When building your dream home or cottage, most of the excitement is about what you’ll see; the cabinetry, flooring, and colours that bring it to life. But before any of that comes together, it’s the part you’ll never see, the foundation, that determines how well your home stands the test of time.
Foundations are like insurance. Nobody really spends much time thinking about them unless there’s a problem. However, just like insurance, most issues are resolved at the outset when you choose the policy, or in this case, the foundation type.
Just as you rely on your insurance broker to help you navigate your policy choices, you should rely on your builder to navigate the foundation choices. But what do you need to know to be confident you’re making the right decision?
The Three Most Common Foundation Types
These are the most common foundation types from a homeowner’s perspective.
Slab on grade. This is a flat concrete pad, typically with a thickened edge for reinforcement below ground that is not visible. These foundations are ideal for flat areas, where a basement isn’t needed, or where the water table is high and there’s a risk of water seepage if a basement is dug below grade. This is also a relatively cost-effective option for a foundation.
Crawl space. This is typically a four-foot-high concrete wall that allows plumbing and mechanical systems to be positioned below the main floor. This provides space savings on the main floor, as well as excellent access to any future plumbing or mechanical systems, not just in the event of an issue, but also for future development. You can upgrade your acrylic shower to a tile shower with a different drain location, or add an electrical outlet in your bedroom. Having access from the bottom makes any future changes or modifications much easier.
Full-height basement. This is typically an 8- to 10-foot concrete wall, dug at least halfway into the ground, possibly more. This type of foundation is ideal for development, especially if you have relatively large basement windows. It also makes for very cost-effective development, as you’re not adding any additional roof structure for this extra space.
What Lies Beneath Footings and Piles
Foundations number two and three from the list above are actually incomplete as described. Crawl space walls and full-height basement walls still require something underneath to support them.
Regardless of the height of the foundation wall, it will either sit on a footing or some type of pile. And it’s the footing or the piles that actually give the foundation its strength.
Choosing what the foundation wall should sit on is the most critical decision of a new build.
Footings. A footing is usually made from poured concrete and generally measures approximately 3 feet wide and 1 foot thick (sizing can vary based on the structure and soil type). A footing distributes the weight over a larger area, much like a snowshoe distributes a person’s weight in deep snow. This type of foundation can be highly effective in many different soil conditions and is very common in Manitoba.
Piles. Piles can come in several different forms:
- Poured concrete piles. These start by drilling a hole into the ground (usually 16” diameter and 20-25’ deep), then filling it with concrete. The friction between the concrete and the surrounding soil gives it its strength. These are excellent for Manitoba’s clay soil conditions.
- Driven piles. These piles are either precast concrete or timber and are pounded into the ground using a large machine. They’re ideal when ground conditions have a high water table or silty soil that could cause a drilled pile to collapse.
- Helical screw piles. Made of steel tubing with a helical plate at the bottom, these piles are screwed into the ground to the desired depth. The plate acts like a footing, displacing the load below grade. Screw piles are low-impact and often more cost-effective than driven piles, especially in soil conditions that make poured piles impractical.
How to Choose the Right Foundation
What’s described above accounts for about 95% of new foundations in Manitoba. But how does this help you decide what’s best for your project?
The first three types, Slab, Crawlspace, and Full-Height Basement are determined mainly by how you want to use your future space and what your long-term plans are.
What goes underneath those walls is determined by the soil conditions.
Choosing the right foundation type is often about choosing what won’t work. For example, in ground filled with boulders or solid rock not far below grade, like many cottage builds in the Whiteshell, a footing is often the only viable option.
Similarly, when ground conditions are less than ideal, with silt layers and a high water table, screw piles or driven piles may be the only option.
The Importance of Soil Knowledge
The essential thing is to understand the soil conditions on the site. Often, foundation contractors and builders have extensive experience in the area and can accurately predict what might be encountered.
However, it’s always just an educated guess. The most important thing is that the builder can recognize when conditions are not as planned and make the necessary adjustments. Even if it means a change or delay. While no one likes delays, they’re always better than a foundation that won’t stand the test of time.
In areas where soil conditions may be inconsistent, a geotechnical survey is often conducted. This is a soil test done by engineers that identifies what foundation types are feasible in a specific location. While not always necessary, in uncertain conditions it’s money well spent.
Questions to Ask Before You Build
To help build confidence in your project, here are a few questions to ask your foundation contractor or builder:
- What type of foundation will my home or cottage be built on, and why did you choose that foundation type?
- What type of soil conditions might be a red flag when digging the basement?
- Are there any conditions we may encounter that would necessitate a foundation change?
- Would a geotechnical survey be beneficial to confirm the foundation type?
- Who is inspecting the soil conditions when the foundation is being dug and when the piles are being drilled?
A Solid Start for a Lasting Build
Foundations aren’t something that we want our clients to need to think about. But someone needs to be thinking about them and paying close attention. It’s the most essential thing that no one will ever see once the house is complete.
Ask as many questions as you need to, so you can feel confident in your build and focus on all the exciting details that come next. With the right guidance and a solid foundation beneath you, you can focus on what truly matters. Creating the space where your family’s memories will unfold for years to come.
