Question: Hi Robert, you have helped me in the past and hoping you can do so again. I have forwarded you a picture of my driveway and will send you another picture in another email. I am not very technical on computers, sorry. Can you tell what these marks are on the driveway? They look like water marks to me, but are on the concrete all the time, not only after rain. Also, in the next picture the concrete turned dark in some places near the garage door. I would like to know what I should do about this, if anything.
Thank you so much for helping me out now and in the past, I read your articles every week and learn a lot. Look for the next email and the other picture. Barbara O.
Answer: Thank you for being a loyal reader. The white substance I see is phosphorous, which are mineral deposits in the water. Just broom or wash that down — it isn’t an issue. This is typical after rains have occurred — static pressure pushes the water up from out of the ground and leaves the mineral deposits like you see.
It can happen during non-rainy times as well, likely if the area is low-lying. This is very common; we even see this inside garages, generally if the moisture barrier, the visqueen, is compromised. The good news is that it looks like this is cosmetic only.
Robert Lamoureux has more than 40 years of experience as a general contractor, with separate licenses in electrical and plumbing contracting. He owns IMS Construction Inc. in Valencia. His opinions are his own, not necessarily those of The Signal. Opinions expressed in this column are not meant to replace the recommendations of a qualified contractor after that contractor has made a thorough visual inspection. Email questions to Robert at [email protected].