Last Updated: Jul 10, 2021
Basements are a prime addition to many homes. Besides offering protection during intense storms and tornadoes, they are also a great way to maximize the amount of square footage for structures built on a small lot. From adding an enormous amount of storage space to finishing a basement as a rec room, indoor gym, or guest living area, over 30 percent of new single-family homes in the United States incorporate either a full or partial basement as part of their home design.
So what's the problem? Many basements, unfortunately, have that unpleasant "basement smell," which might be a strange combination of your great-grandmother's barn and a damp cave. The air quality in basements is widely considered to be the most compromised in a home and can affect the indoor air quality throughout your house. Improper sealing of concrete walls and slabs in the basement is one of the main culprits of that notorious smell that could negatively affect your health. If you're unclear about your indoor air quality, there are ways to measure it.
Basement floors and walls not sealed correctly will most likely have problems with humidity issues that will negatively affect indoor air quality. Finished basements with carpet and drywall will only exacerbate the humidity problems, as both carpet and drywall act like a sponge that holds moisture and allows mold to grow and reproduce. Mold in homes will release spores that can lead to severe allergies and increase the likelihood of household members developing asthma.
Radon gas can also negatively affect the indoor air quality through improperly built and sealed basements. Radon gas is a reaction from the natural decay of radioactive elements such as uranium, which can naturally exist in the rock and soil around your home. Since the air pressure inside your home is most likely stronger than the surrounding soil around your foundation, your basement will "suck up" the radon grass through even a minuscule crack in your foundation. In larger quantities, radon gas can lead to cancer.
Moisture, humidity, and certain gasses like radon gas only need a minimal amount of space to infiltrate a home. Most home contractors seal concrete slabs, the foundation, and all basement walls. These sealants fill up the "pores" that are naturally present in concrete, making it more difficult for moisture to enter. Many of the cracks in your foundation, slab, or basement walls result from excess water absorption by the concrete. As that water freezes and thaws, hairline cracks can form, thus affecting the performance of your basement.
A quality concrete sealer will help to protect your basement and home foundation from the moisture buildup that could potentially lead to cracks. Most concrete sealers, however, are made from solvents and other petroleum-based products that leach dangerous amounts of volatile organic compounds (VOCs) into the air. When applied inside homes, the VOCs released into the house only add to the compromised indoor air quality. Some of the most common solvent-based concrete sealants include chemical ingredients such as xylene, Napha-light aromatic, 1,2,4-trimethyl benzene, and cumene. Benzene is a suspected carcinogen, while xylene vapor is known to cause eye damage and deteriorate red blood cells.
The federal government restricts the VOCs in concrete sealers to 600 grams/liter. However, other states, such as California, limit the level to 100 grams/liter, effectively prohibiting solvent-based sealants all together. So what is another option? Water-based concrete sealants almost always offer the same protective benefits as their solvent-based counterparts. They also minimize the amount of VOCs and other toxic chemicals.
With water-based concrete sealants, the particles of polymers that protect your concrete from moisture-related damage disperse in a water solution that releases minimal VOCs. As the water dries and evaporates, the polymers move closer together before eventually fusing to form a continuous clear coating. The one drawback of water-based sealants is that this drying/evaporating process takes longer than petroleum or solvent-based sealants. However, water-based sealants will have very little odor and are also much easier to clean up after finishing the job. Below, Rise looks at three products on the market.
This water-based sealant has meager VOC ratings while still being able to penetrate and seal up several different types of surfaces, including concrete, rock, stone, grout, and concrete tile. It can protect for up to 15 years, which is several times more than other sealant products. Unlike other concrete sealant products, the Aqua Mix Sealer's Choice Gold is designed to cure in as little as four hours. You can purchase it through the Iowa-based Green Building Supply for $151.75 per gallon (at the time of publishing). Green Building Supply also offers its own brand waterborne concrete Penetrating Sealer for $55.99 per gallon.
Finding a concrete sealant that is zero VOC is not an easy task. Gulf Synthetics ConcreteRevive, however, is an entirely non-toxic water-based sealant that will protect and cover almost any concrete building material. ConcreteRevive can be mixed with colored paint to add color to your foundation or exposed basement walls instantly. This mixing ability allows you to combine two jobs into one. This product will leave zero odor once it has dried out and will dry to the touch within 10 minutes. If applying to a floor area, it should be safe to walk on it within a couple of hours. ConcreteRevive uses expand to a variety of concrete surfaces, including walkways, pool decks, driveways, garages, basements, concrete walls, stucco and brick exteriors, and more. It currently costs $240 for a five-gallon bucket.
TriCo Polymer also offers a VOC-free concrete sealer that is safe for use on basement interiors. Their Clear Satin ConKrete-Seal is non-toxic while still providing maximum moisture protection for your basement. You can use it for new or existing concrete floors, basement, and concrete block walls.
Conkrete-Seal is considered to be a flood-grade rated coating. It forms a robust, high adhesive micro-film that protects against mold, saltwater, and even pet urine. You can apply it on sub-floor concrete, under sill-plates. It also works well with green concrete, helping to cure by keeping the water level stable to prevent fast drying out that could lead to cracking. It currently costs $189 per 5-gallon bucket.
Note that each type of product's coverage of square feet per gallon will vary depending on the condition of the concrete surface as well as the application technique. If you are comparison-shopping for this product, make sure you understand the fine print, as the price per gallon may not be apples-to-apples in terms of coverage.
Basements are an essential part of millions of homes across the country. They are also one of the leading causes of bad indoor air quality inside our homes. Petroleum and solvent-based sealants can leach dangerous VOCs into our homes. Fortunately, any of the three water-based concrete sealants reviewed above are healthier alternatives that still offer superior performance.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.