About two years ago I had an L shaped area finished in the center of my basement -sheet rock ceilings. Builder used green board for all the sheet rock work. HVAC guys ran a few returns and heat and air in the finished area. Exterior Basement walls in this 7 year old house are poured concrete. There is a closet sized unfinished room with a door that remains closed off the finished area. 3 walls of this small room are poured concrete and the other wall with the door is sheet rock. This small room contains the breaker boxes and also has plumbing to support the washer directly above on the 1st floor as well as the outside faucet. This room is becoming moldy. The wood joists are turning green. There is a small gap above the circuit boxes that would port into the space above the finished areas ceiling space that runs wires and cables. My questions are 1. how do we clean and stop permanently this small room from growing moldy and 2. have we now introduced mold to the sheet rocked area via the small gap that exists between the two rooms and if so what do we do to neutralize ? Thanks much.

Bleach is the mold killer, but you probably have mold on the back sides of the walls and ceiling by now. I had to rip all mine out, under the kitchen, which was a never ending series of leaks from every ancient appliance and valve.
I would suspect the outside faucet first if you don't shut off the supply to it every fall and leave it open and are in a northern climate, and would look for a misting leak, since you don't say you see water pooling below.
But washers can start leaking slowly too. Drains too. Might as well rip it all out.

If there is no ventilation to this room and the door is kept closed, it is possible the mold issue is from humidity being too high. Do you have a basement dehumidifier? Without adequate ventilation, particularly in a basement and in the south, where I am located, you need a dehumidifier or a HVAC vent in the room. I would start with bleach and ventilation before I'd start tearing out drywall.

This is a basement closet. Confirmed mildew on joists. Service guy suggested Boric acid for cleaning the wood and dehumidifier. Are self draining dehumidifiers able to pipe the moisture up and out vertically ? Is this through a condensate pump ?

You might run a mold test to see if it is toxic and then choose a plan of action based on the kind of mold it is. There is also some natural mold and mildew removal products on the market that you may want to do an online search.

-JohnABQ
<a href="http://moldtestkits.gotohomerepair.com/the-e-z-mold-test-kit-and-info-for-the-easy-to-use-air-sampler/">mold test kits</a>

You might run a mold test to see if it is toxic and then choose a plan of action based on the kind of mold it is. There is also some natural mold and mildew removal products on the market that you may want to do an online search.

-JohnABQ mold test kits (http://moldtestkits.gotohomerepair.com/the-e-z-mold-test-kit-and-info-for-the-easy-to-use-air-sampler/)