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Basement Finishing


Basement Finishing

The Owens Corning Basement Finishing System

Copyright Owens Corning
It's sometimes called the "forgotten space." It's sometimes called "the dungeon." And other times, it's just called "down there." It's your basement and it's a treasure trove, whether you know it or not.

No, you won't find hidden cash or hidden bodies, but you will find lots of potential living and play space. Finished basements run the gamut of uses. They can retain their same purpose as a storage/wash room, but with the surroundings tidied up and made more comfortable. They can become an extra bedroom or even an apartment for rent, if you need an extra source of income. Or, they might be transformed into ultra-swank playrooms for the adults (mancave, theater, bar, etc.) or for the kids.

What Does It Mean to "Finish" a Basement?

If you want to take it literally, it's a bit of a misnomer to "finish" a basement. Traditionally, basements were built as utilitarian storage places, not meant for finer activities. Basements too were built to benefit the house itself, by elevating the structure above possible flooding and to create a thermal barrier. So, in older homes, basement finishing entails creating a living space out of a space that was not meant for this purpose.

Yet in newer homes, basements can literally and purposely be left half-finished so that the owner has the option of finishing it if desired. It's a great cost-saving technique that allows you to shift some of the costs of building a home to a later time.

Your 3 Basement-Finishing Options

  1. DIY: The classic method of finishing your basement. You lay flooring, build walls, create windows, and run electrical wire by yourself. This work is done "from scratch," using common materials such as 2x4s, plywood, and flooring, rather than materials specially made for basement finishing.
  2. Contractor: The same as above, except you enjoy the luxury of someone else doing the work--for a price.
  3. Basement Finishing Systems: Basement systems are newest option. Companies such as Owens Corning that specialize in basement finishing use materials geared just for this. For example, instead of applying drywall as a wall covering, they may use wall panels made of a solid inorganic material to prevent rotting and mold.
Nobody ever said this was going to be easy. In fact, money or time may not be the reasons why previous homeowners never finished your basement. It could be one of these:

Concern #1: Ridding Basement of Moisture

Moisture, whether active flooding or high humidity, is the number one problem with finishing off a basement. If you can't control the moisture, you can't finish your basement. Ridding your basement of moisture can be frustrating, because water can come from many sources.

How To Overcome This:
In brief, steps to eliminating basement moisture are:

  1. Reduce exterior seepage by grading earth so it slopes away from the foundation wall.
  2. If you have cracks that run all the way through the wall, dig out earth down far enough so that you can fill the cracks with two coats of bonding cement.
  3. Install a sump pump inside the basement.
  4. Brush or roll on a masonry waterproofer to the inside of the foundation walls.
  5. Keep a dehumidifier running.

Concern #2: Basement-Specific Flooring

Your second concern is closely related to moisture: because basements may get wet, not just any type of flooring will work.

How To Overcome This:
The trick is to address not just the finish floor (the floor you see and walk on), but basement subfloor as well.

Subfloor: You won't be attaching your finish floor directly to concrete. Subfloor will both elevate your finish floor above moisture and provide a thermal break. A long-standing option for basements is to construct a subfloor of plywood atop 2x4 sleepers. Nowadays, you can buy 2' x 2' panels going under brand-names such as BARRICADE™ and Subflor that have closed cell polystyrene insulation and which lock together.

The Finish Floor: Just because you've constructed a nice subfloor doesn't mean you can lay down any kind of flooring on top. Aesthetic concerns aside, the best--as in most practical--type of basement flooring is hard and inorganic: ceramic or porcelain tile, sheet resilient flooring, concrete, or rubber roll. Second to that would be flooring that is affected by moisture but has some degree of recovery capability: engineered wood flooring, laminate, low pile carpet. Not recommended: solid hardwood.

Tip: Our resident flooring expert at About Flooring evaluates 9 types of basement flooring options.

Concern #3: Heating

Most likely, the basement has no heat source because no one anticipated anyone spending time down there.

How To Overcome This:
Before you start adding heat sources, insulate the basement from the inside with extruded foam plastic insulation. Suggested heat sources: add vents to your existing heating ductwork, thus diverting warm air into the basement (provided your furnace can handle the added space). Or add electric baseboard heaters which have the advantage of per-room, segregated heating.


Costs for basement finishing vary wildly. For a "lite" DIY basement finishing, you might be able to get by for under $15,000, using the most basic materials possible and subbing out none of the work. Basement finishing systems lock you into a tighter price range, from the mid $30,000s to the upper $50,000s. And contractor-driven basement jobs can go as high as you want, with jobs starting in the high $20,000s to low $30,000s.

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