House Smells Musty After Rain: Causes And Solutions

By: Jan Hajek | Date Posted: April 29, 2018

Different houses often have different smells which reflect the nature and lifestyle of their occupant. Sometimes, environmental factors such as the weather could exacerbate the issue and make the house atmosphere become unbearable. That is why your house could emit unpleasant odors during season change or after heavy rain.

In the usual case, there are many things that could make your house smell musty after rain along with a variety of solutions. If you are interested, this article will introduce you to several ways to deal with the odor in the short term and long term. There is also a detailed guide on how to get rid of other odors as well in case you run into them in the future.

What are the causes of the musty odor?

For most the time, if you don’t clean your house regularly and thoroughly, there would be a musty odor in the house atmosphere. Old furniture and aged construction material are also prime suspects behind that detestable stench in your lovely home. At first, the odor could be limited to a section but if you fail to come up with a solution, it would envelop the house.

Here are some of the most common culprits.

What are the causes of the musty odor?

Mold and mildew

Places that are constantly exposed to high humidity such as pipes, roofs, and alike tend to experience moisture built up over the years. Combined with low light and stagnant air, these locations are excellent breeding grounds for mold and mildew. In many cases, the funguses could grow in a completely undetectable manner because they are shielded by the house walls.

Long after the funguses are eliminated, the odor could still linger in the atmosphere because it has penetrated the house curtains, carpets, etc.

HVAC system

As time goes by, the efficiency of the house’s HVAC system will slowly but surely drop. After a number of years, these arrangements could become dusty, rusty, and smelly. Hence, the HVAC ductwork could circulate a musty odor around the house interior whenever you turn on the system.

Cigarette and Cigar

Drywalls often absorb odors that they are subjected to on a day-to-day basis which include the smoke of cigarettes and cigars. So if the house owner is a smoker, the musty odor could be retained and emitted by the house walls for years. In the usual case, smoked-absorbed walls would have noticeable brown or yellow nicotine stains on them.

Foods and drinks

If you don’t properly clean up spilled foods and drinks, they are going to resurface later on in the form of a nasty smell. Leftover snacks and fermented beverages could also generate a musty odor in case you don’t store them correctly. Similar to cigarette and cigar smoke, the kitchen walls would soak up cooking smoke and release an unpleasant smell into the atmosphere.

How to get rid of the musty smell?    

How to get rid of the musty smell?    

​​​​​​​​Temporary methods

An air freshener is able to mask the musty odor of the house when used due to its strong odor. Opening up all the windows and doors could provide a short-term boost to the house’s ventilation and push out the musty odor. However, these methods only work temporarily, it’s advised that you attempt to eliminate the source of the odor as soon as possible.

Permanent methods

Take care of moisture built up

Repair leaky pipes and cracked roofs in order to avoid moisture buildup, it’s often enough to prevent the growth of fungus. It’s also wise to seal exposed dirt floors using concrete so as to eliminate musty or earthy odors in hot humid weather. You could attempt to pour concrete over the area on your own or you could hire a contractor to do it for you.

Clean the air duct and update the HVAC system

During normal operation, ducts and like could accumulate inside the air duct and decrease the system efficiency by as much as 40 percent in some cases.  The build-up also permits the growth of microbial which could lead to the circulation of the musty odor. To clean the air duct, you must have suitable equipment and you should only do it when there is no in the house.

To reduce the number of time you have to clean the air duct, you should change the filter regularly and perform maintenance periodically. If the cleaning isn’t enough to solve your odor issue, the smell probably embedded itself in the component of the HVAC system. In that case, you have to consider replacing the entire HVAC system in order to get rid of the musty odor for good.

Swap out the carpet and curtain

Take a quick sniff of the fabric in order to decide whether the musty odor is coming from these items. Unless you just replaced them recently, swap out the carpet and curtain if you encounter a foul stench on them. The carpet comes in contact with people’s shoes regularly so make sure that you wash it regularly.

