What Caus­es Foun­da­tions To Move?

Oct 31, 2016 • By Matthew Stock with Mike Likvan.

When your house foun­da­tion moves, it can cause every­thing from below ground seep­age prob­lems to cracks in the rooms above. That’s why foun­da­tion move­ment should not be ignored. The caus­es should be iden­ti­fied and addressed ear­ly, along with treat­ing the symp­toms. If this isn’t done, the move­ment can con­tin­ue and the symp­toms increase to the point where major, cost­ly recon­struc­tion will be necessary.

So what caus­es foun­da­tions to move? Beyond sin­gu­lar events like earth­quakes and con­struc­tion mishaps, there are gen­er­al­ly 3 major rea­sons – 1) the qual­i­ty of the foun­da­tions’ struc­ture, 2) the amount of water under­neath or next to them, and 3) the types or con­di­tion of soil sur­round­ing them. Let’s exam­ine each rea­son and dis­cuss what can be done to address them.

The 3 Rea­sons Caus­ing Foun­da­tions To Move

Con­struc­tion
For the past 200+ years area builders have used a vari­ety of mate­ri­als to cre­ate our homes’ foun­da­tions. The ones that are still stand­ing today are made of brick, block (cin­der, con­crete, ter­ra cot­ta), stone and porous poured con­crete. Except for the improve­ments made to poured con­crete over the years that has stopped it from being so porous, all the oth­ers mate­ri­als con­tin­ue to present struc­tur­al issues. This is because the non-poured foun­da­tions have mor­tar joints and are lit­tle more than mason­ry jig­saw puz­zles. Mor­tar joint foun­da­tions are made up of indi­vid­ual com­po­nents like puz­zle pieces that can move inde­pen­dent­ly when enough pres­sure is exert­ed on them by the ground mov­ing around them. Once pres­sure is great enough to crack the mor­tar joints addi­tion­al move­ment can eas­i­ly occur. To prop­er­ly and per­ma­nent­ly make any cracked foun­da­tion walls mono­lith­ic and sta­ble again typ­i­cal­ly requires struc­tur­al enhance­ments like steel braces, car­bon fiber and/​or piers installed by qual­i­fied pro­fes­sion­als with spe­cial­ized knowl­edge and exten­sive experience.

Water
Anoth­er fac­tor that con­tributes to foun­da­tions mov­ing in, down or up is too much water. Our neigh­bor­hoods typ­i­cal­ly get sat­u­rat­ed by rains and melt­ing snow through­out the year. When the clay soil sur­round­ing foun­da­tions gets over­sat­u­rat­ed it swells; caus­ing enough pres­sure to push foun­da­tion walls in. If the sat­u­ra­tion goes deep enough, the dirt beneath shal­low foun­da­tions (e.g. crawl spaces, gar­den apart­ments, garages and day­light base­ments) turns to mud. Foun­da­tions drop when rest­ing on mud. And when over­sat­u­rat­ed ground freezes, the expand­ing columns of crys­tal­lized water that form are pow­er­ful enough to heave foun­da­tion walls upward.

Not enough water also caus­es move­ment. When there is too lit­tle water because of extreme dry­ness and/​or mature veg­e­ta­tion suck­ing the mois­ture out of the earth, the ground cracks and the weight of the home com­press­es these cracks, caus­ing foun­da­tions to drop.

Being in an area of the Mid­west that reg­u­lar­ly expe­ri­ences extreme tem­per­a­tures and mois­ture, even rigid poured foun­da­tions aren’t immune to the result­ing ground move­ment. This is why water­proof­ing foun­da­tions in our area requires flex­i­ble fix­es like elas­tomer­ic mem­branes and polyurethane based repairs that can con­tin­ue to pro­vide a seal even in the face of our dirt swelling, sink­ing, heav­ing and crack­ing. It is also why foun­da­tion sta­bi­liza­tion requires engi­neered meth­ods that address these chal­lenges by reestab­lish­ing the walls struc­tur­al integri­ty and/​or anchor­ing them to sup­port­ive stra­tum lay­ers deep below the saturation.

Soil
This rea­son is equal­ly as sub­stan­tial as the first two because many of our neigh­bor­hoods orig­i­nal­ly start­ed out as swampy soil, and some were actu­al­ly part of Lake Michi­gan. In the late 1800s the Great Chica­go Fire forced the city to find a place to dis­pose of the con­struc­tion debris from that event. Much of it end­ed up in Lake Michi­gan. Today half of the neigh­bor­hood known as the Gold Coast and all of North Avenue Beach were once part of Lake Michi­gan before the fire.

Even­tu­al­ly cities allowed con­struc­tion com­pa­nies to build on top of filled in wet­lands. The prob­lem with build­ing on land­fill is its inher­ent prob­lems are hid­den, and often the fill is not suf­fi­cient­ly com­pressed leav­ing voids that encour­age soil set­tle­ment. Build­ing a city park on top of land­fill isn’t a big deal because the land needs to only sup­port the grass, walk­ing paths and occa­sion­al pedes­tri­ans or bik­ers who pass through the park. How­ev­er, when homes and apart­ments are built on land­fill, their weight com­press­es the ground caus­ing ongo­ing set­tle­ment issues.

Oth­er homes that aren’t built on land­fill are like­ly sur­round­ed by unsta­ble sand or expan­sive clay soil. Both of these soils present their own prob­lems. Sand is famous for not being a good sup­port for foun­da­tions. Clay is referred to as expan­sive soil because its min­er­als con­sid­er­ably swell when they absorb water and sig­nif­i­cant­ly shrink when they dry.

Under­stand­ing the mul­ti­tude of con­tribut­ing fac­tors when diag­nos­ing foun­da­tion prob­lems and design­ing effec­tive solu­tions takes sea­soned pro­fes­sion­als who have worked with the var­i­ous types of foun­da­tions and know how they are affect­ed by water and soil. U.S. Water­proof­ing was found­ed almost 60 years ago and has worked with hun­dreds of thou­sands of Mid­west foun­da­tions. That’s why it makes sense to give us a call when you’re look­ing for a foun­da­tion repair esti­mate.

Tags: structural foundation damage, foundation damage

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