When building a home from the ground up, considering the main structure and systems would come up as one of the first decisions to make. It also stands as one of the critical factors to consider. House foundations come in different types and various techniques so learn all about them in order to find the right type for your home design.
Table of Contents
- I. House Foundation Guide
- II. More Details
- III. How to Choose a Foundation Type
I. House Foundation Guide
You have many decisions to make before construction begins on your new home. Deciding on the type of foundation may be the most important—so knowing what options and materials are available is essential.
The average weight of a house is over 200 tons—including your belongings—so a strong foundation is crucial if you want a home that will last.
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A. House Foundation Types
1. Basement Foundation (Two Types)
Basement foundations have structural walls extending underground. Two types are common: full and daylight. A full basement is entirely underground, either with no windows or small ones at ground level.
Basement foundations can be finished (see finished basement ideas here and see the different types of finished basements here) or unfinished. Unfinished basements often serve as storage areas or house water heaters, furnaces, and other household equipment.
A daylight basement is on a slope. Some walls are below ground, blocking daylight, and others are partly or entirely above-ground.
Achieving a daylight or walkout basement requires the right slope on your lot. But if you don’t mind spending a lot of money on prepping your home build site, it is possible to grade the lot to accommodate a daylight basement.
Basement foundations require either concrete masonry units (CMUs) or concrete walls (poured concrete). Basement foundations are the most expensive option, but they also let you extend your living space if you decide on a finished basement.
2. Crawlspace Foundation
A crawlspace foundation involves short foundation walls on footings. These types of foundations are usually unheated but have ventilation to avoid moisture buildup. They use poured concrete or mortared concrete blocks, and they’re less expensive than a full basement.
Many people consider a partial basement to be a crawl space since you can store some items there but can’t convert it into a living space.
Concrete slab foundations, or slab-on-grade foundations, are a common option in many areas. They’re best for climates where the ground doesn’t freeze and thaw throughout the winter. These types of house foundations help protect against termites.
Accessing water and drainage pipes can be complicated, however, because those features typically lie underneath a few inches of concrete. Slab-on-grade foundations are one of the least expensive foundation options.
4. Wood Foundation
Wood foundations are often standard in northern areas. They can have a crawl space underneath, too. It’s also common to find basements that layer pressure-treated wood on top of concrete floors—but technically, such a combination would count as a concrete foundation.
B. Foundation Materials and Methods
Though foundations are often cement or wood, there are variations. Here are common materials you can find for foundations.
1. Poured Concrete
2. Precast Concrete Panel
3. Concrete Masonry Units
Stone basements are no longer common, but you might find them in older houses. These types of house foundations use a mixture of stones and a mixture of cement to form a solid barrier. They can crack and chip, so most builders shy away from such materials in modern homes.
Of course, nothing is stopping you from adding a stone façade to your basement or foundation.
Since about 1960, pressure-treated lumber has been a common foundation material. Wood foundations are cheap, easy to assemble, and can resist moisture and insects. However, wood doesn’t last forever, so it’s gradually become less popular as a foundation-building material.
C. Foundation Construction Methods
You can build a foundation in a few different ways. Here are some other standard construction methods.
1. Footing and Stem Wall
A stem wall foundation is common in areas with low to moderate frost because they are very stable. The multi-step process involves pouring a footer, then laying blocks to form a wall to the finished slab height.
Footing and stem walls take a while to complete, but the result is a solid foundation that is resistant to issues like water and ground movement.
2. Pier and Beam
Pier and beam foundations are more common in commercial and industrial applications. However, for larger residential homes, many builders will use drilled shaft concrete piers and beams.
A pier and beam foundation is ideal where the soil is clay and has high plasticity. But you’ll also need a structural engineer to oversee the project since the design and soil analysis are vital factors for a safe and robust build.
3. Pier and Beam for Manufactured Homes
For manufactured home installations, a different type of pier and beam foundation is useful (and often affordable). First, anchors go into the ground to hold against wind and other weather. Straps attach to your home’s steel frame to hold it in place. Then, outriggers and cross-members go on to add extra weather resistance.
The base can be steel, but you can also opt for concrete or ABS plastic pads underneath. Installation can be quicker with this foundation, but it’s only applicable to manufactured or mobile homes.
4. Slab on Grade/Monolithic Slab
When construction workers pour a slab on grade—AKA, a monolithic slab—they complete the pour in one go. The footing, stem wall, and concrete subfloor all go down at the same time, and the slab is a few inches thick. Instead of footers, there are thicker areas of concrete where load-bearing walls go.
Slabs contain either rebar or cables for strength, and they can handle homes, garages, sheds, and more.
5. Pre-Poured Slab
II. More Details
Here are the factors that affect foundations, plus pricing and build considerations.
A. Climate Required
Some house foundation types aren’t suitable for specific climates. For example, environments that experience extreme temperatures aren’t ideal for slab foundations. As the water freezes and thaws, the concrete can crack from the pressure. In contrast, warmer climates may not benefit from wood foundations since termites can pose a threat.
Climate is a crucial influence over your build plans, so don’t get too attached to a particular foundation type until you see what will work where you live.
B. Lot Grade and Soil Type
You might be fortunate enough to live in an area with a mild climate, but that doesn’t mean you can choose any foundation. The grade of your lot and where you decide to put your home can affect the compatibility of certain house foundation types.
The soil can also affect the foundation construction. If there is rock below your build site, for example, you might need a structural engineer to examine the lot and figure out a plan for building over it. In other cases, unstable soil could mean you need to select a different build site.
