Know Your House: What Makes Up a Home's Foundation
Learn the components of a common foundation and their purpose to ensure a strong and stable house for years to come
Bud Dietrich, AIA
25 April 2013
Houzz Contributor. My name is Bud Dietrich and I am an architect located in the Tampa Bay area of Florida. I am licensed to practice architecture in Illinois, Florida, New Jersey & Wisconsin. Since 1996 I have worked from my home office and provide full architectural services exclusively to the single family residential market. My passion is to transform my clients' houses into their homes. I strive to have the "new" home accommodate my clients' lives without fighting them at every junction. I look to add curb appeal to encourage a beautiful streetscape. And I design any addition to look and feel like it has always been there.
Our projects have won numerous design awards as well as having been featured on television (CBS News Sunday Morning, HGTV, CLTV, etc.), in magazines (Better Homes...
Houzz Contributor. My name is Bud Dietrich and I am an architect located in the Tampa... More
In many respects the foundation is the most important element of any building, be it a house or a high-rise. Simply put, the foundation is what everything rests on. So getting the foundation right will go a long way toward having a sound and stable building for many years.
From pilings to piers to spread footings and more, foundations can be built in many ways. The most common, though, is the simple foundation wall made of poured concrete or concrete block, and a poured concrete footing system. The vast majority of homes in North America are built using this approach, as it’s relatively inexpensive and there are scores upon scores of tradespeople able to quickly and efficiently build it. Therefore, the focus of this piece is on the typical wall and footing foundation system.
And remember that you should consult a local architect or builder to review any planned foundation and how local building codes will impact the system design and construction.
From pilings to piers to spread footings and more, foundations can be built in many ways. The most common, though, is the simple foundation wall made of poured concrete or concrete block, and a poured concrete footing system. The vast majority of homes in North America are built using this approach, as it’s relatively inexpensive and there are scores upon scores of tradespeople able to quickly and efficiently build it. Therefore, the focus of this piece is on the typical wall and footing foundation system.
And remember that you should consult a local architect or builder to review any planned foundation and how local building codes will impact the system design and construction.
The three structural parts of this kind of foundation:
A very important design consideration is placing the bottom of the footing below the frost line. This line exists at some distance below the surface and is where the ground, or any moisture in the ground, doesn't freeze. Placing the footing below the frost line is essential to prevent any heaving or other movement caused by the freeze-thaw cycle.
Note that the depth of the frost line varies by location. The frost line is closer to the ground surface in warmer climates and much deeper in colder climates. But it's essential to know where your frost line is when designing your home's foundation.
- A continuous concrete footing
- A foundation wall of either poured concrete or concrete masonry units (CMUs)
- A concrete floor slab
A very important design consideration is placing the bottom of the footing below the frost line. This line exists at some distance below the surface and is where the ground, or any moisture in the ground, doesn't freeze. Placing the footing below the frost line is essential to prevent any heaving or other movement caused by the freeze-thaw cycle.
Note that the depth of the frost line varies by location. The frost line is closer to the ground surface in warmer climates and much deeper in colder climates. But it's essential to know where your frost line is when designing your home's foundation.
Keeping water out. A foundation system is in many ways like a big bathtub. But rather than keeping water in, we want to keep water out. Several components built into a foundation do just that.
First, the exterior, ground-side face of foundation walls will have a waterproofing material installed on it. This material should be strong enough to prevent punctures or tears and flexible enough to allow for any movement the foundation will experience. This moisture barrier should form a skin not only over the wall but at the top of the footing as well.
Next in the line of defense against water is a perimeter drain near the bottom of the footing. This drain is a perforated pipe surrounded by crushed stone to keep dirt and debris from blocking the perforations. Groundwater will find its way to this drain and be channeled away from the footing. Making sure that these drains are clear is a critical step in making sure water doesn't get into the basement or crawl space.
Other parts of the waterproofing system:
First, the exterior, ground-side face of foundation walls will have a waterproofing material installed on it. This material should be strong enough to prevent punctures or tears and flexible enough to allow for any movement the foundation will experience. This moisture barrier should form a skin not only over the wall but at the top of the footing as well.
Next in the line of defense against water is a perimeter drain near the bottom of the footing. This drain is a perforated pipe surrounded by crushed stone to keep dirt and debris from blocking the perforations. Groundwater will find its way to this drain and be channeled away from the footing. Making sure that these drains are clear is a critical step in making sure water doesn't get into the basement or crawl space.
Other parts of the waterproofing system:
- A polyethylene vapor barrier installed between the concrete floor slab and the ground to keep ground moisture from migrating up into the slab
- A finish grade that slopes away from the foundation so that water drains away from, not toward, the house
- A ground level of at least 6 inches below the top of the foundation wall
A nice touch for brick exteriors. There are many variations in any foundation system. One variant is the incorporation of a brick ledge into the foundation wall design. This is a nice design detail if you plan to use an exterior brick or stone finish. Rather than the brick sitting on top of the foundation wall, the brick can start just below the finish grade, making it appear that the foundation is constructed of brick, as it would have been in an older home. Of course, this type of detail has to be worked out carefully so that the foundation stays dry over the long haul.
Just make sure that you and your architect or builder work out the best foundation system for your particular project. Having a good, stable and solid foundation that stays dry will be worth every cent invested in it.
Next in Know Your House: What Makes Up a Floor Structure
Just make sure that you and your architect or builder work out the best foundation system for your particular project. Having a good, stable and solid foundation that stays dry will be worth every cent invested in it.
Next in Know Your House: What Makes Up a Floor Structure
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Bud, I liked reading about your perspective on how a foundation is like a bathtub that is supposed to keep water out. This seems like it might be a good tip to remember when building a home. I have a brother who works in construction and this might be good advice for him to think about. http://ne-homeinspections.com
Bud, I agree with you on how it is important as a homeowner to understand your home. If you understand how your home's foundation works and what it is supposed to look like, then you can spot issues with it. The foundation is the most important part of your home and repairs need to be made quickly if there is a problem. Doing that could end up saving you from an expected disaster your home. http://www.sealtechbasement.ca/en/services.html
Despite your contractors best efforts to ensure you
have a water tight basement, As your home ages and goes through each season
your home becomes more susceptible to foundation cracks. Through out spring
as the ground thaws and we receive high levels of precipitation its the best
time to check to see if you have any cracks in where water can get in.