How to Remove Mold from Floor Joists

Floor joists under the floorboards of an old house.
  • 1-2 hours
  • Beginner
  • 0-125
What You'll Need
Spray bottle
White vinegar or liquid bleach
Step ladder
Clean rags
Plastic bag
Extension cord
Drop light
Respirator mask
Safety glasses

If you live in a humid and moist climate, it's common for mold to form in places throughout your home, including your floor joists. This can happen not only to homes with basements, but also to those with crawl spaces. If left alone, mold in joists can eventually become such a problem that it can only be removed by professionals. The best course of action is always to remove any spores in the earliest stages of development, so follow the simple steps below to effectively get rid of all of it.

Step 1 - Mix a Solution of Water and Vinegar

Compare mold cleaners on Amazon.

In a spray bottle, mix a solution of 10 parts water and one part white vinegar or liquid bleach. Please note that if you use bleach, make sure to get a container that will allow you to pour the solution without spilling it, as it can easily damage clothes or other belongings. Wear a respirator mask and if the work area has any windows, open them to get proper ventilation while using the bleach.

Step 2 – Apply the Anti-Mold Solution

Adjust the spray bottle to a mist setting and douse the mold spores; if you use a more forceful stream of water, you might scatter mold spores when you spray them. You'll need to get the spray bottle within inches of the affected area for it to be effective, so when treating areas in your basement, you will likely need a ladder to reach higher levels of joists. When applying the solution, be sure to avoid spraying directly over your head to prevent getting the solution or mold spores from dripping on your face or head. Wear safety glasses to be extra careful.

Step 3 – Wipe Down the Sprayed Area

Use a clean, absorbent rag to wipe down the area you've sprayed with the solution. Make sure to get a clean rag for each new areas, as this will help avoid spreading the spores. Discard the used rags into a plastic bag when you're done for proper disposal.

Step 4 – Spray Additional Applications of Your Solution

After wiping down the mold, add a second application of the solution you've made, and allow it to sit for 24 hours. Mold is a persistent grower and it will come back if neglected, so continue with the same process of spraying and wiping for three more consecutive 24-hour periods. Then, wait for a week, and repeat then entire process for another three days, discarding your used rags in the plastic bag each time they are used.

Step 5 – Treating Floor Joists in Crawl Spaces

In crawl spaces where lighting is more dim, take an extension cord and a drop light with you as you inspect the floor joists for mold. Grab a helper for this task if you can. It will be safer to have someone else who can direct the light while you spray and wipe, and you can focus on doing a more thorough job in the meantime.

When you purchase through links on our site, we may earn commissions at no cost to you.