BASEMENT UNDERPINNING


WHAT IS BASEMENT UNDERPINNING?

Basement underpinning is the process of removing soil below a crawlspace or concrete slab, excavating the area to create a lower support level and then adding new concrete footers, walls and floor to extend the depth or reinforce an unstable foundation.
This worthwhile home improvement requires professional expertise in foundation walls, excavation, footings and concrete floor replacement. We will do a careful evaluation of the foundation and surrounding area to determine job and building code requirements related to excavation depth, plumbing and electrical re-routing, and concrete work.

DESIGN STAGE

With the initial evaluation complete and your goals established, an engineer and architect will be brought in to design the new space. These experts will draw plans that detail moving and extending load-bearing walls required with this project. They will submit stamped drawings to the local municipality to obtain the necessary permits before work begins.

SITE PREPARATION

After plans are complete and permits issued, the site must be prepared for construction. Furnace connections must be re-routed to move all ductwork and equipment out of the way. The next phase requires technicians to install temporary supports or vertical jacks to hold the building in place while the underpinning is being done. Wooden boards or steel beams are used to disperse the weight of the structure and are removed once the project is complete.

LOWERING THE BASEMENT

There are several methods for completing the underpinning process, depending on the purpose for the project. The Traditional Mass method is used for shallow underpinning. In this instance, the soil underneath the foundation isn't strong enough to support the home. The weak soil is excavated and replaced with mass concrete. This provides both strength and a more efficient distribution of weight. The Beam and Base method utilizes the traditional mass base but also incorporates concrete beams. These are constructed underneath the concrete base to spread the load evenly for better support. A third method called Mini-piled underpinning allows the structure to rest on stable ground of 5 to 15 meters below the current footers. Piles are constructed and cased in steel. The 15 cm to 30 cm piles are driven into pre-drilled holes to rest on more stable ground.


The fourth and more aesthetic purpose for basement underpinning requires the existing concrete floor to be removed. The soil is excavated in sections, filled with concrete and small gaps are left between the old and new concrete. Non-shrink grout is used to fill the area in each section.

FINISHING THE JOB RIGHT

Regardless of which type of basement underpinning is done, once the process is completed, the old plumbing can be removed and new plumbing installed. Our experts will now install a waterproofing system to keep the area dry. A waterproofing membrane is added to prevent water infiltration from the outside. The exposed foundation walls are then backfilled. It's now time to waterproof the interior of the basement. An internal weeping tile system is placed around the entire perimeter of the room, below floor level. This drainage pipe will capture ground water and re-route it to a newly installed sump pump that will safely discharge outside. A layer of gravel covers the entire floor area and will provide a secure base for the new concrete floor.