How to Clean Hardie Siding

(Updated January, 2021)
James Hardie products are some of the best materials on the market, both for looks and durability. But one thing they won’t do is clean themselves. With the wet Pacific Northwest weather, the siding on your home can start to look a little grimy. When the sun does come out, the mess can get baked on.

Loose mud, dust, or dirt after heavy rains can be hosed off if you get to it soon enough. But if you wait a few seasons, your James Hardie board siding can start to look a bit messy. This is especially true after removing bushes and other vegetation that hid or even helped mold and mildew to grow.

A note using power washers to clean your siding: We don’t recommend it. A power washer is perfect for sidewalks, driveways, and other concrete surfaces, but if used incorrectly on home siding, could be damaging. Not to mention the possibility of removing paint that is in otherwise good condition.

How to Clean James Hardie Siding

At Joseph Ketner Construction, we’re staffed by experts at siding installation, siding replacements, and exterior renovations and design. We can certainly advise you as to what we think is the best house siding cleaner. However, we leave the long-term cleaning to the homeowner.

There is some good news, though. Many of today’s finest siding materials don’t require all that much cleaning — or overall maintenance for that matter. Still, to keep up appearances, we recommend assessing your siding and cleaning every 6 to 12 months if needed.

With regular cleaning, you can extend the lifespan of your home’s exterior. In most cases, the cleaning method only requires you to rinse the area, grab a soft sponge, and wipe in a side-to-side motion. Work from top to bottom so the dirty water runs down the siding you haven’t cleaned yet.

Mildew stains take a little more work. But you don’t need a pressure washer or a gallon of water mixed with a cleaning solution. The nasty green stuff will require a little extra work on your part, however. You’ll need a cleaner that’s specifically designed for mildew (look for all-natural cleaners and avoid harsh chemicals when possible).

Cleaning Products

There are a lot of house siding cleaner products out there on the market. These items advertise themselves as “specially formulated” and “the best.” But how many products say they’re “specially formulated?” (Answer: a lot.) And how can we determine the best?

In reality, a house siding cleaner is only as effective as the methods and the tools used to do the actual cleaning. For example, wind-blown dirt and dust can be easily cleaned off with a garden hose, a soft cloth, and a soft brush. No “specially formulated” cleaners are necessary.

Just be sure the brush is, in fact, soft (non-metal); anything other than a soft bristle brush may damage the siding or the finish. Remember to wear protective gear while cleaning: eyewear and gloves are a must. People with even mild respiratory problems should also consider wearing a mask.

Oil, Grease, Grime and Mold, Moss, Algae

The job gets a little harder if your siding has been dirtied by oil, grease, or similar grime. You’ll still need water — but you’ll want to add some liquid dish detergent and use a cloth. Start washing from the top, and work in small sections downward.

Keep the surface wet, and do not allow the soap or cleaner to dry on the siding. Continually rinse the surface until all soap is removed. Mold, moss, or algae on your siding? Well, now we’re going to need a little elbow grease in addition to the soft cloth and water.

As always, adhere to warning labels on any products you may be using. If you have cedar siding, never use siding cleaners that contain chlorine bleach (sodium hypochlorite). Harsh cleaners are bad for your siding, as well as plants and trees that may suffer from overspray. One alternative is to use oxygen bleach on your wood siding.

Happy cleaning!

Joseph Ketner Construction: Portland Siding Replacement Contractor

Joseph Ketner Construction is widely recognized for superb workmanship, stellar customer service, and attention to detail.

We also take care to utilize eco-friendly methods whenever and wherever possible. We recycle wood and metal products. Our caulking and paint products are lifetime-rated. And we’re an EnergyTrust of Oregon partner.

Get in touch with us today to see what we can do for you.

Joseph Ketner Construction
3515 NE 43rd Ave
Portland, OR 97213

OR #148082
WA # KETNEJ*984MP