Basement flooding is a common cause of mold problems in the basement. As a result, it is important for a homeowner to take immediate action in order to keep their home mold-free. Failure to do so can lead to a house-wide mold infestation in a matter of days or weeks.

After basement flooding, it usually takes a matter of hours for mold to start growing. It typically takes between 24 hours and 48 hours for one to see visible signs of such an infestation. This includes discoloration and the presence of a musty smell.

Here is what you should know about basement flooding and mold growth.

How long does it take for mold to grow in a flooded basement

Since mold can grow in a flooded basement within 24 hours after flooding, if you want to keep mold at bay, you need to ensure that you dry out the basement as soon as possible.

The following are tips that will come in handy in helping you to speed up the drying process. Taking advantage of these tips will help to prevent mold growth in your basement.

Tip 1: Opening up your home

The first thing that you should do is to improve air circulation in your home by opening up windows and doors. If your basement has a window or any other opening, keeping it open is advisable.

When you open up your home, you increase the rate at which moisture evaporates. This will speed up the drying process and thus make your work easier.

Tip 2: Removing soaked and wet items

If you have absorbent or porous materials, trying to restore them will be an unnecessary headache. Their presence in the basement will also make drying much harder. And they will also create mold-friendly conditions.

Therefore, if you have soaked papers, ceiling tiles, or cardboard, discarding them is advisable. And if any absorbent materials are still valuable, then removing them from the basement and airing them outside is advisable.

Tip 3: Use wet/dry vacuums or carpet extractors

Valuable carpeting that has been exposed to excessive moisture is a mold growth magnet. The problem is that sometimes, it is impossible to get it out of the basement.

In such a case, you need to hire a carpet extractor and use it to dry it out. A wet/dry vacuum also works wonders and can thus be used to speed up the drying process.

Tip 4: Cleaning surfaces with mold-killing solutions

Since some surfaces typically take a little bit longer to dry out, you should discourage mold from growing on them. And the best way to do so is to clean them with mold-killing solutions.

Spraying the surfaces with undistilled vinegar will work because vinegar kills about 80% of all mold species. Cleaning with baking soda or bleach will also work. And you can also use specialized commercial products that are specifically designed to prevent mold.

Tip 5: Install fans in your basement

Fans are great at improving the flow of air in a room. Therefore, they can come in handy in helping to prevent a mold problem.

Simply install one or two fans in your basement and turn them on. Having them running in the basement will enhance the air circulation in the space. This will in turn accelerate the moisture evaporation rate. It will thus speed up the drying process.

Tip 6: Use an appropriately sized dehumidifier

High humidity in the basement is a common cause of mold problems. Furthermore, things take longer to dry in highly humid conditions. And as a result, figuring out a way to lower the humidity in your basement is an easy way of preventing mold growth.

Humidifiers are the perfect devices to lower humidity. When you install a humidifier in your basement, it will easily reduce the moisture content in the air. This will in turn make your basement dry out faster, and this will discourage the growth of mold.

What are the first signs of mold growing?

When left unattended, mold can cause property damage. It can also trigger severe allergic reactions in loved ones. Therefore, getting rid of mold as soon as you notice it is always advisable.

The following are the signs that you should look for.


When mold grows on a surface, it discolors it.

Black, green, grey, white, or purple mold will tend to create ugly marks that resemble their color. Therefore, as soon as you notice such marks on your walls, floors, or any other items, you should definitely test for mold.

The easiest way to do so is to use bleach.

Simply pour bleach into a small container and then dilute it with water. Take a swab, dip it in the bleach and then dab it on the discolored surface.

if the discoloration fades, then you already have mold growth. And in such a case, swinging into immediate action by killing and removing the mold is always advisable.

A musty smell

Mold has a musty smell.

If you notice that your basement has this smell, then you likely have mold growth. And if the smell seems to be coming from your air conditioning system, then chances are that you have a house-wide mold problem that needs an expert’s immediate attention.

Allergic reactions in loved ones

When you have mold growing in your home, the concentration of mold in your home is bound to increase. This will then trigger allergic reactions like eye irritation, skin irritation, coughing, and having a running nose. These are thus a common sign of a developing mold problem.

