Robert Lamoureux | What’s that residue on the concrete?

Robert Lamoureux
Robert Lamoureux
Share on facebook
Share on twitter
Share on email

Question No. 1: Hello, Robert. I noticed that when we had the first hard rain, water came under my garage door. When I opened the door after the rain had stopped, there was like a white residue where the water had been. Was this from the rain? Also, some of the concrete seems to be turning to bits/pieces/powder where it rained. Does this mean I need new concrete in those areas or a whole new garage/driveway floor? Thanks, Mary B. 

Answer No. 1: Mary, thank you for writing in. No, the white residue is phosphorus, which is the minerals in the water that are coming up through the concrete. This is very common after rain. You can either brush it off or wash it down with a hose. It may come back once or twice but when the earth dries out it will not come back. 

Question No. 2: Hi Robert, thank you for sharing your expertise in The Signal. I have a roof question. We live in a one-story home, built in 1978. The roof was replaced after the 1994 earthquake with concrete tiles.  

We need to replace the roof now because the paper is failing. My question is about the weight of these tiles. Were our homes built to have this much weight on the roof? Do you recommend any lighter roofing material, or should we put these tiles back on? Do you have any experience with the California Cool Shingles? Thank you! I know you can’t recommend workers in the paper, but I would appreciate any local roofer recommendations.  

— Karen N. 

Answer No. 2: Karen, when the concrete tiles were installed, were they replacing concrete tiles or was the roof asphalt shingles, then to concrete, do you remember? If the original were asphalt, were there permits pulled to go to concrete? If yes, then you can go back to concrete. If not, it should have been engineered at the time of replacement to be sure the roof can take the loads. 

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].         

Related To This Story

Latest NEWS