Basement Walkouts

Basement walk-outs provide direct outdoor access to the basement and are common features in homes located in colder climates like Toronto, Oakville, and surroundings. However, unless the property is on a sloped lot, creating such an entrance requires the excavation of soil.

The walls of the stairwell act as retaining walls, and railings are necessary to ensure safety for individuals using the stairs. Additionally, to prevent accidents near the walkout, a guard should surround the opening. Implementing a drain at the bottom of the stairwell is crucial to avoid water accumulation. A raised threshold is essential to prevent water or snow from entering under the door when it is opened. 

While basement walk-outs might seem straightforward in theory, they are complex to construct, particularly when added after the house's original construction. These structures must withstand frost and lateral soil pressure. 


Professional experience and judgment are key to assessing their performance and identifying any necessary corrections. MMT Waterproofing Inc. will know how to navigate common issues!

Lowered Footings

During initial construction, the foundation and footing system can be designed to extend deeper in areas incorporating a basement walkout, to compensate for increased frost depth. 

This adjustment, while necessary, adds to the overall construction costs. Adding a basement walkout to an existing structure is a significant undertaking, particularly when it involves underpinning the foundation and footings near the walkout. 


A prevalent method to shield the walkout excavation from frost involves applying rigid insulation before constructing the walkout. This strategy, if executed correctly, helps to mitigate frost heave issues affecting the basement walkout and the adjacent house wall by slowing the frost's penetration into the soil.

Frost Protection

In freezing climates, it's crucial for basement walkouts to be equipped with sufficient frost protection. The creation of a basement walkout can lead to frost penetrating much deeper into the ground. 

In scenarios where the grade level next to the footing and foundation system is lowered by five feet to accommodate a walkout, frost can reach three or four feet below the stairwell's bottom. 


The potential for damage from frost heaving represents a substantial risk. Implementing effective surface water management, which encompasses proper surface drainage and the use of free-draining soils, is essential in mitigating this risk.

Pressure of the Soil

With retaining walls and basement walkouts, the foundation is subject to significant pressure from soil on one side of the structure. This pressure intensifies when the soil is moist, and even more so with soil that expands upon wetting. 


The combination of water expansion and soil swelling increases pressure further when these wet soils freeze. Additionally, the presence of frost and hydrostatic pressure in wet soil conditions can lead to heaving.

Heaving, Bowing & Cracks

Observing any signs of leaning, cracking, and bowing in the stairwell walls is crucial. The basement walkout walls need to be constructed as retaining walls to effectively counteract lateral soil pressure. 


Soil moisture, expansion, or freezing can significantly amplify the pressure on one side of the wall. The presence of more water in the soil results in increased hydrostatic pressure.

Soil Moisture

It's essential to monitor the drainage surrounding the stairwell, even in the absence of visible damage. The risk of frost damage increases significantly if the terrain slopes downwards towards the walkout. Soil cannot expand or freeze without moisture. 


The level of hydrostatic and frost pressure present depends on the soil's water content. Using granular backfill around the walkout is advantageous because it doesn't retain moisture.

Perimeter Drainage Tile System

Installing a basement walkout frequently disrupts the existing perimeter drainage tile system. The optimal solution is to extend and reroute this system around the basement, ensuring it reconnects at all endpoints. 


A clogged or malfunctioning perimeter drainage tile allows soil saturation around the walkout's base, which can lead to severe frost damage.

Drains Without Exterior Traps

Outdoor traps tend to freeze due to water accumulation; hence, drains located at the base of walkouts typically exclude traps. Instead, the walkout drain is directly linked to an interior floor drain pipe situated above its trap, effectively using the floor drain's trap. 


To prevent freezing, any necessary traps should be installed within the building's perimeter, ensuring they remain unaffected by cold temperatures.