Can Costco Laundry Detergent Really Clean Vinyl Siding?

Many people love Kirkland laundry detergent — Costco’s signature brand — including those at Consumer Reports, which selected this brand as the best value among competing products. Henkel, the German company responsible for making it, announced in 2022 that it was divesting its retail brands in the U.S. and selling them to another company, so the product may change. But while it’s still on the shelves in its current form, you might consider it for cleaning things other than laundry. So, can you clean siding with Costco laundry detergent?

Actually, siding is a great candidate, according to our experts for cleaning with Kirkland laundry detergent. “It is safe to use and has no chemicals which will damage the siding,” says Derek Christian, who owns a home cleaning company. Scott Schrader, another cleaning expert, largely agrees, but cautions “there are some pros and cons to keep in mind.” Here’s what you need to know about cleaning siding with Costco (Kirkland) laundry detergent.

What’s In Costco Laundry Detergent?

A glance at Costco’s Materials Data Safety Sheet reveals a comforting fact about Kirkland Signature Heavy Duty Laundry Detergent: It doesn’t contain phosphates, which means it probably won’t hurt the vegetation surrounding your house or contaminate the water table. Also reassuring: “It has no chemicals which will damage the siding,” according to Christian.

The unscented variety, which comes as a liquid, contains mostly salts and alcohols, along with fatty acids, which act as surfactants, a brightening agent and limonene as a freshening agent. Scented varieties contain a long list of other chemicals, but you probably wouldn’t want to use scented detergent to clean your siding anyway, so it’s best to stay away from those to protect your plants.

Can You Clean Siding With Costco Laundry Detergent?

Sure. “Laundry detergent has also been used for decades to clean heavily soiled places like concrete at gas stations,” says Christian, so there’s no reason why it won’t make short work of your vinyl siding. Schrader adds that Kirkland detergent is “a very powerful cleaning product designed to remove stains and grime that are often stuck to vinyl siding, building up from dirt and mildew.”

Why It Works…

“Many clothes are made out of plastic fibers, much like what your siding is made from,” explains Christian. Because laundry detergent is designed for clothes, it works great on stains common in laundry like oils and dirt, but there are caveats.

When It Doesn’t Work…

“A common reason for cleaning siding is to remove either black mold or green algae. To remove these, you need something that will kill the organic materials, like hydrogen peroxide or bleach.” Kirkland detergent does not contain any such chemicals, but you can add them when mixing the detergent with water to make your cleaning solution.

Besides this, Schrader points out another problem: “Detergent may leave residue or even discolor your siding if you do not rinse the siding to completely remove all of it.” That means that using too much detergent, or failing to adequately dilute the detergent, can damage your siding and potentially allow for residue to build up over time.

Should You Clean Your Siding With Costco Laundry Detergent?

Can you clean siding with Costco laundry detergent? Sure. Should you? If saving money by getting the job done with stuff you already have around the house is a top priority, why not? But you’re going to have to work harder, because Schrader cautions against using high-pressure washers with Costco detergent, “as it is likely to damage siding.” That means scrubbing by hand, so if that doesn’t sound appealing, you’re better off sticking with detergents specifically designed for cleaning surfaces with a pressure washer.

Schrader’s recipe for mixing is to add about a cup of detergent per gallon of warm water. Keeping in mind that, as Christian point out, laundry detergent won’t kill mold or algae, include about half a cup of bleach, isopropyl alcohol or hydrogen peroxide as a disinfecting agent. Scrub gently with a cloth or soft-bristle brush (wear gloves) and don’t forget to rinse thoroughly with a garden hose to prevent residue buildup.

About the Experts

• Scott Schrader is the Chief Marketing Officer at CottageCare, a leading home cleaning company with over 41 locations nationwide.
• Derek Christian is the Co Owner of All Star Cleaning, one of the largest home cleaning companies in America. Derek has cowritten the book and testing program used to certify home cleaners by the trade association, ISSA.

Sources

• Consumer Reports: Best and Worst Laundry Detergents of 2025; (2025)
• The U.S. Sun: Costco fans in frenzy after ‘legendary’ product set to be discontinued for good – but a rival has stepped up its game; (2025)
• Costco Wholesale: Kirkland Signature Cleaning Products – California Cleaning Product Right to Know Act; (2025)

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