What road salt does to stone steps, walks and stoops, and how to go easier on them

Salt comes from more places than the bag

Most people think about the salt they spread on the front steps. But steps and walks take salt from all over. The city plows throw salty slush onto the boulevard and the end of the driveway. Cars carry it in on their wheels and drip it onto the garage floor and the apron. Shoes track it up the steps and onto the stoop, where it melts and runs into the joints.

So the masonry nearest the street, the driveway and the garage door usually takes the most. Stone steps that meet a salted walk, the bottom of a stone wall along the driveway, and the landing outside the side door can sit in salty meltwater for months.

What the salt does once it is inside

Stone, brick, mortar and concrete all have tiny pores. Salty meltwater soaks into them the same way plain water does. But salt pulls moisture out of the air, so salted masonry stays damp longer after every melt, and damp masonry is the kind the frost breaks.

Salt also means more thawing. It melts ice on the surface on days when the stone just below is still frozen. The meltwater runs into the pores and the joints, and by night it freezes again. A step that would have stayed frozen and quiet for a week gets worked over every day.

Then there is the drying. When salty water dries out of the surface, the salt stays behind as crystals. If they form right on the face, you see them as a white crust. If they form just under it, they grow in the pores and push outward, and the face lets go in thin flakes.

Soft stone like limestone and sandstone shows it fastest. Dense granite holds up better. Old brick spalls, mortar joints wash back, and concrete steps lose their top skin until the gravel inside shows. Metal railings set into stone steps rust in the salt, and rust takes up more room than the steel did, so the stone around the post cracks.

The signs on your steps and walk

Salt damage has a pattern, and once you know it you can spot it from the sidewalk.

• White crust along the joints and the bottom edge of the steps that comes back after you scrub it
• Thin flakes coming off the face, worst at the front edges of the treads and on the bottom step
• Treads that have gone rough and sandy where they used to be smooth
• Joints washed back on the lower steps while the ones higher up still look fine
• Cracks in the stone around railing posts, often with rust stains
• Damage that is worse near the driveway, the walk or a downspout than on the far side of the same steps

White stains from outside and from inside

Not every white stain is road salt. Water moving through any masonry picks up natural salts from inside the stone, brick and mortar, and leaves them on the face as it dries. Masons call that efflorescence. It shows up on walls nowhere near a salted walk.

Road salt tends to sit in a tide line low on steps and walls, at the height the slush reached, and it is heaviest near the street and the driveway. Efflorescence shows up wherever water is coming through, often under a sill or a cap, or in a patch on a foundation.

Either way, brush it off dry with a stiff brush, then rinse with plain water once the weather warms. Do not use acid cleaners on limestone or marble. Acid eats the stone itself. If the white keeps coming back in the same spot season after season, water keeps getting in there, and that is worth tracking down.

Going easier on them in winter

Nobody is going to stop salting their steps in a Minnesota winter, and a fall on ice is worse than a flaked tread. The aim is to use less and let it sit for less time.

• Shovel early and often, so there is less packed snow and ice left to melt
• Spread salt thin where it is needed, then sweep up what is left once the ice is gone
• Use sand or grit on steps for grip. It does not melt anything, but it does not soak in either
• Do not throw salty snow from the driveway onto the steps or pile it against stone walls
• Use a shovel with a plastic edge on stone treads so the edges do not chip
• Fix a gutter that drips onto the steps, since that is where the ice keeps building back

Which deicer to buy

Products sold as gentler on concrete or stone still put salty water into the surface. Some do less harm than plain rock salt, and they can be worth the extra cost on old limestone steps. But how much you put down matters more than which bag it came out of.

Read the label for anything that says it is not for new concrete or not for natural stone, and keep any deicer off fresh mortar from a repair.

Rinsing in the spring

Once the nights stay above freezing, give the steps, the walk and the bottom of any stone walls a good rinse with a garden hose and a soft brush. That washes out the salt sitting in the surface before the spring rains drive it deeper.

Skip the pressure washer on stone steps and old mortar. Up close it can cut soft mortar out of the joints and scar the face of the stone. A hose and a brush is plenty.

After the steps dry is the best time to look them over. Clean stone shows flaking, open joints and cracks much better than stone with a winter of grime on it.

When the steps need more than a rinse

Some damage is past what a hose can help. Flaking that goes deeper each year, treads that rock, joints open on the tops of the steps, a step that has tipped toward the house, or stone cracked around a railing post all let more water in, and the next winter makes them worse.

Stone steps and landings can often be put right without starting over. Loose treads can be lifted and reset, open joints repointed, and a broken piece replaced with stone that matches as close as it can. The stone repair page on this site covers how Don Barger at Stonecrete Inc resets loose stone and repoints joints, and how he looks for the cause, whether that is salt, frost or water running the wrong way.

If your steps are brick or concrete, ask Don about them. Call or text (612) 432-9467 with a photo of the steps from the walk and a close one of the worst tread, and say what town you are in.