How to remove ash buildup from fireplace bricks

Q:How can I remove wood ash from fireplace brick?

Gaithersburg, Md.

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A:From the picture you sent, it looks as if you’re dealing with ash, soot and a little charcoal — ash being the white and gray fluff, soot being the black stains and charcoal being the black lumps. If you want to get the fireplace as clean as possible, you need to remove all three. If you just want the bricks outside the firebox to look clean, you’ll probably still want to remove most of the remains and push the rest toward the back while cleaning, so you don’t end up with a gooey mess. You’ll need to introduce water to remove the soot.

Wait at least 24 hours after your last fire to begin. Even then, be aware that many house fires have started because people have shoveled what they thought were cold coals into bags or boxes that they left inside, only to discover after the fire started that some live coals must have been in the mix.

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Never put fireplace ash into combustible containers or leave even a metal bucket filled with ash where it could ignite a building if flames were to erupt. If your fireplace has a metal door to an ash pit, push the ashes down that hole and have a chimney-cleaning company empty the pit during your next cleaning. You can also shovel the ashes into a metal bucket or a metal ash bucket with a lid to keep them from spilling as you go outside. (The UniFlame large-capacity ash bin with lid and shovel is $65.18 from Home Depot.)

No matter how careful you are, you will inevitably stir up fine dust. Wear a respirator, such as an N95. If you have a heating system that circulates warm air, switch it off beforehand, so you don’t spread dust.

Safety experts warn against using a household vacuum to clean out a fireplace. If an ember is still live, it can burst into flames because of the swift airflow, and household vacuums aren’t built to contain fire. Also, ash contains particles small enough to pass through filters on standard vacuums, so they can clog the motor and get spewed out into your house along with the exhaust air. But if you have a vacuum with a high-efficiency particulate air (HEPA) filter, which traps very fine particles, and if you use the vacuum just to clean out the final bits of gray ash embedded in the texture of the bricks, there should be no fire hazard. (You would stir up less dust than if you tried to loosen and remove the ash remnants with a whisk broom.)

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How to remove ash buildup from fireplace bricks

Another alternative is to invest in a vacuum specifically designed for scooping up fireplace ash, such as the Snow Joe 4.8-gallon ash vacuum ($54.47 on Amazon). Using an ash vacuum makes removing the ash much tidier, and it can clean corners and crevices. But make sure you read the instructions. The Snow Joe, for example, has a metal can and nozzle, but the instructions make it clear that it’s safe to use only if the ash is cold. Because there can still be live embers even when you think the ash is cold, the instructions warn to set the vacuum on a fireproof base while using it and to feel the hose and container while cleaning to ensure they are not heating up. If you sense heat, stop vacuuming and move the vacuum outdoors, away from buildings and fences.

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If you use an ash vacuum, treat the remains as if you shoveled them into a metal bucket. Empty the ash outside promptly, and leave even a covered metal container where a fire wouldn’t cause damage. After a few days, dispose of the ash with your household trash or as your community’s solid-waste program recommends. Some communities allow ash in bins for garden waste, while others do not.

If you have a garden with acidic soil, you might want to sprinkle the ash thinly on your garden. Wood ash contains calcium, magnesium, potassium and trace elements that can boost plant growth, which helps plants grow after forest fires. But ash is alkaline, so if your soil is already alkaline, don’t add ash except where you want higher alkalinity. For example, if you have blue hydrangeas and want pink flowers instead, adding ash could make that happen.

Once all the dry material is cleaned away from your bricks, you can work on removing the soot stains. Soot is oily but can usually be removed using a grease-cutting detergent in water. The Brick Industry Association trade group recommends first saturating the bricks you want to clean with water. Dry bricks absorb whatever liquid is applied, and if that’s dirty or soapy water, it can become difficult to rinse away. To spread the water — and eventually the cleaning solution — use a masonry sponge, a kind made for cleaning grout, because it holds more liquid and more dislodged grime than an ordinary household sponge. The QEP multipurpose scrubbing sponge is $2.72 from Home Depot.

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For the cleaning solution, start with whatever clear dishwashing soap you have. If that doesn’t give you good results, buy a cleaner labeled for use on brick. Scrub with a fiber or plastic-bristle brush, not one with metal bristles. Then rinse several times, using the masonry sponge. Rinse and re-wet the sponge with clear water as you go.

If you bought an ash vacuum, you might think vacuuming up the dirty water would work better than using a sponge. But read the instructions. Ash vacuums look like shop vacuums, but they are not safe to use for vacuuming liquids. Use an ordinary wet/dry vac.

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