Basement Underpinning in Toronto: What’s Involved


Underpinning is a repair technique used to level out failing foundations. The process is used to make an existing foundation deeper for adding on to a building or to repair an uneven slab. Underpinning is done by four methods.

  • Mass Pour
  • Screw Piles and Brackets
  • Pile and Beam
  • Piled Raft

The Differences

Mass Pour Underpinning is done by digging under the slab and forming pits in the weak areas. Then the crew pours fresh concreate into the pits to shore up a falling or cracked foundation. The extra depth adds stability.

Screw Piles and Brackets is a method used to physically hold up the building. The crew screws large “helical” stakes into the ground next to the structure. Then they add a bracket to the top of the stake. Brackets clamp on to the side of the building and hold the walls up from the soil. This method is primarily used for foundations that are eroding underneath.

Pile and Beam refers to digging under the structure and installing a beam the length of the foundation. Fresh concreate is often added to keep the beam in place.

Piled Raft is used when digging isn’t an option. This method actually requires breaking the foundation and adding piles (rods) to the most burdened areas. Then the piles are connected together and fresh concreate is poured

Why Underpin?

Underpinning is necessary for old and crumbing foundations. The process is more efficient than starting from scratch. Many contractors use some form of underpinning in the construction process to ensure good structure durability.

The Pros

  • Underpinning is a good step to prolonging a structure’s life.
  • Cheaper than a complete rebuild (in most cases.)

The Cons

  • Not a Do-It-Yourself job.
  • An engineer should be involved from start to finish.
  • Improper work can lead to worse property damage.
  • Not a quick process.

What to Consider

  • Underpinning should only be done to a wall that holds the weight of the structure.
  • Do not underpin walls that aren’t holding the basic structure up, this will cause property damage.
  • Work from the outside-in.
  • Allow concreate 2 days to set.
  • Begin work at least 2 feet down and 3 feet across.
  • Always make sure the concreate is level and all cavities are filled.

All structures require maintenance. Underpinning will eventually have to done for any foundation. Understanding the underpinning process is the first step to ensuring your home or business stands for years to come. Remember to always call a professional for this kind of work. This is one job you don’t want botched.