Poured concrete is the only type of foundation that can be repaired by this method. 99 out of 100 poured concrete basements can be repaired quickly and inexpensively using injection. Here are 3 types of injection that can be done to repair poured concrete foundation: Crack Injection, Rod Hole Injection, and Tie Rod Injection.
Cracks are almost always visible “fractures” that tend to go from floor to ceiling and from the inside, right through to the outside. Cracks often originate from a point of weakness such as the corner of a window, a beam pocket, a utility penetration, or from the cut-out of a door sill. Occasionally cracks will form horizontally…this is more serious and indicates a structural failure.
Rod holes are created by the forming crew responsible for building your foundation wall. In order to hold the concrete forms together and to prevent bulging from the weight of wet concrete, 5/8″ rods are passed through the forms from one side to the other. After the concrete is poured, the forms are stripped off and the rods are removed leaving a 5/8″ hole passing right through your foundation wall. The holes are then patched with a dollop of hydraulic cement usually on the inside and the outside. But the middle is still one big air void!
Tie rod holes are similar to rod holes in that they too, are used during the building of your foundation wall to hold the forms together during the concrete pour and cure process. The difference is, tie rods are 1/4″ in diameter and they are left in the wall. Therefore they don’t leave a giant air void in your wall which is good. However tie rods are made of metal which is bad since metal corrodes in the presence of water and oxygen. As the metal corrodes, its mass decreases (ie.: it shrinks) and eventually leaves a void around the tie rod to allow water to pass through into your basement. To keep the metal tie rods dry, the builder usually applies a dollop of tar to the outside of each tie rod hole. The tar is not impervious to soil salts and therefore begins to break down within 3 to 5 years.
Crack injection is performed as follows:
- The crack is exposed, wire brushed, and cleaned with compressed air.
- surface ports are bonded to the wall over the crack using epoxy thixotropic paste. NO DRILLING FOR THIS PROCEDURE!
- the entire crack surface is covered with epoxy thixotropic paste, creating an inside dam to contain the liquid epoxy during injection.
- once the epoxy thixotropic paste has hardened the injection phase begins by injecting a 2 part low or mid viscosity epoxy (depending on the size of the crack) through the surface ports and into the actual body of the crack. The epoxy is usually injected from the bottom to the top. Since the dispertion of a liquid in a confined space is omni directional, we know that when the epoxy begins to flow from the next port up, that the entire crack below that point is filled, through to the exterior, and we can begin injecting the second port up from the floor.
- injection is continued from port to port from bottom to top. Crack
injection is complete when the epoxy begins to flow from the top of the crack. Crack injection is by far the least intrusive most effective method to repair a poured concrete foundation crack unless there are expensive basement finishing’s in the way of the repair. The epoxy injected into the crack actually repairs the crack by creating a structural weld within the concrete that restores the foundation wall back into a monolithic structure…..it also waterproofs the crack of course!
Limitations: Crack must not be flowing at the time of injection. Previous attempts at repair can disqualify you from this option, for example, if the crack has been gummed up with hydraulic cement or caulk, this repair can be difficult or impossible since we need to see the crack to inject it.
Parallel cracking: This occurs when a crack is injected with Epoxy and since the Epoxy is so strong, if the foundation moves, a new crack is formed immediately beside the crack that was just injected. We have injected 1000’s of cracks in the last 10 years and to date, we have not had one call back for parallel cracking. This may be because our epoxy has a slight flex factor to it or because this phenomenon is simply a myth. I believe it is the latter!
Alternatives: A Crack can be injected with polyurethane for less money
or if the crack never stops flowing and is constantly wet. The problem with
polyurethane in a small, hairline crack is that when polyurethane activates, it
creates air bubbles. In fact, most polyurethane expands to over 10 times their
original size! So when a hairline crack is injected with polyurethane, the net
result is a boat load of air bubbles and a small amount of polyurethane between
you and the great outdoors which may be fine for a large crack or rod hole, but
not for a standard foundation crack. 450 ml of Epoxy, when injected into a
wall, is still 450 ml of Epoxy after it cures!
Rod hole injection is performed as follows:
1st, a 1/2″ hole is drilled on an angle into the side of the rod hole.
2nd, a 3/8″ check ball packer port is hammered into the drilled hole.
3rd, polyurethane is pumped into the rod hole, through the check ball packer port until the entire hole is filled. This is the preffered method of rod hole repair since the size of the rod hole requires something that will swell and gel, by forming air bubbles, to fill the large space and seal it. To put this into perspective, a rod hole is 5/8″ in diameter and goes all the way through your wall to the exterior. Your garden hose is 5/8″ in diameter…..you get the picture.
Tie rod hole injection is performed as follows:
1st, a surface port is bonded to wall over the tie rod hole with epoxy thixotropic paste.
2nd, once the epoxy thixotropic paste hardens, the injection phase begins by injecting low viscosity epoxy through the surface port until the hole is filled and the entire rod inside the wall is coated and encapsulated with epoxy. This seals the void around the rod to prevent water from forcing its way through. Also, since the metal rod is not encapsulated in epoxy, further corrosion is now impossible.
A Crack can be excavated from the exterior and patched if it is not injectable or if exposing the crack on the inside is cost prohibitive.