White powder on brick and what it tells you

That white powder, haze or crust on brick has a name: efflorescence. It is salt. Brick, mortar and the soil around a house all hold small amounts of salts that dissolve in water. When water moves through a wall and comes out the face, it brings those salts with it. The water dries off into the air. The salt stays on the brick.

So efflorescence is a sign of water moving through the wall. By itself it is mostly a looks problem. What matters is how much water it takes to make it, and where that water is coming from.

Everything that makes efflorescence is here in good supply. Rain comes often and hard. Air off the bay carries salt that settles on walls near the water. Storms push water deep into brick. Lawns get watered every morning, and the ground stays damp around the slab. Brick here spends much of the year getting wet and drying out again, and each time it dries a little more salt comes out.

It often shows up after a long wet stretch, once the sun finally comes out and the wall starts drying. That is why a wall can look clean one week and white the next without anything new going wrong.

Brick and mortar on a new house or a fresh repair often show some white in the first months. The wall is giving up the water and salts it was built with. This kind usually fades as the wall dries and the rain rinses it off. It is not a sign the work was bad. If it is still coming back strong long after, that points to water getting in from somewhere.

Where the white sits on the wall tells you where to look. A few common patterns on Mobile houses:

• A white band along the bottom few rows: ground moisture wicking up, splashback, a sprinkler, or blocked weep holes holding water behind veneer
• A patch under a window: a leaking sill, open joints below it, or failed caulk around the frame
• A streak down from the roof line: an overflowing gutter or a gap where the roof meets the wall
• White on the chimney below the top: a cracked crown or open joints letting rain in from above
• A spot around a downspout or hose bib: a leak at the fitting soaking that part of the wall
• White on brick piers or foundation walls under a raised house: damp ground and poor drainage underneath

Not every white mark is the same thing. A hard white crust running down from a joint, the kind that will not brush off, is usually lime that water has carried out of the mortar and left behind. It needs a different cleaner, and it means water has been running through that joint for a while.

Gray, green or black film on a shaded wall is mildew or algae, not salt. And a gray haze on new work can be mortar left on the face from the job.

On a dry day, brush the powder off with a stiff brush with natural or nylon bristles. Sweep up what falls so it does not wash back into the bed. A lot of the time that is all it takes.

Skip the hose and the pressure washer for this. Water dissolves the salt again and carries some of it back into the brick, and high pressure can damage the brick and the joints. Skip wire brushes too. Steel bristles can leave tiny bits behind that rust and stain the brick.

Strong acid cleaners are a last resort and a job for someone who knows brick. They can burn the mortar, and on some brick they leave stains of their own that are harder to get off than the white was. If a cleaner is needed, use one made for efflorescence on masonry and test it on a small hidden spot first.

A clear sealer looks like an easy way to stop white stains. It can backfire. If the sealer keeps the salt from reaching the face, the salt dries just under the surface instead. There it grows and pushes, and the face of the brick can flake off. That is spalling, and it is a much bigger repair than a little white powder. The guide on why brick spalls goes into it.

Most efflorescence is a reminder to watch the water. It is worth a closer look when:

• It keeps coming back heavy in the same spot after you brush it off
• Brick faces near it are flaking or popping off
• The mortar in that area has gone soft and sandy
• There are stains, a musty smell or soft drywall inside on that same wall
• It shows up in the attic or a closet on the back of a chimney
• It sits in a band along veneer where the weep holes are buried or blocked

Any of those means water is getting into the wall faster than it can dry out. Once gutters, downspouts, sprinklers and soil are sorted, what is left is usually masonry: open joints, cracked brick, a bad sill or a cracked chimney crown.

Brick Repair and Renovations does that kind of brick repair and tuckpointing in Mobile, and Donald looks for the water behind the stain before fixing anything. The brick repair page and the tuckpointing page cover the work. Text a photo of the white spots and the wall around them to (251) 305-5966 with your part of town.