Having tried biodegradable dish soap to wash my deck, I'll never go back to commercial deck cleaners!
How to Clean Unfinished Wood and Restore That Natural Smell
If your beautiful, unfinished cedar or other natural wood deck is looking more weathered than you would like or has moss, lichen, or other dirt on it, there's a quick and easy way to clean it without wasting money on harsh chemicals. I've done this many times on my own bare cedar deck, and I get better—and faster—results than when I used commercial deck cleaners. Note that this process may or may not work on decks that have been painted, stained, or varnished—test in a small hidden spot before attempting to use this method on the entire surface.
It is easy to do and won't spoil your entire weekend like painting/staining will.
Just soak, quickly scrub with a deck brush, and rinse. Works great!
Supplies You Will Need
- Deck-scrubbing brush: A stiff-bristled brush on a stick so you don't have to bend down or work on your hands and knees. A stiff-bristled broom may also work.
- Dawn liquid dishwashing soap*: With oxy and enzymes—it's biodegradable and safe for kids, animals, and nearby plants.
- Large bucket or container: With a volume of about 5 gallons.
- Optional: A smaller brush or two to get into corners and crevices.
*Other brands of dishwashing soap may work just as well, but I can't recommend them because I haven't personally tried them.
Important: Never Pressure-Wash Bare Wood
Resist the temptation to use a pressure washer on real wood decking or siding!
Pressure-washing may appear to solve the immediate problem(s), but it raises the grain of the wood on the outside, thereby damaging the wood. This makes the wood more susceptible to rotting and insects, increases the likelihood of getting splinters, and makes it difficult to stain uniformly if that is what you plan to do.
If you inherited a real-wood deck that was pressure-washed by the previous owners, I recommend sanding a very thin layer off the surface of the wood. This will bring back the new-cedar smell (especially on damp, early mornings or rainy days) and solve most of the problems caused by pressure-washing the wood.
Apply Soapy Water to Your Deck
- Pour a medium amount of Dawn® dishwashing liquid into your bucket—about twice the amount you'd use to wash a sink full of dishes. You want to get a lot of soap suds in the bucket (about half water, half suds)!
- Fill the bucket with enough water to cover your deck surface or as much as it will hold without spilling the soap suds floating on top.
- Using the deck brush, apply the soapy water liberally to all surfaces you want to clean. If your deck is very large or if you have a lot to clean, you may need to make another batch of soapy water.
- Wait 10-15 minutes for the soap to soak in and do its work. Make sure the surfaces don't dry out during this time. Use a hose to apply a VERY light mist of water to any drying areas. Apply more soapy water to any areas that start to dry too soon. An overcast day is best for this job.
While You Wait for the Soapy Water to Work Its Magic
This is a great time to get a scrub brush out and a big sponge and get the whole family together to wash off the deck furniture and cushions, decorations, flower pots and baskets (wash these down on the ground—not on the deck—to keep the deck from getting dirtier), and anything else you've got out on your deck. Even very little kids can help scrub flower pots and boxes. Use the same method described above.
Trivia: It's good to have children do chores around the house. They will grow up to be better adults if they do!
After 10-15 Minutes of Soaking, Scrub/Brush Away the Dirt
- Use the deck brush to brush or scrub the grime right off of your deck—even the dirtiest, darkest messes should come right off with minimal scrubbing, leaving beautiful, natural wood underneath.
- When you are done scrubbing, either hose off the deck or empty your scrub bucket on a particularly dirty section and then hose off the deck using a mild to moderate water pressure. DO NOT use high water pressure!
- If there are any remaining areas that are dirty, you may need to repeat this procedure again and do more scrubbing to get it clean. If all else fails, you can try a small amount of Formula 409 or an alternative, green cleanser.
- If any dirty areas remain, repeat this process.
- Warm water may work better, although, I use the cold water straight from the hose with excellent results.
- This process probably works just as well with other outdoor items, like plastic faux-wood decking, and wood or plastic outdoor furniture. Test in an inconspicuous spot before attempting to clean entire objects.
- I do not recommend pressure-washing real wood decks—bare or stained—because it causes the surface to become damaged. You can feel the difference by walking barefoot on it before and after. The damage pressure washers do has been in the news a lot the last few years despite the fact that they are still sold for this purpose. Destroying the wood surface by using a pressure washer is probably going to reduce the wood's lifespan, increase its vulnerability to insects, change how it works with stains and clear-coats—if you plan on using them—among other things. The cleaning method I describe above works on bare wood with mild to medium hose pressure or a mop and clear water. It won't damage the deck surface—all you need to do is gently rinse off the soapy water and grime.
If this process works just as well for you, or on other outdoor objects, or if you have an even cleaner/greener/easier solution, please let me know!
Dish Soap Works for Cleaning Siding and Roofs, Too
This method works tolerably well at removing dark spots, dirt, pollution, mold, and lichen from wood house siding and roofs. It also works on some other kinds of siding such as aluminum and steel.
Caution: Be sure to experiment in a small, hidden area before using this procedure on your whole house! You don't want to have to re-paint or re-side your whole house if this doesn't work for some reason!
To clean a small section of siding, use a bucket of sudsy water as described above.
To clean all of the siding, use a clean, preferably new—and mark that it is dedicated for this task—plastic suction-based pump that attaches to the end of your hose and is designed to dispense liquid fertilizer (or, in this case, concentrated sudsy water) into the water stream.
I can't advise you on how much soap or soapy water to put into the uptake container or what setting to set the hose at—every situation is different and there are numerous models of dispensers on the market. So, a little experimentation will be necessary.
Again, DO NOT pressure wash real wood (even if it's painted), and don't forget to wait at least 10 minutes to let the soap soak in and do its work. Then, use clear water to thoroughly rinse away all of the soap.
Tip: Most of these suction pumps have a "clear water only" setting, so you don't even have to reconfigure your hose to switch between these two tasks—or to mist sections that appear to be drying. Again, a cloudy day is best for this task. Work in sections so that you can make sure no soapy water dries on the siding.
Important: Even if you have a walkable roof, I recommend hiring roofing contractors to clean your roof. Roofs are always dangerous for a number of reasons—best to leave this to the pros unless you can reach the problem areas without needing a ladder.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2009 Laura Schneider
Jean Holland on September 02, 2020:
we have a cedar deck not sealed and it looks terrible with stains and can I use simple green to clean it? Want it to weather natural to
gray but looks dirty. Please advise.