Can a Basement Floor Be Lowered?

When you’re looking for ways to create additional living space in your Toronto-area home you may want to consider the option of lowering the basement. This basically means lowering the floor to give you a larger area with more head room. This is an ideal option if your current basement is hard to fit into due to its low ceiling. And with limited space and the red tape involved in adding a second story to a home in Toronto, lowering your basement floor and turning it into livable space is a great option.  The key is finding the right home remodeling company that has experience with underpinning.

Basement Lowering (Underpinning) project in Toronto home

How Basement Lowering Works

Basement lowering (also called underpinning) can be achieved by breaking up the existing concrete floor and then removing it. Once the floor has been removed the soil can be excavated to a lower depth. When you’ve reached the exposed foundation footings, the soil can be dug out to the depth of the new floor and footings and foundation walls can then be poured below the footing.

Basement Lowering-Underpinning Project in Toronto

When the extended foundation walls are in place an additional wall can be poured inside foundation’s perimeter which will overlap the top of the footings. This creates something known as a bench ledge and along with the knee wall it strengthens the structure and acts as a retaining wall for the outside soil. Once the extended walls have been completed the basement should be properly waterproofed, usually with interior drain tile, to help keep moisture at bay.

Crushed stone is placed and leveled out and is covered with a reinforcing grid and vapour barrier before the new floor is poured. Lowering your basement floor is an excellent way to make the room livable but it’s not something you can tackle without the aid of a qualified contractor who deals in foundations. The task requires special tools, engineering and construction methods as well as plenty of experience and know-how.

When lowering a basement you may also want to redesign the new space and add drains, a walkout, insulation and stud wall partitions etc at the same time. A building permit is typically required along with drawings from a structural engineer. The two common methods of lowering a basement are benching and underpinning with benching usually being the least expensive of the two. The underpinning method is more common when the homeowner wants to lower the basement floor by about a foot or more.

In some instances when the foundation walls are underpinned the process may disturb the stable soil which supports a neighbour’s footings. If this is the case underpinning may not be the best choice or the neighbouring foundations should also be underpinned at the same time. It’s also a good idea to make sure the new basement floor isn’t under the water table or close to it. The new underpinned wall should be approximately two feet above the water table.

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