The Perils and Pitfalls of Finishing a Basement

By MNR News posted 04-28-2021 12:10 AM


Basement RenovationsA finished basement can make your home more spacious, livable, and enjoyable. It can also add dollar-value for eventual resale. But before you start planning where to place your home movie theater and speak-easy style wet bar, there are four important things to consider. 

1. Remodeling is Riskier
 in Older Basements 

In most cases, basements built before the mid-1990s were not designed for use as living spaces. Generally, the foundations are not waterproof, and there is no vapor barrier beneath the concrete flooring. That creates high humidity levels and greater probability of flooding from snowmelt and rainstorms. This doesn’t mean finishing your basement is impossible, but you should definitely check your insurance before getting your project underway. 

2. Wet Soil Conditions 

A high-water table and poor drainage around the foundation can cause water to pool, and eventually push through openings in the concrete. Even if there are no cracks or holes, water can penetrate porous concrete and greatly elevate humidity. The effects of this more subtle intrusion can be seen in tell-tale white stains in the concrete. These are salt deposits left behind by evaporating water. The phenomenon is called efflorescence.  

3. Rainy Climate 

If you live in an area prone to big snow melt, soaking spring rains, or violent summer storms, you need to factor this into your plans. Inevitably, there will be a weather event that overwhelms systems to designed to prevent or mitigate water intrusion. 

4. Intended Use 

Are you looking for a casual “man cave” or a simple recreation area for the kids? Or do you envision a fully livable space with bedrooms, bathrooms, kitchen, and entertainment area? How you execute your remodel should be framed around the potential for water intrusion. In the words of Jeff Thorman, general contractor and host of Home Renovision on YouTube: “The best investment for a basement is one you can afford to lose.” 

Keeping Your Basement High and Dry

Fortunately, there are numerous ways to prevent or mitigate water intrusion. While none of these solutions can overcome poor construction or catastrophic flood events, they can help make a moderately damp basement into a space that’s comfortable and dry. 

Install a sump pump

Most modern basements have built-in sump pumps, but they can certainly be installed in older dwellings. To function optimally, the pump should be fitted in a basin beneath the concrete that is 18 inches in diameter and two feet deep. This will hold up to 20 gallons of water. Investing in a high-quality cast-iron model is well worth the cost because cheaper models are more likely to fail. Your pump should have a mechanical float switch that kicks it on when water rises and turns it off when levels fall. For areas with high water tables and heavy seasonal rains, a battery-operated backup pump is highly recommended. 

Invest in a high-quality d

If humidity levels in your basement regularly hit 50% and higher, a dehumidifier greatly improves the air quality and prevents the growth of mold, mildew and fungus. It can also prevent long-term rot and structural damage to flooring and framing.  


Simple floor-stand models are helpful in the short term but are not a permanent solution. To ensure optimal air quality in a humid basement, you’ll need a dehumidifying ventilator air exchanger installed in your HVAC system. These units automatically keep humidity levels between 30 to 50% and vent moist air out of your house. In tightly sealed newer homes, they also prevent the buildup of potentially noxious gases. 

Build a Subfloor

Whether you have an old basement never intended for habitation, or a modern one with a water-sealed, back-filled foundation, building a subfloor is an excellent way to manage the inevitable moisture intrusion.  


Constructed from wooden panels lined with dimpled, waterproof membranes, subflooring provides a vapor barrier that mixes air and water, helping it evaporate or channel to a drain. An insulated variety of subflooring also keeps the cold at bay, making the living space easier on bare feet. 


Ideally, any framing for walls should be constructed directly on top of the subfloor. That’s because any beams in direct contact with cement are vulnerable to moisture damage. 


Lastly, if you want wood floors in your new basement paradise, you’ll need to lay another layer of plywood on top of the subfloor. Otherwise, it won’t have the structural integrity required. 

Learn more about basement remodeling 

Obviously, there’s a lot more to consider when finishing your basement, from plumbing and electrical to aesthetics and design. Continue your education by reading these articles: 


The Pros and Cons of Finishing Your Unfinished Basement 


10 Things to Consider Before Finishing Your Basement 


How to Plan a Finished Basement 


Building a Dry Basement 


For a sobering look at the perils of finishing a basement, check out this video from Home Renovision: Thinking About Finishing Your Basement? Watch This First!