Sometimes I wish we hadn't demolished our basement so we wouldn't have to worry about the problems we've found. Ignorance is bliss! But in the end we're glad we're uncovering the deeper problems in our house so we can make them right.
One of the problems we found in the basement is moldy walls. I'm not at all surprised, the insulation was done wrong and I knew it would mold eventually; that was one of the main reasons to demo the basement and start from scratch. Part of me was hoping the mold hadn't started yet and we could redo the walls before there was a problem. Unfortunately, the mold had started. Only five years after the previous owners had built the basement walls. It's a good reminder that converting a basement to livable space has it's risks and spending extra time and money to protect the walls from moisture is not only worth it but a necessity. Here are the worst spots.
The real problem
Mold needs three things to grow: Air, food, and water. Removing air from a living space isn't really practical and mold can eat most organic materials - wood, the paper from drywall, fiberglass insulation, even paint. There are some basement building systems that use mostly plastic and metal in an attempt to create an environment where there's no food for mold but most basements are still made from traditional materials that mold can grow on. The best way to stop mold is to try to control moisture which comes in two forms: humidity in the air and liquid water.
Air always carries some moisture in it, we call this humidity. Humid air tends to sink and usually finds its way to the basement. When humid air come in contract with cool basement walls it condenses into liquid water - it's the same thing that creates condensation on the outside of a cold glass on a hot day.
Condensation + food + air = mold. You can either build walls that are air tight so no humid air can't reach the walls, keep the walls warm so condensation can't happen by insulating the exterior of the house, or run a dehumidifier to keep the humidity levels low (below 60%).
Concrete might not look like it, but it's basically a big sponge. It contains water from the day it's formed and it's porous enough to let water in and out through capillary action. The key to keeping concrete walls relatively dry is to keep water as far from the walls as possible. Some ways to do this are as follows:
- Make sure your downspouts are clean and run water at least 6 feet from the base of the house
- Make sure your yard slopes away from the house. The dirt should slope downhill from the house at 2 inches per foot for at least 6 feet.
- Repair any cracks in the foundation
- Install a sump pump or french drain to remove water from inside the basement
We're working on a few of these things from the outside of our house that we'll share with you when we figure them out ourselves!
How to kill mold
Once the source of your moisture is removed, it's time to kill the mold that's living on the walls. There are a few ways to kill mold with some urban legends and mis-information mixed in. Here are your options:
- Ammonia or bleach - Either of these will work to kill mold but ONLY on hard, non-porous, surfaces like glass or tile. These will not work on wood, drywall, or concrete because the chemical is too big to fit in the pours. It will kill any mold on the surface but leave mold growing on the inside to start growing again as soon as conditions are right. To use on a hard, non-porous, surface, mix 1 part bleach to 10 parts water or 50% ammonia and 50% water. Never mix bleach and ammonia together. Put the solution in a spray bottle and spray onto the mold. Wait an hour and scrub off. Be sure to wear protective gloves and a respirator.
- Baking Soda - Baking soda is a mild house hold cleaner that will kill some species of mold. Mix 1 part baking soda into 5 parts water in a spray bottle. Shake to dissolve the baking soda and spray on the mold. Scrub the surface to remove the mold then rinse with water to remove any excess mold. Finally spray baking soda on the cleaned wall - baking soda removes moisture and will prevent more mold from growing.
- Borax - Borax is a natural cleaning product with no VOCs but is dangerous if swallowed. You can get Borax in the laundry aisle. Mix 1 cup of borax powder in 1 gal of water and scrub the solution onto the mold. You don't need to rinse off the excess solution, borax residue with actually prevent more mold from growing.
- Detergent - Detergent isn't capable of killing mold, but like ammonia and bleach, it can be used on hard, non-porous, surfaces to scrub mold off the surface.
- Hydrogen Peroxide - Hydrogen Peroxide will kill mold, fungus, viruses, and bacteria with no VOCs or toxic residue. Put 3% concentration hydrogen peroxide in a spray bottle and spray onto any moldy surface. After 10 minutes, scrub the surface until the mold is removed then wipe down the surface to remove any residue.
- Vinegar - Vinegar will kill most (but not all) species of mold and has no VOCs and non-toxic. Pour white distilled vinegar into a spray bottle undiluted. Spray the vinegar onto the mold and leave to sit for an hour. Wipe up the excess vinegar with water and allow to dry completely. The vinegar smell will dissipate in a few hours.
So obviously there are lots of choices. We originally went with the bleach solution, before researching to realize that this won't work on our basement walls, so now we'll be trying something different soon. We'll let you know what we find but in the meantime if you have similar mold problems, pick your poison and happy mold killing!