you used an oxalic acid wash, a lot of scrubing,two coats of high grade outdoor finish like TWP or Woodrich it will give your deck a fighting chance.
    Hang in there J.

  • brittanym
    11 years ago

    I am providing you with a few suggestions for paint manufactures you could use:

    Sherwin Williams: 1-800-474-3794 or 800-4SHERWI. You can request a copy of their two page written specification sheet. Sherwin Williams recommends their DeckScapes Exterior Acrylic Solid Color Deck Stain line on Trex decking.
    Behr Deck Plus Solid Deck Stain: 1-800-854-0133
    If you wish to use another brand, please contact their technical support department for their recommendations.
    Please let me know if you need any further assistance.

  • brucemarko13_comcast_net
    10 years ago

    Wow...that's a lot of unhappy Trex customers...I live in the North Metro Atlanta area & looking to purchase a few 20', 16', and about 20 12' long saddle Trek boards. In case any of the unhappy customers would like to get rid of their Trek, I'd be happy to pick up & pay a fair price. If not, if anyone knows where I can purcahse at a discount, please let me know. Thanks.

  • fized1_yahoo_com
    10 years ago

    Don't buy this crap, even if it's used. It's frustrating to pay $8000 on a deck and then a year later have it look like a leopard. I'm trying Wet and Forget today. We'll see how that does. Should be called "TREX FORGET". DON'T BUY TREX!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  • delsol40_gmail_com
    10 years ago

    I live in the Northwest so mold is a problem, oxyclean and vinegar and really hot water and alot of elbow grease 3 times a year helps keep the mold and dirt back, i have had mine for 5 years, im pretty happy.

  • ches330_frontier_com
    10 years ago

    Thanks Carrie. I did the oxyclean and vinegar with hot water it works well especially when accompanied by a stiff brush and power water. I didn't want to use bleach because I was concerned about the plants around the deck and the harshness of the beach. For the most part we are very happy with our deck -- it is much better than the wood deck we used to have.

  • stoppickering_yahoo_com
    10 years ago

    What can be added to this? Nothing except to reaffirm that Trex is simply not suited for any area with a combination of high temperatures and moderate to high humidity levels. Although I have a lot of experience in construction and renovation, I am embarrassed to say that I let a deck contractor persuade me to use Trex five years ago. I think I can truthfully say that it is the worst building product I have encountered in over 40 years in the business. Not only did it mold immediately, but--even though it was installed with the correct gap--during the cool rainy season, the boards swell to the point that they close the opening between the boards during the winter so that there is no way for the water to escape to the ground below and any slightly low place becomes a permanent puddle.

    As for cleaning? Forget it. Sure, various products--tsp/bleach/commercial cleaners--will beat the mold back, but it returns with a vengeance. There are other synthetic products on the market that are less susceptible to discoloration and mold--check them out. As for me--after getting a complete runaround from Trex (my contractor had headed off to fields unknown and the building supplier had gone bankrupt)--my plan this fall is to rip the damn stuff up and start over.

    What a bunch of shysters; the people who manufacture Trex make used car salesmen look like Mother Theresa.

  • furnone
    10 years ago

    I have a Portico composite deck, similar to Trex, although a comparison in 2005, when I installed it, led me to believe that it's superior to Trex.

    Anyway, it has the same problem with "leopard spots". I thought is was from tree sap. I tried several methods and products and did a lot of scrubbing until I tried Olympic Premium (apparently, different than plain) Deck Cleaner.

    I spray a wet coat on a perfectly dry (it doesn't work if the planks are wet) deck, wait around 5 minutes, give it a light brushing with a soft bristle brush, and rinse it off with a 1600 psi pressure washer. I think rinsing with just a hose would do it.

    I have been doing this since the 2nd year and it looks like new until the next winter.

    It's $15.43 for a 2 1/2 gal. container at Lowe's. Home Depot, 1/2 mi. from my house, doesn't carry it so, I have to drive 10 miles to Lowe's for it.

  • mokalabs_gmail_com
    10 years ago

    I just tried OLYMPIC PREMIUM DECK CLEANER also (says its "excellent for composite and cement" and it worked wonderfully. Remember it needs to be APPLIED TO A DRY SURFACE and you can see the results immediately. I bought a short bristled long handled brush to apply it to the deck (light scrubbing to tough areas. I agree the larger container 2.5 gallons was better ($10 for one gallon). It was instantaneous.

