An entrance straight into the basement from the outside may be had in houses around cold climates. Except on sloped lots, creating this entrance does require soil excavation. Retaining walls are the walls of the stairwell and to protect people moving up and down the stairs a railing is needed. To protect passing by the walkout a guard should be provided around the opening and also to prevent the stairwell from filling up with water you can employ a drain at the bottom. A raised threshold to protect against water or snow from entering under the door should be fixed when opening the door. Basement walk-outs are tricky to build as much as they are simple to describe. They should be inspected with caution especially if added after original construction. Basement walk-outs have to resist frost and lateral sol pressure typically. To evaluate the performance and identify what should be corrected you must use your professional experience and judgment. Therefore in this article we will discuss some of the issues experienced with basement walk-outs.
To retain walls and basement walkouts soil on one side of the wall exerts considerable pressure against foundations. Additionally, soil that is wet exerts more pressure and even soil that expands when wet exerts even more pressure. The water expands and the soil exerts more pressure when wet soils freeze. Heaving can be caused with frost and hydrostatic pressure when the soil is wet.
Basement walkouts must have adequate frost protection in freezing climates. Where a basement is created frost penetrates deeper. The frost now goes three or four feet down below the bottom of the stairwell in an area where the grade level adjacent the footing and foundation system is dropped five feet by creating a basement walkout. It is a significant risk to experience damage due to frost heaving. To assist minimize this risk good surface water management which includes surface drainage and free draining soils is needed.
The foundation and footing system can be constructed lower in this part of the house to account for the greater frost depth which includes a basement walkout during the original construction adding up to the expense. It is a huge job to underpin the house foundation and footings in the vicinity of the walkout when adding a basement walkout to an existing house. To protect the walkout excavation from frost with rigid insulation before the walkout is constructed is a common approach in many areas. If conducted properly it will assist to prevent frost heaving issues to the basement walkout and the adjacent house wall and it also slows the rate of frost penetration into the soil. During inspections it will be difficult to know if a problem existed since cannot review the design but you can only evaluate the performance.
It is important to look for leaning, cracks and bowing in the walls of the stairwell. To withstand the lateral soil pressure the walls of the basement walkout must be built as retaining walls. The pressure exerted on one side of the wall by the soil can increase dramatically if the soil is wet, expansive or it freezes as previously discussed. The greater the hydrostatic pressure the more water there is in the soil.
Pay attention to drainage around the stairwell even where there is no obvious damage. The frost damage is potentially great if the ground sloped down toward the walkout. A soil will not expand or freeze if it does not contain any moisture. How much hydrostatic and frost pressure has developed is determined by the amount of water in the soil. A granular backfill is good if it does not hold moisture around the walkout.
During the installation of a basement walkout the perimeter drainage tile system is often compromised. Ideally, the perimeter drainage tile would be extended and rerouted around the basement and at all ends become reconnected again. Water is allowed to saturate the soil around the base of the walkout if there is clogging or failure of the perimeter drainage tile which has proven before to be serious frost destruction.
Water in outdoor traps would freeze in the water that is why drains at the base of walkouts usually do not have traps. An interior floor drain pipe above its trap is always connected from the walkout drain. Therefore, allowing the walkout drain to utilize the floor drain’s trap. There should be a trap inside the perimeter of the building where it is not susceptible to freezing in any case a trap is needed.
A French drain is where sometimes the drain discharges. The drain may discharge out through a hillside away from the building on a sloping lot. To keep animals out drain discharging to daylight should have grates. Drains can either be clogged or broken drains, missing drains or undersized drains. At the base of a walkout there should always be a drain unless there is a roof above or watertight cover.
We were thinking about extending our living space in Toronto downtown older home. These guys gave us a good option on getting more height in our basement and to finish it properly. Now we have extra bedroom and washroom that can be easily used for guests or as a rental unit.
Underpinnings.ca gave us awesome explanation of how excavation and lowering of the basement is done. They also included step by step video in the email with a quote. All these little details that the go above and beyond with just did it for us and without hesitation we started the permits and work. Such a great experience with all plumbing and waterproofing!
Our idea was to either do extension of the house on the side or do basement lowering. To our surprise home addition was much complicated and expensive. All quotes were at least double the price of what underpinnings.ca quoted us for giving us extra 2 feet of height and full basement finish. We recommend them to all Torontonians.