Lot grading can also impact your ability to have a specific foundation build. You might want a daylight basement, but if the lot isn’t graded just so—or if you don’t have modifications in your budget—you might only be able to choose a traditional basement.
C. Utilities and Accessibility
With some types of house foundations, it’s easy to get in and fix things when they break. For example, you might need to enter a crawlspace to service your home’s plumbing. But in a poured concrete foundation, for example, the pipes might lie under inches of concrete.
How accessible your home’s internal structures depend on the type of foundation and the layout of the features underneath or inside it.
D. Home Style and Design
The architecture or overall design of your home may dictate the type of foundation you need. Or, you might be installing a mobile home over the foundation you choose. While you can place a manufactured home on almost any foundation, many homeowners opt for pier and beam foundations unique to manufactured homes.
Of course, you can choose whatever foundation you prefer, but costs—and engineering issues—can creep up, too.
E. Cost and Pricing
The cost of your foundation depends on many factors, including the average cost of labor in your area. Here are the deciding factors when it comes to foundation pricing.
1. Square Footage
The lower the square footage of your home, the cheaper your foundation may be. You can expect to spend anywhere from $4 to $7 per square foot on a concrete foundation.
At the same time, a single-story home foundation is often more expensive than a multi-story one. It might seem counterintuitive, but the upper floors don’t need additional concrete foundations, so going vertical might save you money overall.
Plus, per square foot, it’s cheaper to build a two-story house anyway.
2. Construction Type
Of course, the type of foundation you ultimately choose will influence the price more than any other feature. The most expensive foundations are basement builds—especially if you want a finished basement—while the least costly is a concrete slab.
A crawlspace foundation would be mid-range, though you might find pre-made concrete slab solutions that are around the same cost.
3. Foundation Depth
The deeper your contractor must dig, the more expensive the foundation project will be. But in many climates, you will need to have a deep foundation—below the frost line—to protect your home and its structural integrity.
4. Other Pricing Considerations
A foundation is a foundation, right? Not exactly. Pricing also depends on materials costs, extra features, and transportation costs.
For example, installing radiant heating in the floor, which can save on heating and burst pipe costs, adds a significant bump to the bottom line. If you need additional waterproofing or sealant due to climate or site drainage issues, those can also add up.
5. Average Price of a Home Foundation
A home foundation costs anywhere from $4,000 to $175,000. Pricing varies widely based on the materials, time required, and the foundation type.
For example, a slab basement typically comes in under $21,000, while a basement foundation can cost up to $175,000. Here’s an overview of typical foundation project costs based on foundation type.
- Slab foundation: $4,500-$21,000
- Crawl space foundation: $8,000-$21,000
- Basement foundation: $10,000-$175,000
Keep in mind that foundation projects also require permits, which your builder may or may not handle for you.
III. How to Choose a Foundation Type
If you are building from the ground up, you can choose the right foundation type for your home. Here’s how.
A. Site Considerations
Depending on your home building site and layout, one type of foundation may work better than another. Here are the natural factors that impact your site.
1. Water Tables
A groundwater table is a boundary between unsaturated and saturated soil. Water tables rise and fall with the seasons, and depending on your lot, they may impact drainage at the building site. Water can even seep out of the ground and affect your foundation.
2. Soil Conditions
A drilled pier foundation, for example, is ideal for ensuring your home rests on the hard rock rather than in soft surface dirt. The type of backfill you use also influences the stability of your foundation. Most people choose store-bought filler material such as limestone or aggregate to backfill the foundation.
B. Local Climate
Your local climate can also influence what type of foundation is best. Frost, for example, is a significant factor. If you live in an area where the ground frequently freezes and melts, you could see cracks in your home’s monolith slab foundation. In that case, a post and pier foundation might be a better solution.
Or, if you live somewhere with a high risk of tropical storms, a foundation that can withstand flooding is preferable. Again, a post and pier option may work better than a full basement or slab. Then again, in more moderate climates, a monolith slab is often sufficient and a budget-friendly choice.
C. Foundation Purpose
The purpose of a mono slab is very different than that of a daylight basement. Knowing what purpose you want your foundation to serve is vital since it affects how you’ll use your home.
1. Extra Living Space
If you want to add extra space to your home’s floor plan, choosing a basement foundation might be the right fit. A finished basement adds square footage to your house and can function as an extra bedroom, game room, media room, or guest lodging.
Plus, finished basements enhance your home’s resale value. Only about 30 percent of family homes built after 2013 have full or partial basements. In comparison, 54 percent are on slabs and 15 percent include a crawl space.
2. Outdoor Living
For optimal outdoor living, choosing a walkout (or daylight) basement might be the way to go. You can include windows, stylish doors, and even a patio on your walkout basement. This way, you can enjoy entertaining in your backyard—or even rent out your basement as an apartment unit.
Obviously, a concrete slab or wood foundation doesn’t offer much in the way of storage space. If you want to be able to stow belongings—or appliances like the water heater—below the floor, a foundation with a crawl space is a must.
Most homeowners want stability in their foundations. But for people who live in floodplains, a stable foundation is the top priority when building. Elevated slab foundations are one innovative solution to flood issues.
An elevated slab foundation, like Tella Firma’s, combines a slab foundation with a pier-and-beam system. The elevated foundation takes a little longer to build and is more expensive than standard foundations—but it can save you money if water damage is a concern.
The suspended foundation is ideal for clay soils, which expand and contract throughout the seasons, and wetter conditions.