Outdoor

Rock salt vs. calcium chloride: which ice melt should you use?

By Roof & Router Team. Updated October 15, 2026.

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Which ice melt should I use?

Start with the pavement temperature and what the deicer will touch. Shovel first, then pick from this table. Temperatures are the lowest practical pavement temperatures from the University of Minnesota’s Smart Winter Salt guide.

How cold can each ice melt work?

Each deicer stops working below a certain temperature. That limit is for the pavement, which can differ from the air.

Sources disagree on CMA. The Minnesota table lists 20°F, while Iowa State says it works to about -15°F. Blends fall in between, depending on the main ingredients. Read the label to see what is actually in the bag.

How much ice melt should I use?

Far less than most people spread. The Minnesota Pollution Control Agency (MPCA) says about 12 ounces, enough to fill a coffee mug, treats a 20-foot driveway or 10 sidewalk squares. That is about 1,000 square feet.

University of Minnesota Extension adds these tips:

• Shovel or plow first. Do not put deicer on top of snow.
• Spread grains about 3 inches apart.
• Sweep up leftover salt on dry pavement.

By our math, a 20-by-50-foot two-car driveway is 1,000 sq ft, so one mug covers it. A 4-by-50-foot front walk is 200 sq ft, so about a fifth of a mug. Our snow shoveling safety guide covers clearing first without hurting your back.

Why it matters: UMN Extension says one teaspoon of salt can pollute 5 gallons of water. The MPCA says some Minnesota waterways now have so much chloride they are listed as impaired.

Does ice melt damage concrete?

It can, and new concrete is most at risk.

• First year: The National Ready Mixed Concrete Association (NRMCA) says to avoid deicing chemicals in the first winter, then use them in moderate amounts. The Pennsylvania Aggregates and Concrete Association says deicers should not be used on concrete less than one year old. Use clean sand for traction, and hose off salt that cars drip onto a new driveway or garage floor.
• Never use ammonium: NRMCA says never to use ammonium sulfate, ammonium nitrate or magnesium-based salts as a deicer, because they are “chemically aggressive and destroy concrete surfaces.” Ammonium compounds are common in fertilizers.
• Older concrete: The Pennsylvania Aggregates and Concrete Association says sodium or calcium chloride deicers are “generally considered acceptable” on good-quality dense concrete. It says products with magnesium chloride, potassium chloride, CMA or urea have been shown to cause much higher rates of deterioration.
• A caution on chlorides: A 2018 Federal Highway Administration brief says magnesium and calcium chloride can react with cement paste to form an expansive compound that damages concrete. Specimens soaked in sodium chloride showed no damage in the tests it cites.

The takeaway: on any concrete, use the least deicer that works. Concrete groups also recommend a silane or siloxane penetrating sealer to cut down on salt soaking in.

Is ice melt bad for plants and lawns?

Yes, especially sodium chloride. University of Minnesota Extension says salt spray can burn turf and evergreen needles. Salt in the soil dehydrates roots, and sodium compacts clay soil. Signs include brown needles and leaves, lost buds and branches, and plants dying early. UMass Extension notes damage may not show up until summer, or even years later.

To limit damage:

• Keep deicer on the pavement, not on beds or lawns.
• Do not pile salty snow around trees, shrubs or turf.
• Water heavily to flush salt from the root zone. UMass says this helps in well-drained soil but not in poorly drained soil.
• Wrap sensitive shrubs in burlap.
• When planting, keep trees and shrubs at least 3 feet from salted walks (UMN Extension).
• Near salted edges, choose salt-tolerant turf. UMN Extension says creeping red fescue does best and Kentucky bluegrass does poorly.

Sodium-free deicers like calcium, magnesium and potassium chloride are gentler on plants but still not harmless. Iowa State says magnesium chloride still damages plants when over-applied.

Is ice melt safe for pets and kids?

No ice melt is fully safe. Here is what animal and poison experts say:

• Paws: The ASPCA says treated surfaces can leave paw pads irritated, cracked or bleeding.
• Eating it: The ASPCA says the most common result is vomiting and diarrhea. Eating a lot can raise sodium levels and cause tremors and seizures.
• Calcium chloride: ASPCApro says eating large amounts can cause ulcers in the mouth and stomach.
• Urea: ASPCApro calls it the least irritating ingredient to a pet’s stomach.
• Labels: The MPCA warns “pet friendly” claims are unverified.

After each walk, wipe paws with a damp cloth or baby wipes, as the ASPCA advises. Booties or paw wax help too. Keep dogs from eating slushy snow near treated areas. Store bags out of reach.

For a child who swallows ice melt, the National Capital Poison Center says to wipe out the mouth, give a small drink of water or milk, and wash hands and face. Call Poison Help at 1-800-222-1222. For pets, call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435.

Does ice melt corrode metal?

Yes. Iowa State Extension calls sodium chloride and potassium chloride highly corrosive. It calls calcium chloride highly corrosive to concrete and metals. CMA is less corrosive, which is why UNL Extension notes it has been used on bridges sensitive to salt corrosion. UMN Extension also lists metal corrosion among the effects of excess salt, so using less near railings and steps helps.

Should I use sand instead?

Sand gives traction but does not melt ice, per the MPCA and UMN Extension. It is the right choice in two cases: below about 15°F, when rock salt quits, and on concrete less than a year old. Iowa State says sand and kitty litter do not harm plants. The downsides are that it gets tracked indoors and needs sweeping in spring. UMN Extension notes it can also clog drains.

Iowa State says a sand and salt mix also works, at about 50 pounds of sand to one pound of salt.

What happens if you buy the wrong type?

• Too weak for the cold: the MPCA says temperatures below 15°F are too cold for salt. Calcium chloride or sand is the fix.
• Too much product: the MPCA calls more than a mug per 1,000 sq ft wasteful. The extra runs off toward lawns, storm drains and local water.
• Any deicer on new concrete: risks surface scaling. Use sand that first winter.
• Fertilizer as ice melt: anything with ammonium sulfate or ammonium nitrate attacks concrete.
• A “pet safe” bag you did not read: check the ingredients. Urea, for example, stops working around 25°F.

Ice melt is one part of winter prep. See our winterize your house checklist and how to prevent ice dams on the roof.