How to Waterproof a Basement Before Finishing


How to Waterproof a Basement Before Finishing

A finished basement is the dream of many homeowners.  Sometimes it’s a necessity – a way to create badly needed living space for a growing family.  Other times it’s a luxury – a den, a family room, a playroom, a “man cave.”

No matter the intended end use for finished basement space, the job of turning raw belowground square footage into finished, livable, useful space is a big one.  Whether done by a professional or as a DIY project, remodeling a basement takes a lot of time, a lot of work and a lot of money.

Given this major investment in the project it is critical that the basement be in great condition before any work starts and that usually means that it is dry with no indications of seepage.  Nothing will ruin a beautiful remodeling job like soaked carpets, moldy drywall and damaged furniture so it is essential that a basement be fully waterproofed before any finishing work begins.

Of course, the homeowner could roll the dice and hope that seepage never occurs but, even though it is possible to fix basement water problems in a finished basement, the cost and aggravation factor will increase geometrically.

Waterproofing a Basement before Finishing

There are several ways that a basement can admit water and several methods of waterproofing one before finishing.  Some are specific to a poured concrete or masonry foundation; others apply to either.

Crack Seepage – A non-structural wall crack is the most common source of seepage in a poured concrete foundation.  These cracks can be repaired by injecting them with expanding polyurethane, which fills and seals the crack permanently all the way to the outside soil.  The polyurethane material remains flexible when it cures to prevent re-opening of the crack caused by minor foundation movement.

Cracks in masonry foundations occur in mortar joints and are best repaired by installing an exterior waterproofing membrane, a thick coating of asphalt-modified polyurethane that is troweled onto the outside wall.  Seepage from mortar joint cracks can also be managed by installing interior drain tile.

Cove Seepage – Another common source of seepage in any type of foundation is the joint between the foundation wall and basement floor, known as the “cove joint.”  Water enters the basement through the cove joint when hydrostatic pressure under the foundation forces it through.  Installing interior drain tile, a system of perforated pipe embedded in washed gravel under the basement floor, will alleviate this pressure, collect the water and carry it to a sump pump for discharge from the basement.

When installed properly, interior drain tile will be maintenance-free, making it an ideal preventative repair for a basement to be finished.

Wall Seepage – Both poured concrete and masonry foundations experience wall seepage: concrete through porous spots or over top of the foundation wall; masonry through the aforementioned mortar cracks and porous masonry like concrete block or brick.  Applying an exterior waterproofing membrane will solve these problems but the presence of extreme ground water will also require installation of exterior drain tile and heavy-duty drainage board to protect the membrane and channel water down to the drain tile.

Any homeowner who is planning a basement remodeling project will require the advice and assistance of an experienced basement waterproofing contractor to ensure that his or her dream basement won’t be torn apart in the future to repair water problems.  At U.S. Waterproofing, we’ve been keeping basements dry, finished and unfinished, around the Chicago area for more than 57 years and have more than 300,000 satisfied customers to our credit.  Why not ask for our free advice?

If you’d like to know more about how to waterproof a basement before finishing, please post your questions in the Comments box below.


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