We just had a new cedar deck installed and they used a water based stain. After it was stained it rained a few days later and some black spots started appearing in a couple different areas. It is not everywhere just in a couple locations. Seems strange that it wouldn’t be everywhere. One location is really bad.
Could it be related to water coming off the roof? I’ve seen several ways to clean this online but won’t it just happen again?
Thanks for all your help!