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 enter image description here 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 enter image description here

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

2 Answers 2


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.

  • I really don't know what to say about it. I am really worried since this seems to be part of an ampler problem. Please read more here
    – MiniMe
    Sep 22, 2014 at 20:34
  • Somebody on another site indicated that this might be water getting out because it is accumulated below the grade. Can this be the case?
    – MiniMe
    Sep 23, 2014 at 16:15
  • @user2059078 Efflorescence can happen any time the cement gets wet, there's no way to tell if it's water from rain (normal) or from accumulated water due to inadequate drainage.
    – Zaralynda
    Sep 23, 2014 at 16:34
  • The interesting part, if I could say so, is that the phenomenon is more accentuated on the side where the patio is. In the picture you can see that the crack extended toward the window but that is the only sign of that sort on that side. There is more smaller cracks like you see in the second picture on the wall facing the patio
    – MiniMe
    Sep 23, 2014 at 17:28

I work on a house with similar problems. The basement was damp(er) and the grass wasn't properly graded away from the house. It had an incorrectly pitched patio which we poured 4" of concrete over, giving it a new 1/8" pitch. We add more dirt around the house every few years and we have to pack it around the foundation each year, back against the house. It heaves from freeze\thaw to a noticeable gap.

Your pictures show evidence of where the patio runs along the house, that this has been addressed before. The brick has sunk below a grout job seen attached to the house. Whatever water doesn't sneak into the patio gets funneled to the grass and into your house. If you're not going to dig a perimeter drain (and increase the grade) or have your foundation professionally sealed, regrading the soil around your house and resolving the patio issue would be great improvements. Install a bathroom exhaust fan to keep some air moving in the basement and also, keep your gutters clean (same house, yearly chore).

  • There is something that I don't understand about this problem. It has been dry for about two weeks now, no rain at all. The dark gray spots around the cracks don't go away. By the their look you would say that they are wet but not when you touch them it does not feel like that. I will have to see what meant to grade the patio, I guess this means removing the pavers and adding more sand. What I can't figure out is how the patio will look after being graded. The other problem that I have is working under the deck ... especially if I have to waterproof that would be a big issue
    – MiniMe
    Oct 1, 2014 at 11:21
  • Digging an surface french drain will also be problematic with the patio there and with nowhere to drain that in the backyard My biggest fear is that I might achieve nothing with a surface french drain because I think that the water might get to the wall via underground. We are talking about clay soil here which supports the water in its horizontal migration rather than allowing it to go deep into the ground
    – MiniMe
    Oct 1, 2014 at 11:22
  • Does anybody know why the dark grey spot never dry to say so? They look like wet spots but if you touch then it does not feel like they are wet. I have seen the same on the concrete slabs in front of my entrance door. There is no cracks there, the slabs are intact but they have certain areas (mostly at the edge) where they have dark spots like above which get bigger when the weather turns humid (ex it is about to start raining) Can anybody explain this?
    – MiniMe
    Oct 3, 2014 at 17:24
  • concreteconstruction.net/concrete/… @user2059078
    – Mazura
    Oct 3, 2014 at 17:45
  • If that explanation fails you, concrete with spots that are more porous will darken differently. You could use concrete sealer. @user2059078
    – Mazura
    Oct 3, 2014 at 18:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.