Name:   froghog - Subject:   Mildew Date:   12/1/2018 7:08:16 PM (updated 12/1/2018 7:14:04 PM)

Like others said find the leak. What I use to clean and kill mildew is;  In a 5 gal bucket pour 3 gal water- 1 gal bleach- 1 cup TSP- and 1 cup liquid laundry detergent. Stir it up till all the tsp is desolved in the mix. I use this for and mold or just as a cleaner, like my shower.I use this with my pressure cleaner on the wash setting. After using this let the surface dry and  then rinse thoroughy with clean water. You should be able to paint or stain after one treatment but if its a bad stain it might take more than one treatment. Make sure the surface your painting or staining doesn't have a residual powder from the tsp if so just wipe it with damp cloth. Hope this helps.

PS Please wear old clothes and hat with eye protection and rinse if any get on skin.