House foundation types

Updated September 11, 2023

Your foundation is the unsung hero of your home. Often overlooked, it supports the entire frame of your property, prevents groundwater from entering your home, and can provide additional storage or living space. But did you know that the type of foundation your home uses can affect your home insurance premium? Here’s everything you need to know about the most common types of foundation.


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What is a foundation?

A foundation is simply the lowest load bearing part of your home. It serves three main purposes.

Firstly, the foundation bears the weight of the entire house, transferring the force through to the ground beneath. For this reason, most (though not all) foundations are made of concrete and dug into the earth for added stability.

Secondly, your foundation essentially holds your house in place, acting as an anchor between the frame (the walls, ceilings, etc.) and the ground below. In the event of natural disasters (such as earthquakes, hurricanes and tsunamis) or more routine adverse weather conditions (such as floods, wind, and frost-heave) your foundation stops your home from being washed or blown away.

Finally, a well-laid foundation can help waterproof your property and prevent groundwater from rising into the lower reaches of your home.

Types of foundation

There are three types of foundation commonly used in homes across North America; the type used depends on the climate, soil and groundwater levels in your area.

Basement foundation

Basement Foundation Type

Basements are a common feature of many homes, yet some people may not be aware that a basement is actually a type of foundation. Modern basements are usually constructed of concrete that’s poured to form a hollow, below grade structure. But what does that actually mean?

‘Below grade’ simply means below the ground. So, before the concrete is poured, contractors will excavate and treat a hole in the earth. Basements are usually between 6 and 8 feet deep, depending on soil conditions. When the base of the foundation is laid, it forms both the bottom-most load bearing element of your home, and the floor of the basement.

Basements can be both fully and partially below-grade. Some owners prefer the latter option as it often allows more natural light into the property, which has advantages when the space is used for residential purposes.

This brings us onto the second element of basement construction. The term ‘hollow’ refers to the fact that basements must be large enough for an adult to stand in. Chances are, if you can’t stand in the lowest floor of your home, your foundation is either a crawl space or a basement built before the current basement-height regulations were put into effect.

Common terms you may hear when researching homes with basements are ‘finished’, ‘unfinished’, ‘full’, and ‘partial’. Unfinished basements are not designed to be lived in. Often the walls and floor are the bare concrete of the foundation. The basement may contain electrical wiring systems, plumbing pipes and your hot water heater. A ‘finished’ basement is one that’s fit for habitation, usually with drywall, flooring, a finished ceiling, and other comfortable features similar to what you’d find on the main level of the home.

The term ‘finished’ basement is often considered synonymous with a ‘full’ basement, but this is actually a misnomer. A full basement is simply one that’s big enough to stand in- so your basement can be full, but still unfinished. A partial basement is one where only a portion of the space is big enough to stand in. The rest might be similar to a crawl space.

As mentioned above, modern basements are usually constructed of poured concrete, though older homes, and those located in drier regions, may use concrete blocks or bricks. While this method of construction is reasonably solid, it does present an increased risk of water intrusion and can make it more difficult to determine the cause of a loss.

Crawl Spaces

Crawl Space Foundation Type

A crawl space foundation raises your home 1 to 3 feet off the ground; enough space to crawl, but not to stand- hence the name. This type of foundation is often preferred in moist climates, as the home is elevated from the damp ground.

Crawl spaces are fully enclosed and can’t be used as living space. Some serve as a location for plumbing pipes and other utilities. Some homeowners use their crawl space for storage, but this is not recommended, as moisture from the damp ground can enter the crawl space and cause damage to property, especially organic items (such as paper records) or items stored in cardboard boxes.

For the same reason, crawl spaces are prone to mould and bacteria growth which can cause damage to wood floors and surfaces, drywall, and some types of insulation. If you’re considering a crawl space foundation, be sure to take the proper steps when sealing and venting the area. You can learn more about how to waterproof your basement here.

Slab foundation

Slab Foundation Type

A slab (or slab-on-grade) foundation, as the name suggests, is a slab of concrete that sits on the final grade of your property. It’s usually a few inches thick, and is poured thicker at the edges to form a footing. Reinforcing steel rods then strengthen the footing and the frame of your home is attached. This type of foundation is the simplest and cheapest to manufacture, requiring very little on-site preparation. From a structural perspective, concrete slab foundations provide a durable, level surface for floors; homes built on slabs rarely experience problems with creaking fixtures as the home settles over time.

