4 Steps to a Mold Free Home


Stop all water leaks and Keep the interior Relative Humidity under 52˚.

Outside humidity in San Francisco is normally around 50%.  In living and working spaces we find interior humidity to be between 40% and 52%. When the long term humidity exceeds 52% it becomes a concern. Humidity can be reduced by turning on the exhaust fans in the kitchen and bath, as well as opening the windows. Ventilation needs air coming and as well as air going out.

You can purchase an inexpensive humidity gauge from Amazon, Home Depot, etc. If you can measure it, you can control it. Everyone wins this way.

Water Leaks

If you see a leak try to stop it as soon as possible by turning of the water source, closing a window, or any other method appropriate. Then call your Property Manager or Landlord immediately. If it’s 4 am leave a message and follow up as soon as the office opens. 

The sooner professional drying begins the less likely that mold growth will occur. Everyone wins this way. 

The tenants are not displaced and have ruined contents; the landlord repairs the property much more quickly with less costs. 

Tenants may also wish to consider renters insurance. Be sure water damage is a covered loss.

NOTE: Notify building management as soon as possible. It’s much easier and faster to clean up wet contents than wet, moldy contents. Some, or all contents may be lost to mold.

If you suspect this is brown or dirty water spill, block off the area immediately and notify building management. Do not try to clean up this type of spill. Do stop the water source, if possible. Leave the area. Wait for professional evaluation.

Elevated Humidity

If moist air from your morning shower is exhausted immediately, mold is much less likely to grow in your bathroom and surrounding areas. To test the efficiency of your exhaust fans, turn the fan on. Then take one square of toilet paper and place it below the exhaust grate for the  fan. If the paper sticks to the grate, the fan is working properly. If not, contact your property manager or landlord.

No Insulation in Perimeter Walls Increases Humidity

San Francisco is an old City and insulation wasn’t considered necessary in the past. So, in an older building if you place your bed or sofa immediately next to a perimeter wall, you will probably see discoloration (mold growth) on the wall and adjacent furniture. To avoid this, keep all furniture a minimum of 6″ away from perimeter walls. Mold will grow on wood, too.  It is unrealistic to expect a landlord to tear down walls to insulated your apartment, so work together and keep your furniture 6″ away from perimeter walls.

Too Many People Living Increases Humidity

Rents in the City are high. I mitigate this situation, buy an expensive humidity meter and when the interior humidity reached 52 degrees, turn on the exhaust fans in the kitchen and bathrooms. Also, don’t overstuff closets. I know that’s a hard one, but you will be well served to rent a storage space for your extra contents rather than stuffing them in a closet.

Using communication among all occupants and management, you can have a healthy home for a long time!

The Importance of Routine Maintenance

Planning for routine maintenance will reduce water leaks and some causes of elevated humidity.

Inspect the heating or HVAC system’s filters. Don’t reuse filters, regardless of what the manufacturer claims. Here’s why: dust lodged in the fold of the HEPA filter. When you add water to wash some of the dust away, the inside fold isn’t clean and will retain a small about of moisture. Mold spores live on dust. Mold spores grow in the presence of water. So, you’ve got a filter that is growing mold that will infect the entire building when you turn on the system. 

Inspect all bathroom, kitchens and laundry plumbing for all plumbing. A non-penetrating moisture meter can become your best friend. If you find a leak at the base of a toilet then the wax ring has usually failed. This wax ring should be replaced during the next plumber’s routine visit.

Keep all gutters free of vegetation and leaks. Trim all overhanging trees a minimum of 18″ away from overhanging roof lines. Consider a barrier method to reduce vegetation build-up. Annually inspect the gutters for vegetation buildup and leaks.

Take a good look at all the grout. If you see breaks or missing grout, get a handyman to carefully replace the grout. If tiles need to be removed, and installed before 1981, then assume those tiles contain asbestos and lead. The asbestos will be in the leveling compound and adhesive. The lead will be in the sealer on the tiles. Assume or test. Be safe.

Make sure all windows and doors close completely without drafts. This will reduce interior VOCs and other dusts. Your HEPA air purifier will work much better with limited air exchanges.

Annually inspect the exterior for any signs of deterioration or water damage.

Every property has difference maintenance needs, so adjust this list to fit your needs.