Foundation Crack Repair
Prior to the mid 1970’s, most residential foundations were built using CMU (Concrete Masonry Unit) block commonly know as Cinder Block. Since then, solid poured concrete foundations have become the choice for most builders here in New England due to their superior strength, longevity, and cost. Cracking is the most common form of poured concrete failure and the repair options can vary depending upon symptoms, intended use, design strength, functionality and of course, cost.
What Causes The Cracks?
Foundation wall cracks occur in New England homes as a result of only a few causes. One is concrete shrinkage. Water is released into the air as concrete goes through the curing (hardening) process. If there is excessive water in the mix or this water is allow to escape to quickly, the concrete may shrink to a level which causes a crack. This is the least significant form of cracking as it relates to a foundation, and very common in concrete structures built today. Once the concrete is fully cured and has reached it’s maximum strength, shrinkage no longer occurs.
The second most common cause for a foundation crack stems from a excessive force being applied to the concrete. A force is some kind of pressure or load applied to the concrete which results in a failure like a crack. Some common forces large enough to cause this type of cracking may be a result of structure settlement, improper site drainage, premature site backfilling, or the use of expansive soils for backfilling. The source of this type of cracking is important to understand when it comes to properly choosing a repair method. The longevity of your repair depends on it. Other factors such as site/structure design, proper concrete mix design, and final concrete strength can also play into the ultimate cause of a crack, but tend to be less likely with today’s building practices.
Did You Know?
Most visible cracks found in residential basement walls extend all the way through the wall. This essentially means that your wall has broke into separate sections and is no longer a monolithic (without joints/seams) structure. This is not the intention of modern day foundation design and can lead to a higher risk for continual movement problems in your home.
Just because a crack doesn’t leak now, doesn’t mean it will never leak. If most cracks go through to the outside, they are all susceptible to water infiltration. The water now has a distinct path from exterior to interior. Not every rain storm will cause cracks to leak. Some may require specific less common events such as 100- year storms, wind-driven rain, quick snow melt with ground still frozen, clogged gutters or even a leaking or broken irrigation line.
Fixing a crack from the exterior is not the best way to insure success. Applying some waterproofing material over the crack from the outside does nothing fill the gap created by the crack. The wall is still 2 separate pieces and will act as a “hinge” at that location directing all future possibility of movement to that spot. Disruption of grade material and landscaping can be very expensive and sometimes not feasible due to porches, decks, pools, seasonal restrictions and utilities.
Interior pressure injection techniques offer many advantages over exterior methods. Access required is minimal even in finished basements. Different injection materials are used to fill the entire crack from inside face all the way to the exterior dirt side. Structural bonding properties of some injection materials offer permanent repairs with supplemental strengthening options available if needed.
Pressure injection is the process of injecting a liquid material into a crack found in a solid poured concrete structure. This process has been a primary method used in the repair, restoration and waterproofing of commercial and industrial structures for over 60 years. It is the preferred method of repair for many Civil/Structural Engineers involved in projects all over the world.
Depending on the type of material used, cracks can be waterproofed or even structurally repaired beyond its design strength, if needed. Since many concrete structures are used in below-grade (underground) applications, repair access can be very limited without cost-prohibitive excavation. Similar to residential foundations, this is exactly why pressure injection is a extremely cost effective method for basement crack repair. Exterior excavation is not needed in residential injection and interior access is all that is required.
Epoxy is an adhesive material used in bonding processes. It’s known for its tenacious ability to join two pieces together, many times, permanently. It’s strength properties are frequently higher than that of the materials being bonded. This is exactly why Epoxies are used in the structural repair of cracked concrete. When epoxy injection is done properly, it creates a solid monolithic piece of concrete re- establishing it’s designed strength. It is a rigid repair meaning it does not allow for additional movement at the repair site. If the cause of the crack is still present and its determined that structural movement is still possible, epoxy injection may not be all that is needed. See Fortress Stabilization
Polyurethane Grout Injection
Polyurethane grout is a chemical liquid used in the waterproofing industry for creating flexible barriers against water penetration, specifically cracks. It is commonly used on below ground infrastructures such as tunnels, dams, mine shafts and retaining walls. Grout injecting is a very versatile method and can be used in many residential sealing applications such as leaking cracks, pipe penetrations tie- rods, joint/seams and void filling. When injected, urethane grout reacts with water beginning a chemical foaming process creating internal pressures needed to drive the material into small/deep spaces creating a flexible waterproof repair. It is important to understand that Polyurethane offers no structural strengthening properties. It only acts as a gasket and offers no additional strength to the structure or repair area.