Do Basement Walls Need To Breathe?

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Sometimes, when moisture turns into a mold or mildew issue, you may hear someone comment that “the walls couldn’t breathe.” It’s a strange saying–breathe? But once you understand, it actually paints a vivid, accurate picture.

When walls can breathe, it means that moisture, such as humidity, can pass in and out of the walls without becoming trapped. Trapped moisture causes rot, mold, and mildew. Moisture needs to go in and out, just like air in our lungs.

So how can we facilitate that, avoid moisture issues in a naturally damp basement, and keep things dry and healthy? Keep reading to learn all you need to know about the issue.

A modern basement with cream colored walls, wooden cabinets, and a brown sleeper couch, Do Basement Walls Need To Breathe?

Why Walls Should Breathe

There’s plenty of advice out there on how to keep moisture out of your basement. You could read for endless hours – french drains, better gutters, landscaping, and sealing, all designed to keep moisture from your home and, by relation, your basement.

But the reality is that moisture will always exist, in some form or other, in the basement of a modern home. There is water in the ground (no amount of landscaping will stop it all), condensation, humidity, and moisture from the stove or shower – denying the water vapor that surrounds us all day is a fool’s errand.

Foundation walls like concrete are porous. This means they can take in 10-15 gallons of water vapor a day. The main difference is that back in the ’60s, homes were so drafty that moisture did not have long to stay and cause damage. It literally would dry up simply because of all the ventilation in the home.

Nowadays, houses are sealed up tight as a drum. It’s great for energy efficiency and your heating bill. But it’s bad for any moisture hiding in your home that can’t find its way out. That is why your walls need to breathe. Moisture needs somewhere to go, and a house that is sealed up too tight ends up with moisture in puddles and rotten drywall.

The Problem With Moisture

Moisture in a basement causes a number of problems, including:

  • Damage to any items stored in the basement, from actual water-damage to mold or mildew.
  • Damage to any construction materials such as drywall, insulation, or lumber, which will rot and mildew once wet.
  • Health hazards like mold and dust mites.
  • Pests like spiders, mice, ants, and cockroaches can be attracted to a basement with water issues.
  • Bacteria, which thrive in damp environments.

A cracked cement hollow block wall with algae growing on it due to moisture

How To Keep Outside Water Out

If you have major leaking, puddling, or pooling of water, the first step is to find the source and keep outside water in the yard where it belongs. No amount of “breathing walls” can keep a basement dry if it is being flooded by groundwater on a regular basis.

Solutions include:

  • Fix or lengthen downspouts so that water is redirected away from the house.
  • Slope landscaping so that water runs downhill and away from the foundation.
  • Install a french drain system.
  • Plug any cracks where water is entering.
  • Seal basement walls.
  • Consider an interior drain, which is built in the basement. Any water that does manage to enter through the wall is diverted into this drain system. A wall can be built in front of the drain to disguise the appearance, particularly useful in a finished basement.
  • Install a sump pump.

How Do You Prevent Mold On Concrete Basement Walls?

Mold will reoccur as long as there is enough moisture to support its growth. Once outside moisture is eliminated, it may be enough to fix any mold problems.

If the mold is due to moisture, such as humidity or condensation, you will want a hygrometer. It monitors the basement humidity.

Click here to see the ThermoPro Digital Hygrometer Room Thermometer and Humidity Gauge on Amazon.

Humidity levels in a basement should be kept around 50% (as a range, no less than 30%, and no more than 60%). If you see mold, chances are you are out of this ideal range. After reading your current level, you will want to first lower the humidity. The number of steps you need to take will depend on just how much of a correction you need to make. Some ways this can be done include:

Ventilation

Lowering humidity levels requires a process technically called mechanical ventilation. This means you must draw in fresh outside air while removing basement air outside. Simply circulating the same air with a fan will not reduce humidity. You can open windows, place fans in open windows, or install an exhaust fan that ventilates through a pipe to the outside.

Increased Basement Temperature

Air that is a warmer temperature can hold more moisture, which means a lower relative humidity. The more moisture that the air can contain, the longer time you have for that moisture to dissipate on its own without negative consequences.

Insulate Pipes

Pipes sweat, which adds moisture to the air and increases humidity. Insulating with a foam insulator like this one can get rid of that problem.

Click here to see 2 in x 6 ft polyethylene pipe insulation at Amazon.

Sealing And Insulating Ductwork

Sealing ductwork with mastic tape can prevent unconditioned air from blowing out from leaks and holes in the ducts and into the basement. Make sure to pick one that is water-resistant like this Hardcast Foil-Grip Mastic Duct Sealant.

Click here to see this product on Amazon.

Once leaks are solved, you will want to insulate with a product like Reflectix Spiral Duct Wrap. Sweaty ducts release moisture, increasing humidity levels.

Click here to see this product on Amazon.

Dehumidifier

You should take measures to address humidity issues in the ways previously suggested, before adding a dehumidifier. While a dehumidifier is very useful to control the humidity of a basement, it also uses electricity – which means it costs more to run more. By lowering the humidity as much as possible before implementing this last step, you can save yourself some money.

Be sure to select one that is made for basement use. Also, consider a model that has an auto-drain feature. This will allow you to simply drain directly into a sump pump basin without having to remember to keep draining the tank yourself. This one by Waykar will work on spaces up to 2,000 square feet.

Click here to see this product on Amazon.

Do You Need To Seal Your Basement Walls Before Finishing?

Sealing basement walls is always useful, but it is important to remember that sealing is only a small step toward a dry basement. Sealing is really only a solution to keep your basement dry from the occasional seepage that will eventually occur.

No one wants to see their finished basement ruined by one random incident from an unusually high water table. But you shouldn’t be relying on a sealed basement to keep all moisture out. You will still need to control water factors caused both from the outside and humidity inside.

Should You Use Drylock On Basement Walls?

If you only experience occasional seepage or dampness, Drylok is an appropriate solution. The waterproofing, antimicrobial and antifungal properties make it a good fit for a basement. The tints available allow you to paint in a color that you like.

Click here to see this product on Amazon.

Do Concrete Basement Walls Need Insulation?

Concrete basement walls are durable and hardy, but they aren’t a replacement for insulation. In fact, they perform rather poorly at that particular job. You can save as much as $450 a year by insulating with foam. If you live in climate zone 3 or higher, you should insulate.

If you have a significant water problem in your basement, you will need to address that first. Insulation becomes ineffective once it is damaged by water.

Once your basement is fairly water-tight, insulation will help prevent moisture caused by condensation. It creates a thermal barrier between the warm inside air and the cold outside air.

Avoid the use of fiberglass insulation. Fiberglass absorbs moisture (and, remember, moisture always exists in a basement, even if you don’t see it). This leads to mold. The best solution for a basement is rigid foam board insulation. Foam board must be installed with a thermal barrier cover, such as 1/2-inch gypsum drywall.

Do You Need A Vapor Barrier In Your Walls?

A vapor barrier, or vapor retarder, is meant to slow the passage of water vapor through the cement wall. In humid climates in zones 1-3, you should not use a vapor barrier. In marine zone 4, and climate zones 5 and greater, a vapor barrier is recommended by the International Residential Code.

In Closing

The ability of basement walls to allow moisture to pass in and out of the basement, also referred to as breathing, is an important factor in stopping water and water-related damage. Moisture can be caused by external factors such as groundwater seepage and internal factors such as humidity and condensation. Once groundwater is controlled, proper use of insulation, vapor barriers, and basement wall sealant can help to keep your basement a dry, safe space.

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