How do I know if my subfloor has mold?

Author: Mr. Dino Shields  |  Last update: Saturday, July 19, 2025

Detecting Mold Growth Under Flooring:
  1. Visible Water Damage: Stains, discoloration, or warping on the flooring or nearby walls can indicate a moisture problem and potential mold growth underneath.
  2. Musty Odors: ...
  3. Allergic Reactions: ...
  4. Increased Humidity:

What does a moldy subfloor look like?

Subfloor mold often shows up as dark spots or patches under your floors. You might find it under carpets, vinyl, or laminate. The mold can look like black, green, or white marks on plywood or OSB, which are common in homes since the 1950s.

How to tell if there's mold under flooring?

Visible Signs

Look for: Discoloration: Patches of yellow, green, or black can signal mold growth. Warping: Uneven or bulging floorboards suggest moisture buildup, a breeding ground for mold.

Does moldy subfloor need to be replaced?

If the mold has penetrated deeply or the subfloor is significantly damaged, you might need to replace the affected sections. It's essential to ensure that the area is thoroughly dried and treated before laying down new flooring to prevent future mold issues.

What are signs of mold sickness?

Although symptoms can vary, the most common symptoms seen in people exposed to mold indoors include:
  • Nasal and sinus congestion.
  • Eye irritation, such as itchy, red, watery eyes.
  • Wheezing and difficulty breathing.
  • Cough.
  • Throat irritation.
  • Skin irritation, such as a rash.
  • Headache.

Early Stage Mould Inspection Tips from a Mold Inspector

How to test yourself for mold exposure?

There are several methods available to test for mold exposure:
  1. Blood Tests: Blood tests for mold exposure detect specific antibodies produced by the immune system in response to mold exposure. ...
  2. Skin Prick Tests: This method involves exposing the skin to small amounts of common molds to check for allergic reactions.

Can you clean up mold yourself?

Scrub mold off hard surfaces with detergent and water, and dry completely. Fix plumbing leaks and other water problems as soon as possible. Dry all items completely. Absorbent or porous materials, such as ceiling tiles and carpet, may have to be thrown away if they become moldy.

How much does it cost to replace mold on subfloor?

Subfloor Cost per Square Foot

Subfloor replacement typically costs about $3 to $10 per square foot. This range can vary based on labor costs, which will add $25 to $30 per hour, and the type of subflooring you choose.

Does home insurance cover mold?

Homeowners insurance doesn't usually cover mold damage or removal unless it's the result of a covered peril. If the mold in your residence was caused by something sudden or accidental, such as a bursting pipe or some other covered incident on your policy, you may be protected.

How to tell if a subfloor is bad?

Your floors shift or bounce when you walk on them.

If your floors begin to feel spongy, springy or bouncy, or if you notice the floorboards around you shifting when you walk on them, it could mean that it's time to replace your subfloor.

What kills mold under flooring?

Borax is highly recommended as a mold remediation product.

How do you know if you have black mold under your house?

Black mold tends to have a strong, musty smell, and of course, it displays a trademark black color. Mold must have a water source for growth, so any damp, humid areas of the home are often susceptible and places to search for large mold infestations. The real issue is that mold can hide in dark and small places.

How long does mold take to grow under flooring?

Given the proper conditions, mold will start to germinate and grow as early as 24 hours after encountering the moisture source. In 3 to 12 days, the mold spores will colonize. In 18-21 days, the mold can become visible. In general, the longer that moisture is present, the greater the chance for mold to grow and spread.

What is the best mold remover for subfloor?

Treat exposed molded subflooring with a mixture of 1 cup of borax and 1 gallon of water or an EPA-registered mold removal product. Spray the solution on the moldy subfloor. You can also soak affected subflooring with a brush broom. Wait 10 minutes, scrub the area, and repeat the process two more times.

How do you check for mold under the floor?

Detecting Mold Growth Under Flooring:
  1. Visible Water Damage: Stains, discoloration, or warping on the flooring or nearby walls can indicate a moisture problem and potential mold growth underneath.
  2. Musty Odors: ...
  3. Allergic Reactions: ...
  4. Increased Humidity:

What does a wet subfloor look like?

Signs may include loose flooring pieces or a floor that is undulating and uneven in areas. Wet or water-damaged subfloors that are structurally unstable can cause long-term problems with your home, and simply replacing the wood floor on top will not fix the problem.

How expensive is mold removal?

Most mold removal professionals charge around $10 to $25 per square foot. So, if you're removing mold from a 100-square-foot area, you can expect to pay around $1,000 to $2,500. But factors like where the growth is and the mold type can affect how much it costs to remove it.

How to test for mold in a house?

The two most common methods used to identify a mold problem are mold test kits or air testing sensors. These kits include the necessary air test devices, chemical strips, or Petri dishes and are available at department stores or online. They'll also come with an instruction manual for any brand-specific guidelines.

Will insurance pay to replace the entire floor?

Dwelling coverage, on your condo or homeowners policy, may pay to repair or replace your floors and carpet if they're damaged by a covered peril. For instance, if your home's floors are damaged in a fire, your home insurance may pay for new flooring, up to your policy's limits and minus your deductible.

Can a handyman fix mold?

Handyman can clean small areas of mold for you, set up dehumidifiers, and replace drywall that was removed during larger remediation cleanups. Want to have a professional help beat mold in your home?

Does my subfloor need to be replaced?

You Can Feel the Floors Move Beneath Your Feet

If your floor feels bouncy, springy, or spongy, that's a sign of a problem with your subfloor. As fun as a bouncy house is, if you're feeling a bit like you're in one on your wood floor, it's time for the subfloor to be replaced.

Does wood with mold need to be replaced?

If the wood has been wet or damp for less than 48 hours, it can generally be cleaned and disinfected of mold. But if it's been wet for longer than 48 hours or there's already a significant amount of visible mold growth present, then the wood should be removed and discarded using safe work practices.

What kills 100% of mold?

Hydrogen peroxide, commonly used to disinfect wounds, is active against a wide variety of micro-organisms including mold. It acts by releasing oxygen at a rapid rate, which kills mold by oxidizing the surface and breaking down proteins and DNA.

Should you call a professional to get rid of mold?

They have vast knowledge and experience in removing mold from homes and can track the source of moisture and fix the issue to stop excess moisture from building up in your home. You should also call a mold remediation specialist if you have tried to take care of the problem yourself, but mold keeps coming back.

Will mold just wipe off?

Mold, on the other hand, is alive and can reproduce. Unlike dust, simply wiping it away doesn't solve the problem; mold spores can linger and regrow.

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