Cracks: Epoxy or flexible polyurethane injection

To repair a crack embedded in the walls or foundations of your home, two products are very commonly used: flexible polyurethane and epoxy. During a repair, the technician either carries out their work with a flexible polyurethane injection or an epoxy injection into the crack to seal and waterproof the foundation.

What are the characteristics of epoxy and polyurethane?


The application of polyurethane meets very specific needs in the matter of waterproofing concrete cracks:

  • Very high flexibility to movements;
  • 100% suitable in the presence of water.


The application of epoxy provides exceptional resistance that is significantly superior to concrete when sealing structural cracks. This product is mainly used in large projects such as bridges, viaducts, multi-storey buildings, tunnels, dams, etc.

The presence of cracks in such constructions could weaken the concrete structure to the point of collapsing. Epoxy was also the first sealant to be placed on the market for this type of repair.

Should I use polyurethane or epoxy?

These are two very different products, due to their distinct and divergent physical properties: the capacity for elongation or flexibility.

As such, polyurethane-based injection liquids exhibit an elongation capacity of 10% to 400%, while the epoxy will provide only 0% to 1%.

In the residential sector, cracks have very little influence on the structural integrity of buildings. As a result, manufacturers routinely recommend the use of polyurethane for its elongation or flexibility properties in the case of active cracks or the possibility of movement.

Polyurethane provides an effective solution for waterproofing cracks in concrete. It therefore makes it possible to effectively prevent water infiltration. As for epoxy, it has a much higher resistance capacity, but will mainly be used for large structures (bridges, tunnels or dams, etc.). For a home’s foundation, Foundation Crack Expert Group recommends using polyurethane foam, which is both insulating and highly adhesive for crack repair.

Whatever the chosen treatment, it needs to be adapted to the type of material and the size and types of cracks present on your home. In any case, respecting the instructions for use of the product and the conditions of use is essential.

Epoxy and polyurethane application, the steps to follow

During a repair, our experienced technicians must first and foremost open and clean the crack to remove all dirt and loose particles.

Once this task is complete, the technician will proceed to implement the tools used for the application of polyurethane or epoxy. After this, the product will be inserted to seal your structural crack.

Next, the technician will place a reinforcement in the crack to prevent it from reappearing on the foundation.

The work will be completed after the drying period and the application of a new coating to flawlessly cover and finish the foundation.

At Foundation Crack Expert Group, we consider it necessary to inspect your cracks to ensure they don’t risk your structural integrity and proceed with repairs if necessary. Our experts will know which product to use to seal your cracks based on the situation.  Don’t hesitate to visit our contact page to get in touch with an experienced technician and benefit from our trusted expertise.