Basement Lowering & Underpinning

If you are looking for more livable space in your home, you naturally think of the basement. But what if you can’t stand up in your basement without bumping your head over your ceiling? MMT Waterproofing Inc. can help to gain headroom and lower or underpin your basement. 

The process of underpinning is very complex and involves a structural engineer. Our team will work accordingly with engineer drawings, dig down to the footing of your house and maximize the height of your ceilings, all while strengthening the base of your foundation walls. 


Basement lowering is no easy feat, but once done, it will expand your living space or even turn your basement into an income property that will pay for itself. And of course, it will incredibly increase the value of your house!

2 Types of Basement Lowering

1. Benching

The benching system, akin to underpinning, is designed to expand living areas by increasing ceiling height, albeit with a reduction in square footage. When finished in line with the benching method, it suits various uses. 

Offering a more budget-friendly and quicker alternative to underpinning, the benching system can achieve similar height enhancements in half the time.

Benching Process

1. Obtain engineer drawings and permits.
2. Remove the existing concrete floor.
3. Excavate the soil to its proper elevations. The height required will determine how far out from the wall the concrete needs to project. If you lower your basement 1ft down, then this means your concrete bench needs to be 1ft to 1 ½ ft out from the interior wall. 
4. Form the perimeter for benching once excavation is complete.
5. Install the new plumbing system; a sewer injector may be needed if specific elevation levels are unachievable.
6. Implement an interior drainage system to ensure waterproofing, laying at least 3 inches of ¾ inch gravel as the base.
7. Finish by installing a new concrete floor and smoothing it with a trowel.
   

2. Underpinning

The primary purpose of the underpinning system is to expand living areas by increasing the basement's height and overall square footage. 


Many homeowners opt for underpinning as it opens up opportunities to transform their basement into a rental unit, providing an additional income stream, or to create a fully finished basement, thereby enhancing their living space.

Underpinning Process

1. Obtain engineer drawings and permits.
2. Remove the concrete floor and excavate soil to the designated elevation.
3. Excavate pins in sections, following the engineer's plans, usually in three phases.
4. Install new footings for posts if required, using temporary jacks to support the beam.
5. After completing the first pin phase, fill the 2-inch gap between existing footings and concrete with non-shrinking grout.
6. Complete all three phases, then install new plumbing; if elevation requirements are unmet, a sewer injector is necessary.
7. Install interior drainage weeping tiles and a drainage board to waterproof the area.
8. Lay a minimum of 3 inches of ¾ gravel on the floor as a base.
9. Finish by installing a new concrete floor and smoothing it with a trowel.