  • hardworkingwoman
    7 years ago

    I am cleaning my trex composit deck with spray on foaming bathroom cleaner - kills mold and mildew, so I tried it and it works amazing. The foam stays in place for a couple of minutes, its cheap and just a quick scrubbing pulls the mold off. I am using Kaboom with oxi clean - foam bathroom cleaner that comes in a can. Good luck!

  • jross6
    7 years ago

    I live in the suburbs of NYC. I have trex decking, around my pool, two decks, upper and lower, three sets of trex stairs, and along the whole side of my house up to the front, pretty extensive. I had it installed 10 years ago. I used two different colors, the brown with lighter tan treads, spindles, railings etc, it's very nice looking. It gets some mold on it, in some spots, not everywhere, and some stains from the bbq, and food droppings, etc, BUT, I would rather clean my deck every year, or more often if I need to, and be done with it, even with some some stubborn stains remaining and the fading of the color, than have this much wood decking that would require so much more attention and other worries, any day. I like the fact that it gets cleaned and disinfected every year. My husband once upon a time, installed wood decking, and refinished wood decks, etc etc, and he would NEVER put this much wood deck around our house. The composite is soft and feels good on your feet, without the worry of splinters, and thats a big deal for me with children. It does get hot like sand sometimes, in the summer sun, so we keep a hose near the pool to cool off the deck, and it looks nice wet anyway. It has it's issues, but they are not even noticeable in the big picture. They are coming out with new cleaners, and now you can paint and stain it if you want. The benefits of trex, when installed properly, far outweigh the inevitable, over time, every year, and every day, issues you will have with a wood deck. We paid a lot of money to avoid the problems you have with wood decks because of my husbands experience and knowledge of wood decks, and I hope this doesn't jinx us (knock on wood) but, we are very happy with ours, we would do it again in a second. Just my opinion....:)

  • triplitt1
    6 years ago

    Hi: We have white spots remaining from pitch removed from a dark colored Trex deck. Can you PLEASE advise on what will remove the white spots without damaging the Trex. Thank you very much!

  • Rich W
    5 years ago

    Bleach is horrible for composite decks (and the environment). I am a chemist and work with composite decks. The previous posts about it and oxalic acid are accurate. You will create a worse problem than you had and possibly ruin your expensive deck. Look for a non bleach cleaner. There are also treatments to help protect the deck from mold and other stains (dont use a coating/paint or you will be in for a lot of work every couple years). We love a product called resist mist for composite decks ( Works for several years and recommended by some big deck manufacturers. They have a cleaner and a treatment.

  • PRO
    Rhino Hide Llc
    5 years ago
    last modified: 5 years ago

    Hi, everyone!

    Rhino Hide ( ) here to answer a few composite deck questions you may have. Unfortunately, we do come across this issue with composite decking quite frequently. Depending on your climate, mold staining can be problematic and really hard to get rid of, especially if the wrong chemicals are used to clean it. Several commenters were spot on when suggesting that chlorine bleach should never be used to clean the decking. Not only does this product degrade the quality of the deck but almost always makes the staining much worse. Here are a few helpful articles we have put together for anyone wondering what to use and where to start... Hope this helps!

  • triplitt1
    5 years ago

    We have dark colored Trex with white pitch spots all over it. Have tried a number of things to no avail. PLEASE, PLEASE suggest something that will work! We love that it doesn't splinter or require a lot of upkeep, and just want it to look nice! Thank you!

  • Rob Hailes
    4 years ago

    According to the MSDS for Corte Clean, the main ingredients are sodium per carbonate and sodium metasilicate. These ingredients are found in Oxi-Clean and Phosphate-Free TSP respectively. You could make DIY Oxi-Clean by combining 1/2 cup A&H Washing Soda and 1/2 cup Hydogen Peroxide in 1 cup hot water. Make a 2 gallon solution of sodium metasilicate by mixing in 1/2 cup of PF-TSP. Add the DIY "Oxi-Clean" solution to the 2 gallon PF-TSP solution. It will remain active for only @ 6 hours so make it as you need it.

    You just made a version of Corte-Clean for A fraction of the cost.

  • HU-880260095
    2 years ago
    last modified: 2 years ago

    We live in a high temperature AND high humidity area and the Trex has been great. It's really kept its quality over time and we use a product called Spray and Clean by Wash Safe, which I'll include a link below. They sell it by the gallon but our deck in the back is smalller size so we just buy the hose end bottle every spring. Has anyone else tried? Aside from cleaning in the spring/summer, I want to know what I can do in the Winter and if salting my steps will be bad for it. I haven't used the deck stairs in past winters and this will be the first time we use the back entry to go down so it will require lots of salting. If anyone has any tips - please let me know.