How to Clean the Black Edges on Your Carpet

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Here is why the edges of your carpets turn black and dingy, plus how to get them clean again and then keep them that way.

Overhead of a vacuum cleaning the black edge of a carpet at the base of a wall.

Have you ever noticed the edge of the carpets look darker than the rest? Maybe you shampooed your carpet, hoping to get rid of them, but those black lines are still at the base of your walls.

The good news is that this problem doesn’t mean you’re bad at cleaning or that your home’s a mess. A dark area on carpet edges is a common problem even in the cleanest homes. The bad news is that vacuuming isn’t enough to eliminate them. But you can get them out with effort, and below you’ll also learn steps to help prevent their return.

Why Do the Edges of Carpets Get Black?

Those dark lines on your carpet around the baseboards and skirting boards are called filtration soiling or draught marks. They happen because your HVAC or ventilation system forces air into rooms faster than it can exit. When air can’t escape through returns or doorways, it will seep through gaps beneath baseboards and stair treads. Your carpet acts as a giant filter sifting the escaping air, so ultra-fine dirt particles get caught on carpet fibers as the air passes. When this happens over a significant amount of time, it leads to dark areas at the base of your walls and doors.

Those Dark Lines on Carpets Keep Getting Worse

If your home is older, you’ll have more problems with black lines forming on the edges of your carpet. That’s why builders now install a gasket or strip of closed-cell foam where the wall and sill plate meet. They also use a housewrap beneath siding and foam insulation where pipes and wires enter the home. These measures minimize how much air flows into your home through gaps and significantly reduce filtration soiling.

How to Clean Dirty Edges on Carpets

Cleaning filtration soiling isn’t a quick chore, so many homeowners hire professionals. Not all carpet cleaning employees are trained to clean draught marks properly, though. Unfortunately, you won’t know this until you’ve paid the bill because carpet stains can reappear after the carpet dries.

If you want to eliminate the black lines on your carpet edges yourself, follow the steps below. You’ll need to set aside an afternoon for each room or work in sections if you prefer.

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Materials Needed

  • A vacuum cleaner with crevice tool and brush attachment
  • Scrub brush
  • Baking soda (bicarbonate for UK readers)
  • Spray bottle
  • Water
  • Hydrogen peroxide or rubbing alcohol
  • White cloths

Steps to Remove Filtration Soiling on Carpet

1. Vacuum: Use the crevice tool to clean the dark area at the edge of your carpet. Then, switch to the brush attachment and vigorously brush the area to loosen any sooty residue.

2. Absorb: Sprinkle a thin layer of baking soda on the dark line. Use the scrub brush to rub it into the fibers to bond with the sooty carbon soil. Wait an hour, then vacuum it with the crevice attachment.

3. Spray: In the spray bottle, combine 3 parts water with 1 part hydrogen peroxide (for light carpets) or rubbing alcohol (for dark carpets). Mist a 3-foot section of the rug just enough to dampen the fibers. Do not drench the area, or you’ll get the underlay wet, which can destroy the adhesive.

4. Blot: Use a clean white cloth to blot the dark streak on your carpet. Change cloths as needed, so you’re always working with a fresh section of fabric. Do not rub. Let the area dry for at least 24 hours, and then vacuum again with the crevice attachment.

5. Shampoo: For best results, shampoo your carpet using hot water and a carpet steam cleaning method that involves detergent to remove additional grease and white vinegar to leave your carpet cleaner all over.

How to Keep the Edges of Carpets from Turning Black

It’s important to understand that vacuuming isn’t enough to eliminate those dark lines on your carpet’s edges. If your home has an HVAC system, filtration soiling is bound to occur. But there are steps you can take to minimize or delay it.

1. Vacuum often. The less time filtration soil sits bonding with your carpet’s fibers, the easier it is to get out. So, vacuum and use the crevice attachment at the base of your walls at least once a week. Also, make sure you know how to vacuum correctly, so you’re getting all the dirt out.

2. Don’t add pollutants to your home’s air. Open your windows daily for at least 10 minutes to allow fresh air into your home. Don’t smoke indoors, and run your stove’s hood filter fan when you’re cooking. Keep your range hood filter clean, so it works properly, too. Choose soy candles, which produce very little soot, and trim candlewicks before burning them. Clean your fireplace and have the chimney inspected annually to ensure no creosote blocks the flue.

3. Keep dust under control. The less dust in your home’s air, the fewer particles collect in the carpet at the base of your walls. So, reduce dust in your home by routinely cleaning soft furnishings, curtains, and carpets. At least once a year, have your home’s HVAC system inspected and cleaned. Change your furnace filter monthly and clean your home’s air ducts and registers seasonally to reduce how much dust your system blows around.

Keep in mind that there’s no avoiding filtration soiling as long as you have an HVAC system and carpeting. You can buy a new carpet, but eventually, it will develop black edges around the base of the walls, too. When ready for new flooring, switch to wood, tile, or LVP and use area rugs as needed for comfort. You’ll no longer have black edges on your carpets, and your home will be much easier to clean.


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