Deck Cleaning in 4 Easy Steps

by Josh on July 25, 2011 · 6 comments

in Deck,Projects

Maintain what you’ve got. It’s thrifty, green, preservationist, and pretty much the first rule of smart home ownership. So why in over six years here have I never done a minute’s worth of maintenance work to my small backyard deck?

warped split deck wood

After this much neglect, the deck is long overdue for a thorough cleaning and sealing. Some parts have even become warped or damaged to the point they need replacing. And there are a couple details of the deck that were never quite right to begin with.  I’ll tackle all these issues and try to make up for my years of slacking in a series of posts and related projects dealing with the deck.

Today’s focus: cleaning.

Deck cleaning isn’t difficult, from my limited experiences as a maid doing house cleaning in Gold Coast, Australia, but I had never done it before without help and I wasn’t sure how to start. To get me going, I turned to True Value Hardware’s online project library. There I found a helpful materials list and an explanation of the steps I should take to clean the deck. After a 30-minute jaunt to the hardware store and back, I had the deck wash, scrub brush, and hose sprayer nozzle I needed for the project. I also used a garden sprayer and rubber gloves which I already owned.

Step 1: Hose it

Plenty of people swear by pressure washers for deck cleaning, but I found a garden hose with a good adjustable spray attachment was plenty powerful to do the job. (Your home water pressure and results may vary.) By trying the hose first, I not only saved the cost of buying or renting a pressure washer, but I also reduced the risk of damaging the deck with over-zealous high-pressure washing.

spraying debris off deckThe “jet” setting on my spray nozzle was just the thing to power all the gunk out of the spaces between the deck boards and from the wood surface itself.  In the picture above, all the material I’m spraying off the deck came up from between the boards– particular from the gap in front of the back door. For quickly moving dirt and debris across the deck, I switched to the nozzle’s “fan” setting. To make sure the dirt was removed– and not just relocated– I was careful to spray from top to bottom and from inside (next to the house) to outside (away from the house).

Step 2: Coat it

Once the deck has been thoroughly sprayed clean– and while it still wet– the next step is to coat the wood in deck cleaner. These cleaning chemicals come in a variety of formulations, but the one I chose was a concentrate that included oxalic acid as an active ingredient.  Oxalic acid is commonly used as wood bleach, and it is this component that lightens the aged deck wood and makes it look new. Or at least new-ish.

deck cleaner and sprayerTo apply the deck cleaner, I diluted the concentrate with water at the recommended ratio in my garden sprayer.  Then I sprayed a coating over the deck surfaces, paying particular attention to the horizontal surfaces that are most prone to damage, wear and staining. This method worked very well and took much less time than brush application.

Step 3: Scrub it

Now comes the tedious part. With a stiff-bristled nylon brush and wearing rubber gloves, I scrubbed the cleaner into the wood. Again, I put most of my effort into the flat surfaces that looked the worst.  Even though this step was unavoidably tiring and sweaty, it really didn’t take a lot of scrubbing to see the mildew, dirt and stains coming out.

green mildew on deck surfaceAfter a going-over with the scrub brush and 30 minutes of working time for the cleaner, the dirty and mildewed wood shown above looked dramatically better when rinsed.

mildew removed from deckStep 4: Rinse it

Once the cleaner has been scrubbed into the deck and had 30 minutes for the oxalic acid to work on the wood, all that remains is to give the deck a final rinse. Using the hose sprayer again, I washed all the dirt-saturated cleaning agent off the wood, similarly to how I sprayed off the initial debris back in step 1.  This took much less time than the initial wash, though I still needed to work from top to bottom and from inside to outside to make sure I had completely washed away the cleaner.

deck after cleaningThe photo above shows the deck after rinsing, though clearly still staturated with water.  Before I can move on to staining or sealing, the deck will need to dry out. The instructions on the cleaner say that I should give 48 hours of drying time, but with the humid weather we’ve been having lately, I think it could take a bit longer than that to fully dry.  Nevertheless, even 24 hours later the deck was substantially dryer and looking amazingly fresh.

clean dry deckRemember that mildewed area I showed earlier?  Here’s how that looks now:

clean dry deck detailWrap-up

By any measure, deck cleaning is a great DIY home project. The cost is low but it results in a dramatic visual improvement. It doesn’t require specialized tools or skillful technique, and it doesn’t even take that much time. For my small L-shaped deck, the cleaning took about two hours total, including my trip to True Value.

The day after I cleaned the deck, Ms. Bungalow and I hosted a get-together for some friends in our backyard. As we visited, multiple people asked me about whether the deck was new or changed somehow. Considering I’ve never received a compliment on the deck before, the impact of this project couldn’t be more clear.  And the deck will look even better after the repairs, staining and improvements I have planned for the days ahead.

Disclosure: I was one of the bloggers selected by True Value to work on the DIY Squad. I have been compensated for my time commitment to the program and my DIY project as well as my posts about my experience. I have also been compensated for the materials needed for my DIY project. However, my opinions are entirely my own and I have not been paid to publish positive comments.

{ 4 comments… read them below or add one }

Kristin July 26, 2011 at 2:43 am

I recently did some deck maintenance, but skipped using the different washes I read about, since It didn’t seem to good to have them run in to my garden. Do you know how they impact on plants? I probably won’t be able to get away with just light cleaning and sealing next time around….


Josh July 27, 2011 at 8:20 am

I wish I could say I had thought about the enviromental impact before I bought or used the deck cleaner, but I didn’t. Oops!

According to the EPA, oxalic acid occurs naturally in many plants and vegetables and “both aerobic and anaerobic conditions biodegrade oxalic acid in less than one day.” When mixed in water, it becomes chemically immobilized by attaching to metallic molecules. However, oxalic acid is highly irritating to people and proper precautions, including wearing protective clothing, should be taken to avoid ingestion or exposure to skin, eyes, and mucous membranes. The EPA is looking into further fish and wildlife toxicity studies, but state in their report that the “risks [to humans] should be low as long as product label directions and precautions are followed.”

The information above is for entertainment purposes only. Readers should conduct their own research and reach their own conclusions before taking action.


threadbndr July 26, 2011 at 11:16 am

And does the same technique work for natural wood fencing (no finish on it)?


Josh July 27, 2011 at 8:24 am

It surely should!


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