HI, my husband and I have a second home we are trying to sell. However when a possible buyer came to look at it with a contractor friend, he said that it appears that there was a possible leak coming through the back door under the vinyl. And that the problem is caused because the deck was built level to the first floor. There is a dark almost blackish discoloration on the vinly but it isnt bubbling or coming up in anyway and it almost appears as if the sun is the culprit and not moisture because it doesnt look like mold. When we lived there i had a mat near the door and never noticed anything but now that we havent been in there for almost 7 months the discoloration started to appear, which by the way the sun shines right on that area. Im just concerned that the deck is causing issues and that we will have to spend tons of money to lower the deck which is very large! Please give us some expert advice for we are definitely not experts. Thanx
You are seeing mold under the wear-layer of the vinyl, plain and simple. The sun is feeding the growth but is not the base culprit.
Obviously there is moisture intrusion coming from somewhere but this may be repairable by caulking on the outside. Caulk won't change the discoloration of the flooring it is basically ruined in this area. Why not cut out an area and install some ceramic tile to make a nice looking entry at this door?