Divert Rain Water Away from Your Foun­da­tion with Under­ground Down­spout Extensions

Apr 28, 2015 • By Matthew Stock.

Base­ments can seep water through a num­ber of open­ings – non-struc­tur­al cracks in the wall, dete­ri­o­rat­ed mor­tar joints, cracks in the floor or the cove joint seep­age between wall and floor. 

The dam­age can be avert­ed and, in many cas­es, seep­age pre­vent­ed by divert­ing rain water away from the home’s foun­da­tion. Many home­own­ers think that just by clean­ing and main­tain­ing their gut­ters that they have done all they can to accom­plish this but they often ignore the end points of the gut­ter sys­tem – the downspouts.

Con­sid­er this – a one-inch rain­fall dumps 600 gal­lons of water on each 1,000 square feet of roof and that’s more than 1,000 gal­lons on the typ­i­cal home in the U.S. A clean and prop­er­ly pitched gut­ter sys­tem will col­lect all that water and pre­vent it from spilling over the edge of the roof and sat­u­rat­ing the soil around the foundation.

How­ev­er, if the down­spouts mere­ly ter­mi­nate a few inch­es above the ground, or dump water on a small splash block, all that water col­lect­ed by the gut­ters ends up next to the foun­da­tion any­way and in con­cen­trat­ed amounts in sev­er­al spots. Next stop? The basement.

Under­ground Down­spout Exten­sions Divert Water Away from the Foundation

The soil that sur­rounds a home’s foun­da­tion is par­tic­u­lar­ly vul­ner­a­ble to over-sat­u­ra­tion because of the long-last­ing effects of the exca­va­tion that was done when the foun­da­tion was built. The exca­va­tor dug what was essen­tial­ly a bowl in the ground and the foun­da­tion was built in the mid­dle of it. When the foun­da­tion was fin­ished, the edges of the bowl were back­filled and, despite the contractor’s best efforts to com­pact the soil, it remains more porous than the undis­turbed soil around it.

So, when exces­sive water lands in that ​“zone of fail­ure” (approx­i­mate­ly ten feet wide) it is like­ly to have a dele­te­ri­ous effect on the foundation.

This effect and the dam­age it can cause will be elim­i­nat­ed if the home­own­er diverts rain water away from the area by installing under­ground down­spout exten­sions. It is pos­si­ble to extend down­spouts above­ground but this prac­tice usu­al­ly results in inad­e­quate diver­sion, attach­ments that are knocked off by land­scap­ers or chil­dren play­ing or unsight­ly plas­tic tub­ing snaking all over the lawn.

Putting in under­ground down­spout exten­sions will ensure that the down­spouts dis­charge a prop­er dis­tance from the foun­da­tion and the exten­sions will remain undis­turbed regard­less of exter­nal con­di­tions or activ­i­ties. Water that would oth­er­wise end up next to the foun­da­tion (and then in the base­ment) will be car­ried far enough from the home to pre­vent it from caus­ing damage.

Instal­la­tion by a base­ment water­proof­ing pro­fes­sion­al will ensure that the down­spout exten­sions are equipped with a prop­er debris fil­ter, sloped to pre­vent back-ups and clogs and made with the right mate­ri­als. Also, a pro will make sure that the dis­charge of water is prop­er­ly man­aged, includ­ing tying the exten­sion into exist­ing storm sew­ers when local codes require.

Land­scap­ers, handy­men and oth­ers who aren’t experts in yard drainage but claim to be able to install under­ground down­spout exten­sions often use sub­stan­dard mate­ri­als and make dam­ag­ing errors in locat­ing the extensions.

At U.S. Water­proof­ing, we under­stand the impor­tance of man­ag­ing water out­side the home and have installed miles of under­ground down­spout exten­sion to help home­own­ers divert rain water from their foun­da­tions. Why not ask for our free advice about keep­ing your foun­da­tion (and your base­ment) dry?

Inter­est­ed in know­ing more about how under­ground down­spout exten­sions will divert rain water away from your foun­da­tion? Please post your ques­tions in the Com­ments box below.

Tags: divert rain water, underground downspout extensions

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