Using Polyurethane Injection for Fixing Cracks and Stopping Basement Leaks

Polyurethane injection (sometimes referred to as urethane injection) is arguably the most common type of injection used for repairing a basement leak and waterstopping generally, due to its versatility. It is used exclusively for stopping leaks in poured concrete foundation walls and structures. When leak repair / waterstopping is required in subway tunnels and mineshafts, the cracks and rock fissures are injected with polyurethane (also referred to as grout) - so you know this crack repair method works under real-life conditions. It should be noted that in some instances epoxy crack injection is a better choice to repair foundation cracks; particularly structural foundation cracks.

Click here for a comparison of epoxy and polyurethane injection methods for sealing cracks.

Polyurethane injection typically involves a high pressure (typically 1500-3200 psi) injection of activated polyurethane through injection packers hammered into drilled holes into poured concrete basement foundation walls. Like epoxy, the injected polyurethane resin travels through the entire thickness of the foundation wall (typically 8") thereby preventing water from leaking into your basement.

Note: Polyurethane can also be injected at a lower pressure using a process virtually identical to that used for epoxy crack injections.

 Installed Injection Packer  Polyurethane Crack Injection in Progress  Polyurethane Travels Through the Wall
Polyurethane injection packer fitting installed polyurethane_crack_injection_in_progress polyurethane-resin-expanding-through-a-foundation-wall-crack

How a high pressure polyurethane crack injection is done



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Polyurethane Injection Applications for Basement Leaks

  • Actively leaking cracks;
  • Cracks in wet or damp basement walls;
  • Previously repaired cracks (internally and/or externally) that are leaking; Note: an epoxy injection is not appropriate for use in repairing a failed crack injection;
  • Cracks full of mud or mineral deposits;
  • Cracks caused by corroding reinforcing bars (typically in reinforced concrete slabs);
  • Leaking forming tie-rod holes;
  • Leaking forming snap rods;
  • Leaking I-beam pockets;
  • Leaking underground structures in general (such as parking garage cracks and seams);
  • Underground pipe penetrations in a wall to accommodate electrical conduits, gas lines, air conditioning lines and pipes;
  • Expansion joints;
  • Honeycombing;
  • Pool bottoms (when access is possible);
  • Seams created by a cold pour;
  • Overhead concrete structures; and
  • Gaps beneath the window frame and the top of the concrete wall cut-out.

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 Images of Typical Polyurethane Injection Repairs

Actively leaking crack

Actively Leaking Crack

Failed crack injection

Previously Repaired Crack

Previously repaired crack

Previously Repaired Crack 2

Large foundation crack

Large Crack

Crack with mud and mineral deposits

Crack with mud minerals

Leaking forming tie-rod holes

Tie-rod holes with evidence of leakage due to visible sediment. 100 tie-rod holes were found to have leaked in this basement

Leaking tie-rod hole

Actively leaking tie-rod hole

Corroded snap rod

The rust stains beneath the snap rod provide evidence that water has leaked

Leakage through i-beam pocket

Staining beneath I-beam pocket provides evidence of water ingress. Injection packers are installed in preparation for polyurethane injection

Leaking pipe penetration

Electrical conduit entering through an oversized hole in the wall. Typically located behind the electrical panel, this situation allows the rapid entry of significant amounts of water into the basement

Leakage through honeycombing

Honeycombing - due to poorly mixed concrete or insufficient vibration after being poured into the forms. Water enters the basement due to the porosity of the concrete

Pool bottom waterproofing

Pool Bottom Waterproofing

Pourous poured concrete

Polyurethane expanding through concrete due to porosity

The Attributes of Polyurethane (PU) Resin

From reviewing the typical applications above, it is clear that polyurethane injection is an extremely versatile waterproofing method that can be used to deal with any basement leak in a poured concrete structure, under all conditions. This versatility is attributable to the characteristics of our polyurethane resins which are:

  • Our activated polyurethane typically expands to 2.5 times it's volume; this is very desirable when filling large cavities or when the size of a cavity is unknown (as in the case of honeycombing);
  • The expansive force of polyurethane is significant; consequently, it will fill any and all gaps that it encounters - this is particularly useful when dealing with very porous concrete or when dealing with honeycombing. It will also expand wherever it can; following the path of least resistance, it will fill any and all voids encountered;
  • Our polyurethane resins are non-toxic. This makes them suitable for use with potable water systems such as cisterns;
  • Polyurethane sets rapidly in the presence of hydrogen. Since hydrogen molecules are a component of water (H2O), the presence of water during an injection actually increases the reactivity of the polyurethane. This makes polyurethane the ideal product to use when active basement leaks and/or significant hydrostatic pressure, are encountered;
  • The polyurethane resins that we use will not freeze and always remain flexible (not an attribute of all polyurethanes); this is desirable when the concrete surrounding it expands and contracts due to thermal cycling;
  • Polyurethane sets very quickly. This is essential in stopping leaks where significant hydrostatic pressure is present;
  • Polyurethane injections are conducted using hydraulic hoses which are crucial when accessibility to the repair area is limited; and
  • At AquaGuard Injection & Waterproofing® we use polyurethane resins of varying viscosities; this gives us the ability to deal with any underground leak situation, from hairline cracks to large voids.

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Note 1: Several technical factors need to be taken into account to determine whether a basement leak should be injected using epoxy or polyurethane; for example, the effects of tension and compression at the crack location must be factored into the decision on how best to deal with your leak repair. Their is alot of science behind injection repairs; trust our trained technicians to determine whether polyurethane injection is optimal for your circumstances.

Note 2: Not all Waterproofing Contractors offer polyurethane injection basement leak waterproofing repairs. Why? Because it takes training, skill, knowledge, high quality polyurethane formulations, professional injection equipment and determination to perform a successful polyurethane injection; otherwise the injection will likely fail. As significant training and a commitment to work excellence is crucial, many companies shy away from polyurethane injections because they cannot reliably produce successful results. The demanding nature of polyurethane injection is so significant that some of our competitors call upon us to perform their warranty repairs!

Want more information on how foundation cracks are injected? Check out our blog post on polyurethane crack injection.

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