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Deck Cleaning Questions and Answers
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Topic starter
14/09/2020 5:19 pm
I recently installed a very large garapa deck in our backyard. We wanted to keep the natural look of the wood so when the lumber arrived we sanded and used a gloss and satin finish on both sides of the wood. The deck picks up a lot of moisture in the mornings its pretty wet all over and about a month ago I noticed some black spotting on some of the wood. The spotting has appeared on about 30-40% of the deck and from everything I read online it appears to be mold. There doesn't seem to be a rhyme or reason to which boards have it and which boards don't although the lighter boards seem to not have as much of it as the darker ones. I'm obviously frustrated about spending a lot of time and money on the deck and having something like this where it appears I'll have to refinish it. I'm hoping someone can help and answer the following:
1. Is the mold something inside the wood that will keep coming back if I strip, brighten, and re-seal?
2. What are the best products for removing the mold? I've spot-tested the EFC-38 from Woodrich on a couple of places and while it lightened the wood and minimized some of the appearance of the black spots it didn't take them away (see attached photo)
3. Will the mold spread to the entire deck if its left untreated?
4. Can you recommend any sealers that are clear and contain a fungicide?
Thanks for your help. I've attached a couple of photos.
14/09/2020 5:28 pm
You cannot use a gloss sealer on a wood deck. It will peel, blister, and attract mildew. You will need to remove it fully. Most likely by sanding. Once sanded down, clean and brighten all wood with the Restore A Deck Kits.
Clear sealers will not provide UV protection from graying. You must have a tinted stain for UV protection. Your best option for this and the mildew is to use a penetrating water-based stain that is semi-transparent. Try Restore A Deck Stains or Defy Hardwood Stains.
Topic starter
14/09/2020 6:08 pm
Thank you...the gloss sealer was recommended by the company we purchased the lumber from. Do you think the mildew is attributable to the sealer? If so, I'm confused as to why it would only be on about 30-40% of the deck when it was all treated the same way?
Topic starter
16/09/2020 1:56 am
Ok so in terms of addressing the issue do you think it can by be solved with just sanding and applying a stain with a fungicide? I purchased a sodium bicarbonate solution and wood brightening kit (EFC38 and Citralic) but I’m not sure which order to complete this in. The sanding seemed to take it all away, then i applied the cleaner and brightener but the final tone of the wood looked a little off and i sanded it again which made it look great. The deck is large and I’m trying to avoid having to sand it twice would you recommend doing the cleaning and brightening them sanding or do i even need to do the cleaning and brightening if I’m sanding and using something with a fungicide? Thanks for your help!
