Angie's How To Check for Mold

Date Published: Nov. 12, 2019

Time: 30 Minutes

Mold is a type of fungus that loves the moist, wet areas of your house. There are about 50 kinds of mold that are toxic to humans, plus it can cause serious damage to your house that is very expensive to repair ($10,000 or more). The best way to avoid a mold problem is to be proactive and inspect your house thoroughly at least once a year.

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Mold can crop up anywhere there's moisture, so bathrooms are common culprits. Check the area around your bathtub, shower stalls and shower pan very carefully – mold usually rears its head in the grout above and around the tub and shower because water can seep behind the tiles, where it gets trapped. Also check the area where your toilet meets the floor to make sure it's not leaking and providing a breeding ground for mold.


Every sink in your house is vulnerable to mold, so it's important to check all of them. Pay special attention to the areas near water pipes and valves underneath your sinks, which may have leaks. Use a flashlight to check dark areas so you don't miss anything!


Start by inspecting the corners of your basement, looking for mold or water leaks. Also check all closets and window wells. If your basement has carpet, touch all areas with your bare foot or hand to test for moisture. If you find any water, identify the source of the water immediately, fix the problem, and check those areas very carefully for signs of mold.


Note: If you have a finished basement, mold will be more difficult to detect because your walls and carpet may cover it up. Be extra vigilant with the smell test of your walls (step #5), and run a dehumidifier regularly to remove excess moisture.


Again, you're looking for signs of mold or water, particularly around the edges of the attic and in any closets or storage areas. Mold can also grow in attics due to inadequate air flow and high humidity. In that case, mold will grow on the underside of you roof deck (the plywood that the shingles are nailed to), so check that area as well. To prevent this problem, make sure none of your insulation is blocking the air flow to your attic. For more information about how to keep your attic in good shape, read: What to expect when inspecting your attic.


Mold can grow behind your walls where you won't be able to see it. However, the smell can give it away. Perform a nose check on the walls of your basement, bathroom, and any other room prone to moisture. If you detect that wet sock smell, contact a professional mold remover to take a closer look.


If you discover a relatively small and contained mold problem, you can usually take care of it yourself. There are many products you can use (bleach, vinegar, hydrogen peroxide) but tea tree oil is by far the most effective natural mold killer. It's more expensive than other options (about $10 for a 2 oz. bottle) but it is safer than many chemical-based alternatives. Mix 1 teaspoon of tea tree oil with 1 cup of water and spray the mold. The solution will kill the mold and prevent it from returning.

Related: How much does mold removal cost?


Note: If you discover a large mold problem or smell mold in your walls, it's time to call a professional to deal with the issue.


The best way to prevent mold is to repair any leaks or consistent sources of moisture throughout your house. Additionally, run your bath fan after taking a shower to remove damp air from the bathroom. If you don't have a bath fan, be sure to crack a window or leave the shower door open so moisture can escape. It's also a good idea to perform a bathroom caulk inspection to make sure you're all sealed up.