Bubbling wall paint

Bubbling paint is a common sign of moisture infiltration. And since the presence of moisture on walls tends to be accompanied by mold growth, it tends to double up as a sign of a likely mold infestation.

Does water damage always cause mold?

Yes, water damage always causes mold. This is because mold spores already exist in the air and in most cases, all that these spores need is moisture. And when you consider the fact that most surfaces that can be damaged by water are mold-friendly, then water damage almost always leads to mold growth.

What kills mold after flood?

Mold killing solutions like vinegar, bleach, and commercial mold-killing sprays are great at killing mold after flooding. And drying out the flooded area before mold has a chance to develop is usually an effective way of preventing an infestation.

How many dehumidifiers do I need after a flood?

In most cases, you only need one dehumidifier after a flood.

One industrial dehumidifier is usually good enough to speed up the drying process in a large or medium-sized basement. While a good home and office dehumidifier can work if the basement is small. This is so especially if the basement isn’t crowded.

And in some cases, a specialized restoration dehumidifier is the only thing that can work.

However, if you have a large basement and you want to use a home dehumidifier, then using multiple dehumidifiers at the same time may be necessary. In such a case, you may even have to use up to 6 of these to have any effect on a sizable flooded basement.

On what humidity level does mold grow?

Mold thrives in conditions that feature humidity levels of 55% and above.

How to get rid of mold after a flood?

The best way to get rid of mold after a flood is to first fix the source of the flooding. Thereafter, getting rid of any materials with mold should follow. This should include any flooring or wall materials that have been severely damaged.

And after you are done, you have to then dry out the area by using a combination of vacuums, fans, dehumidifiers and improving overall air circulation in the area.

You should then follow this up by cleaning surfaces with mold killing solutions like bleach, vinegar, or borax. Thereafter, wipe the surfaces dry.

And if you don’t want to do it on your own, you can always call a mold remediation expert.

DIY vs. Hiring a Professional

Once your basement floods, you have the option of hiring mold remediation contractors. You can also choose to kill and remove the mold on your own.

Before deciding which option is suitable for you, it is always good to be aware of the pros and cons of each option.

Here is what you should know.

Do it Yourself


  • It is cheaper since you won’t be paying for labor or expertise
  • You have absolute control in terms of which cleaning chemicals or solutions to use
  • You get the work done at your own pace, convenience, and schedule


  • Higher risks of the mold coming back
  • It requires your total commitment in terms of time
  • It is tedious work

Hiring a Professional


  • Thorough cleaning and mold prevention that reduces the risks of a mold infestation
  • Gets the work done faster
  • No need for your commitment in terms of time or energy
  • No risk of exposure to toxic cleaning or mold removal solutions


  • It is more expensive
  • Less control in terms of what chemicals are being used in home


No, mold will not die if it dries out.

It will simply become inactive. And so as soon as it gets access to moisture, it will grow back.

No, painting over mold will not kill it. It will simply hide it from view. That is until the mold problem gets worse to a point where it can never be ignored.

A wet basement can take between a few hours to a few days to dry out. It all depends on the extent of flooding, how crowded it is, the air circulation in the space, and the steps that you take to speed up the drying process.

Homeowners typically spend between $3,000 to $10,000 on basement clean-up services. However, if the flooding is extensive, it can cost up to $25,000

It costs between $500 and $2000 to have a professional completely remove mold from your basement.

However, what you end up paying will depend on the extent of mold infestation, its location, the area’s size, and the mold type. Any after-remediation services that you need to be done will also affect the total cost of mold remediation services.

Yes, mold in the basement is dangerous because it can trigger severe allergic reactions. And for people with preexisting conditions, exposure can be fatal.

FAQ’s flooded basement

If you are looking for help dealing with a mold problem, the first place you should go to is It offers a free service that quickly matches you with the top-voted local mold remediation contractors.

Using the website, you can get 3 estimates fast by real certified experts in your area in just 2 minutes. Here is how it works.

  1. You scroll to the top of the page and enter your Zip code.
  2. Answer questions about your mold remediation needs
  3. Your details will be forwarded to three local experts.
  4. You will then receive a price estimate for the job and some friendly advice.

IMPORTANT: There is no obligation to hire. This is a free tool and service to be used at your pleasure.

Timothy Munene
Author: Timothy Munene - Timothy is a freelance writer and an online entrepreneur.