Decks, Patios, Porches and Docks - Mildew?

My problem is with the underside of my porch. The porch is small (8 x 8) is about 5 feet off the ground. The support beams are old 2 x 10 boards. The porch is decades old and I'm sure not of pressure treated wood, however it appears to be in good condition and no visible signs of rot/decay. The entire underside of the porch has darkened so much it's almost black. I'm sure this is due to moisture. Is there anything I can use to spray the underside to stop mold from deteriorating the wood?

Welcome to the forums!

A bleach water solution, applied with a pump up garden sprayer will remove/kill the mildew. If it's real bad it will require several treatments - scrubbing will help.

Applying a good exterior stain will slow down the reoccurance of mildew. There are mildewcide additives that can be added to the stain. There is a mildewcide already in the coating but the underside of the deck might benifit from more. I wouldn't advise staining the bottom side of the deck without first making sure the top side is coated with a good deck stain.

Spraying on Mold*Off works great as an inhibitor and cleaner.www.moldoff.org. Cleans and stops from growing for extended period of time.