Inspect places with high humidity

Fungus often grows where it’s wet and damp so take a good look at places with high humidity such as the bathroom. In the case you spot mold and mildew, deal with them using an acidic compound like vinegar and so on. That should be enough to eliminate the musty odor once and for all, the smell would fade away from existence in no time.


Dehumidifiers and ionizers are excellent ways to keep the house atmosphere acceptable and free of moisture at any given time. You could also place a bowl of active charcoal at strategic locations across the house to absorb unpleasant smells and sanitize the air. Finally, it’s recommended to set up a logical cleaning scheme to make sure the odor will never visit your lovely house again.

The difference between musty and moldy odor

While the cause of the musty and moldy odor could be the same in some cases, they are not similar to each other.  Moldy odor tends to be the stronger one of the two and it indicates that without a timing response, the fungus could cause extensive structural damage. On the other hand, a musty odor only means that something is wrong and that you should take a look around the house.

Other common odor issues that you could run into

Other common odor issues that you could run into

The house smells like urine after the rain

In most cases, this is caused by a leak in the house facilities or an encapsulated crawl space. In certain situations, pet pee could get soaked up by hardwood and the pee would be squeezed out when there is a rise in humidity. Therefore, you have to deal with the leakage or tear the pee-soaked hardwood away to remove the urine smell.

The house smells like rotten eggs when it rains

This could be caused by a loose or punctured toilet gas ring which leaks methane gas into your house. All it takes is a pin-size gap or crack for the methane gas to flow into the house unopposed. Replace the ring and see if it’s enough to solve your odor issues.

Septic tank smells when it rains

After a heavy downpour, the air becomes heavy which makes it hard for the methane gas to dissipate through the vent. To solve it, run water through the house sink, bathroom, drain, and shower everyone in a while. While you are at it, pour down a couple of quarts of treatment compounds such as CCLS as well.

The house smells like sewage after rain

A punctured sewer pipe could be the cause of the nasty smell you are experiencing. It contaminated the soil right below the house and when the rainwater saturated the ground, the smell would resurface. The best solution is to wait for the ground to dry and then pour a couple of gallons of bleach around the house.

The basement smells like sewer when it rains

You most likely have a water trap somewhere that has dried out due to the lack of use. When the water evaporates, it allows sewer gas to pass through the drain into the room. Dumping a few gallons of water into the drain should fix your problem.

Another potential culprit would be the cleanout plug inside the drain, remove the drain cover and see if there is a plug there. If the plug is missing, the sewer gas could bypass the water trap and go straight into the room through here. Grab a replacement plug from the local hardware store, install it and you should be able to prevent further infiltration of sewer gas.

The yard smells like sewage after rain

There are two possible causes: clogged drain field and leaky sewer pipes. These make the septic tank sewage come up through the ground and release a horrible smell in the process. In most cases, you should contact a professional septic company and let them take over the repair. It’s unwise to attempt to deal with the situation on your own when you are inexperienced. Hire a professional handyman to work instead.


What absorbs smells in a room?

Baking soda, charcoal, and kitty litter are good items that absorb smell in a room. Place a bowl with one of these items near the smell’s source to get rid of it.

Why does my house smell musty after it rains?

There are many reasons why your house smells musty after it rains. Here are some of the most common culprits:
1. Mold and mildew in places with high humidity.
2. Old and dusty HVAC system.
3. Spilled drinks and food.
4. The smoke of cigarettes and cigars.

What are the signs of mold in your house?

1. Your HVAC system smells weird.
2. Your wallpapers are peeling.
3. You find dark spots on your walls.
4. You feel like you have a cold.
5. You feel itchy.

Does the mildew smell go away?

Yes, the mildew smell will go away after you find and eliminate the source of the unpleasant odor.

Thank you for reading!

Jan Hajek

I am an experienced writer. I write about home improvement topics such as construction, electrical work, plumbing, security and safety, interior design, exterior design, tools and woodworking, gardening, and garage organization. I love helping people improve their homes and make them more enjoyable places to live.

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