The downside of a slab foundation relates to its strength in extreme conditions. As it’s not dug into the earth, a slab foundation doesn’t provide as stable a base for your home as a basement or crawl space.

Foundations and insurance

If you can, do some research on your foundation before getting a quote, as you’ll need to answer a few questions during the application. The type of foundation used in your home’s construction can impact your insurance premium, and in some cases determine whether coverage is available at all. For example, Square One will ask you what form of foundation supports your home, and what kind of waterproofing has been undertaken in your crawlspace. We’ll also ask if the foundation shows any visible signs of erosion or cracking, as this may compromise its structural rigidity.

An important consideration when choosing a home insurance provider is the degree to which they will rebuild your home. Will you receive actual cash value or replacement cost? Square One goes one step further by offering Guaranteed Building Replacement Coverage to customers who agree to insure to the replacement cost of their home.

This means that, in the event of a total loss (a fire, say), we’ll rebuild your home even if it costs more than your limit of insurance. Even better, if there have been changes in the bylaws relating to the construction of basements since your home was built, we’ll rebuild to meet the current requirements at no additional cost to you.

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Policy Exclusions

All of Square One’s policies are comprehensive (or ‘all risk’). This means they insure against everything except for a list of exclusions. When insuring your home, consider how these exclusions relate to your foundation. For example, damage caused by the following perils is not covered under your policy:

  • Wear and tear
  • Mould
  • Condensation
  • Contamination

When considering the state of your foundation, the primary concern for an insurance provider is waterproofing. Rising groundwater, freeze/thaw cycles and tree roots can all compromise the integrity of your foundation, and once moisture gets in, it can be difficult to treat, often leading to further damage.

In some climates, it can be almost impossible to stop water from penetrating the earth that surrounds your foundation, so it’s vital that such foundations feature adequate drainage. It’s also a good idea to install a sump pump in your basement or crawl space. This pump sits in the lowest part of your home and activates once water is detected, moving it away from your foundation through a network of pipes.

Sump pumps are useful not only for homes in wetter climates, but also for any home that may experience storms or flooding. When properly installed with a back-up power system (such as a battery or generator), Square One may apply a discount to your premium, as a sump pump can significantly reduce the chance of water damage at your property.

Your policy also excludes damage caused by settling, sinking, buckling or cracking of the structure. This exclusion highlights the importance of selecting the right type of foundation for your location, and selecting a reputable contractor to undertake the work.

For a more complete list of exclusions, check your Square One policy, or check out common exclusions in home insurance, where we break down excluded losses you should be aware of.

Commonly asked questions

What is the strongest type of foundation?

While this depends on the property and type of soil under discussion, the strongest foundations are generally those dug into the earth to provide a stable base for the property above. While high-rise buildings like apartment blocks may excavate a pit of 30 metres or more for a foundation, 6-8 feet is usually sufficient for residential properties. Of the three types of foundations discussed in this article, basements provide the strongest platform for your home- hence why their inclusion has been so widely adopted. If you’re thinking about building a home, be sure to discuss foundation types with your contractor and determine which will be the best type for your exact ground and climate conditions.

When buying a home insurance policy, the most significant cost item will be the Building limit of coverage. Your foundation is part of that cost, but on average, the type of foundation is less likely to have an effect on your premium than other factors that you can control, like the type of roof, presence of a sump pump, and whether you have a claims-free history.

How do I make sure my foundation is waterproof?

Many waterproofing issues can be fixed through two simple solutions; adding or repairing gutters and downspouts so that water is able to drain away from your foundation, and grading your soil to slope away from your foundation so that water isn’t encouraged to settle. You might also consider installing a French Drain at your property and installing a sump pump. Other internal measures, like applying sealant to the foundation, can also be of value if professionally performed.

How much does a foundation cost?

The cost of a foundation depends on many factors including the size of your home and the type of foundation you choose. As a general guide, expect to pay around $5 per square foot for a slab foundation, $8 per square foot for a crawl space, and $20 per square foot for a basement, according to Home Advisor.

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