Moss on siding, do I need to replace this siding before painting?
You can save the siding, but kill the moss off first with a product you can get at the big box stores. Many products claim it will keep a roof clear of moss for 2 years. It will take a few weeks after applying it for it to do its job. Do not power wash or scrub the roof!! After it is gone remove the loose paint, making certain the wall is clean before priming and finish painting.