Below is a picture of one of the corners of my house
You can notice the white mineral efflorescence that formed on the wall
The patio starts just off that wall, quite a large one, rectangular shape parallel with the house
Here is another example near the same area (~ 2 feet distance) This one is vertical.
There are a couple other areas like this but a lot smaller, you can guess them in the second picture. They seem to be crack but under the surface of that stucco or whatever is the name of that cement cover
The patio looks wet because it rained heavily today.
I am just wondering if this is bad. We recently bought this house. The house has gutters but I think that ocassionally that wall is washed by the rain
Best Answer
Generally in housing, the white marks (efflorescence) is caused by salts in the cement washing out to the surface when wet, and being left behind when the water evaporates.
If there's any salt being added to the system (I did some research in college on a brick wall built with seawater exposure), then over time the efflorescence can be part of the system that will cause the cement to break down over time.
However, if your patio is inland and you don't use any salt on it (like de-icers) then the efflorescence is cosmetic and fairly harmless. If it bothers you there are chemical solutions (bleaching agents) that you can find at the hardware store that can remove efflorescence. They will not prevent it from coming back, it will continue to effloresce until all of the salts are removed from the cement.