4 Reasons Why Foundation Walls Crack

All Structural Problems are caused by water. Get rid of the water, get rid of the problem.

J. Cochren, P. Eng.

Unreinforced concrete or masonry foundation walls have tremendous strength vertically but very limited resistance to lateral pressure. Most residential foundation wall are designed empirically - thickness of the wall versus the height of dry backfill.

If the adjacent soil becomes saturated, the lateral pressure against the foundation wall is increased by 15% sometimes, enough to nudge it inward and creating a crack.

If the water remains in the soil during a cold winter, frost will take hold and expand with 10 times the allowable pressure causing cracks for sure.

Four reasons the soil around the home becomes saturated.

  1. A clogged perimeter foundation drainage tile.
  2. The grading is level or slopes back toward the house
  3. Rain water leaders are not extended out from foundation
  4. Broken underground sprinkler systems or water mains

If the home is nearby a creek or storm ditches, occasionally overland flooding can quickly saturate the soils around the home to causing structural problems.

4 reasons why basement walls crack
Allow height of backfill of basement wall

Why Epoxy or Urethane crack injections do not always work in concrete foundations

Basement wall with crack injection
Basement wall with crack injection, no provision made to stabilize the wall from further movement.

Unreinforced concrete foundation walls over 40’will crack usually within the first 6 months due to shrinkage. Typical shrinkage cracks are consistent in width from 1/16” to 1/8” wide and usually a straight line vertically. The cause is self- explanatory.

For shrinkage cracks, urethane or epoxy crack injections are a very reliable solution to prevent ground water infiltration.

When an unreinforced concrete foundation wall cracks after the first year it is more likely as a result of lateral movement on the foundation wall or settlement. These cracks are y inconsistent width and not necessary vertical.

Unless the structural problem is identified and stabilize, the wall will most likely continue to move. Epoxy or Urethane crack injection will not work alone in this case.

Whenever there is a water problem it is important to look further to see if it is a structural problem before taking action.

Exterior Water Proofing

Water problems in basement are a health problem as well as a nuisance. Periodic flooding renders the basement unusable. Water cannot be controlled, just managed. Our approach is to waterproof the basement foundation from the positive side with a protective drainage board.

Exterior foundation waterproofing is the preferred method of waterproofing a basement foundation, preventing water from entering the basement from the exterior. The affected area of walls are excavated from the exterior, cleaned and prepared for waterproofing material.

EPRO waterproofing is applied to the foundation wall to provide vertical protection against nuisance water, perched water or ground water. EPRO will also protect against the lateral migration of various contaminated vapors and methane gas. A protection and drainage board is applied over EBRO providing a secondary line of defense.

Exterior waterproofing detail

Drainage is more important than Waterproofing

Weeping tiles are typically clay tile or plastic pipe that extends around the base of the foundation footing to collect any water that accumulates. The weeping tile is connected to either a sewer or a sump pit. Today most new homes have sump pits and pumps.

After installing the waterproofing and protection board, the weeping tile should be inspected and checked to ensure the system is functioning. Water needs a place to drain to.  Without a place to drain to, rising or descending ground water will find alternate ways to get onto your basement floor.   Drainage is more important than waterproofing.

 If the weeping tiles are not functioning, there are two options.

An attempt to flush out the remaining buried weeping is often successive by flushing out the system with high pressure water up to 4,000 psi  

If the weeping tile cannot be flushed out, the remaining option is to install a sump pit and pump on the interior.   A section of weeping tile is installed along that section of foundation wall being repaired and connected into the new sump pit.

Foundation drainage and waterproofing

Waterproof Stone Rubble Foundation

Stone rubble foundations are typically 18” to 21” wide without a footing. Often referred to as gravity wall - without engineering properties. Lime mortar used in the construction of these walls allows for movement an important design detail when rebuilding.

If the wall was in an area with poor drainage, chances are that the lime has been washed out mortar bed leaving the very vulnerable with only sand between the stone rubble. The condition of the foundation wall needs to carefully investigated before attempting to waterproof.

The weeping tile must be installed approximately 12” below the base of the stone rubble wall to prevent ground water infiltration below the wall. The excavation should be at a slope of 2:1 away from the bottom to prevent undermining the structure.

Waterproof stone rubble foundation

Interior Water Control

Often due to budget or physical constraints eliminate the option for exterior waterproofing. Interior water control if done properly provides a viable option for controlling ground water infiltration at about ½ the cost. This system is not recommended for use on Stone Rubble foundations.

The ground water is allowed to migrate through the foundation wall and by gravity falls to down behind the drainage board to the top of the footing. This water is collected by a 3” perimeter diameter drainage tile that discharges into a sump pit.

The key in this system is to seal all edges of the drainage board to prevent moisture escaping contaminating the indoor air quality.

Interior waterproofing detail

Moisture Control in basement

It is important to keep the humidity in your basement below 45% relative humidity. While this may be possible in the winter with the furnace running, it is not so easy in the summer. Unless you have a means to control moisture, you may be fighting a losing battle against mold and mildew in your home.

Sump pit and pump

A typical 1/3 horse power sump pump is sufficient to deal with ground water in most homes. These pumps have the capacity to discharge 2,400 us gallon per minute (GPM) with a hydraulic head of 10’-0”

A sump pump is useless without an alarm.

Equally important as the sump pump itself is the alarm to provide a simple audible alarm to let you know the sump pump is not working. Many of home owners have ventured into the basement surprised to find it is submerged simply because the sump pump failed – usually from a faulty float switch.

Sump pits should be perforated to allow accumulated water below the basement slab a place to drain, The 6” stone base below the concrete basement floor provides two functions. It provides a capillary break preventing water from wicking up from the earth below as well as a thermal break from the cold earth. If the voids in the stone are filled with water, both barriers are no longer effective.

Sump pit and pump foundation detail

Basement Foundation Waterproofing and Drainage - Service Area

We provide basement foundation waterproofing and drainage services in the .

Need Basement Foundation Waterproofing and Drainage Services?

Call us for an estimate: Hamilton: 519-647-0256 / Toronto: 647-921-7437.
Alternatively, you can submit your estimate request online.

Cochren Foundation and Repair Company is proudly affiliated with the following professional organizations in Ontario and Canada, dealing with quality assuring in construction and engineering projects.

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