Every­thing You Want to Know About Leaky Base­ment Walls and Floors

Mar 11, 2012 • By Matthew Stock with Ben Shachter.

Get­ting water into the base­ment is an unpleas­ant sit­u­a­tion for any­one, whether you have a fin­ished base­ment in your home or if it is an unfin­ished stor­age area. Heck, even seep­age in an iso­lat­ed fur­nace or mechan­i­cal room is unac­cept­able. And water­proof­ing is not a want — it is a need, so it makes sense that most home­own­ers pre­fer to take the most effec­tive, yet con­ser­v­a­tive approach to fix­ing the prob­lem. Part of the process for water­proof­ing a base­ment is diag­nos­ing where the leak is com­ing from. A qual­i­fied pro­fes­sion­al water­proofer will usu­al­ly need some input from the home­own­er to arrive at a solu­tion to your leaky base­ment walls and floors.

While there are a num­ber of ways water can enter into a base­ment, it real­ly boils down to these four ways:

1. Water pen­e­trat­ing through the foun­da­tion wall.

By far, the most com­mon way for water to enter the build­ing is lat­er­al­ly through the foun­da­tion wall. If a foun­da­tion wall is con­struct­ed of poured con­crete, the cul­prit is most like­ly one or more ver­ti­cal cracks. Near­ly all poured con­crete cracks at some point — just look the next time you are walk­ing on a con­crete side­walk or dri­ve­way. Water can seep through oth­er voids in the walls such as a tie rod, a pipe pen­e­tra­tion, exposed aggre­gate (hon­ey­comb) or spalled con­crete. Mason­ry foun­da­tions, on the oth­er hand, are porous by the nature of their con­struc­tion. There are voids in the foun­da­tion every­where! Seep­age can occur between the indi­vid­ual units of brick, stone or con­crete block through the mor­tar joints. There are lit­er­al­ly thou­sands of joints that are sus­cep­ti­ble to foun­da­tion wall seepage. 

2. Water leak­ing from above the foun­da­tion wall. 

One of the more dif­fi­cult foun­da­tion water­proof­ing seep­age prob­lems to diag­nose is ​“over the top” of the foun­da­tion wall, espe­cial­ly when the base­ment is fin­ished with dry­wall or pan­el­ing. When the top of the foun­da­tion is buried beneath the grade or land­scape, it may seem to be the obvi­ous con­clu­sion. How­ev­er, it is pos­si­ble that the source of the leak is from high­er than the dirt-line. Just ask Sir Isaac New­ton! Grav­i­ty will cause water from leaky win­dows, door frames and even roof leaks to find its way to the low­er base­ment lev­el. The most defin­i­tive way to deter­mine if the leak is actu­al­ly from below grade is to place a run­ning gar­den hose next to the wall on the dirt or paved sur­face. Make sure to let the water flow and pool nat­u­ral­ly; don’t let it direct­ly hit the foun­da­tion wall. Most seep­age from the top of the foun­da­tion can be recre­at­ed with­in 15 or 20 minutes.

3. Seep­age at the floor/​wall joint.

Seep­age can occur at the floor/​wall joint (aka: cove joint) from hydro­sta­t­ic pres­sure from beneath the floor or lat­er­al­ly through the key­way, which is the joint where the wall sits atop the foot­ing. True hydro­sta­t­ic pres­sure from beneath the struc­ture will usu­al­ly affect a wide­spread area, such as the entire length of a sin­gle wall, mul­ti­ple walls or the entire perime­ter of the base­ment. Water pen­e­tra­tion where the foun­da­tion wall rests atop the foot­ing is usu­al­ly more spo­radic or iso­lat­ed. Actu­al caus­es for this type of seep­age range from voids at the base of the foun­da­tion, cracks in the foot­ing or even per­sis­tent stand­ing water next to the house. One con­stant is that water will always seek the path of least resistance.

4. Seep­age through cracks in the floor slab.

This is one true symp­tom of hydro­sta­t­ic pres­sure or a high water table.  When a water table forms beneath your build­ing it tends to rise uni­form­ly, com­ing up at both the cove joint and through cracks in the floor. It is entire­ly pos­si­ble that the pres­sure beneath the floor is what caused it to crack in the first place! This phe­nom­e­non occurs when water seeps into the ground and has no place to go after the earth is over-sat­u­rat­ed. Now, if you have a work­ing drain tile sys­tem, the water has a place to drain to, which pre­vents a water table from form­ing beneath your foun­da­tion. The lack of a drain tile sys­tem or even a failed sump pump can have your base­ment in ruins after a severe rain.

Once it has been deter­mined how the leak hap­pened we can pre­scribe a solu­tion that has been effec­tive in thou­sands of homes. As the largest base­ment water­proof­ing com­pa­ny in the Mid­west, our knowl­edge and expe­ri­ence is unpar­al­leled. You have ques­tions? We have answers, and plen­ty of them! We love help­ing peo­ple solve the mys­tery of their wet basements!

Tags: foundation waterproofing, basement waterproofing facts, most common problems

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