Stepped Concrete Footings
Footings are the most basic structural support for buildings in contact with the earth. For houses on a level building lot the footings are very simple and end up all at one elevation. However, for more complicated designs the footings end up changing elevations and therefore require a “step” in the grade. Stepped Footings allow depth of footings to transition from one elevation to another.
Uses for Stepped Footings
The picture above shows a standard stepped footing for a residential home located in the Northeast. In this example the footing transitions from one grade level down approximately 4 feet to a lower level. The lower level is needed in order to provide frost protection in an area with a walk-out type basement. This is very common in cold climates with walk-out basements.
Another use for stepped footings happens when there is a change in grade from one slab to another. In areas with difficult rock sites the basement might be stepped up (resulting in lower head room) in order to avoid costly ledge blasting.
How Stepped Footings Are Built
The example above is by far the most common approach to building stepped footings here in the Northeast. The stepped footings are built all at the same time with some fairly rough yet affective methods. The footing is built using the following method:
- The lower footing is formed with standard forms like the one shown at right. The footing forms extend all the way to the back of the slope under the stepped footing.
- The upper footing is also formed in the same fashion. However, the side forms are extended and cantilevered out over the lower footing forms until the end of the upper footing is at least 12 inches or so past the back of the earth slope. Sometimes the location of the vertical face is calculated so that normal width wall forms will fit from that vertical surface back to the next closest corner.
- Pieces of plywood are nailed over the gap between the two. Also pieces of metal banding are installed on the back of the stepped footing (against the soil) and the sides of the plywood. This helps keep the forms from pulling apart due to the pressure of the concrete. If you look closely at the pictures above you can see the loose banding after the forms were removed.
- Next a vertical piece of plywood is nailed between the forms to create the vertical front face of the stepped footing.
- Concrete is then placed in the upper and lower forms at the same time. Because the concrete is fairly stiff for footings it typically does not flow out through the lower form. In cases where that’s a problem a baffle is sometimes nailed to the top of the lower forms to stop that from happening.
As you can see from the photo stepped footings are not all that complicated. However, they do make grade transitions for foundations much easier.
Just bookmarked your site and am looking forward to perusing it. I have about a decade of construction experience, but have only formed and poured a few foundations, including ICF, SOG, crawl space, etc. That said, I have a question that seems right up your alley. I am building a 28’x52′ house on a site that sloped about six feet over the 52′ length. After a soils assessment (excellent bearing) and no ground water issues, and grubbing the site, I had my machine operator peel of about three feet off the high end, and if he knocks it down a bit more, I can achieve a level footing for my 48″ stem walls to sit on. With the low-side footings sitting on undisturbed, I will backfill to a height of about 30″ to give myself the requisite frost protection. At the higher end of the lot, I will have 30″ trenches, so just a skiff of backfill will be needed to pretty things up. With some material movement, I can get pretty close to a flat yard in front of the house.
My well-meaning machine operator is trying to sell me on a stepped footing, but I don’t feel like it is merited as right now we are only 40″ out of level along the length of the footprint. I have done stepped foundations, and it is just more bother, for both footing and stem walls, with some taller forms needed, etc. By my reckoning, if I can get the high end and low end grades within 30″ of each other before I pour my walls, I an saving time and money over stepping. What do you think?
PS I read about building constantly and am planning a FPSF (frost-protected shallow foundation) for a small shop on the same site. I have also done rubble trench slabs for outbuildings here in BC. I have been all over NH, by the way.
Alan – The steps are typically necessary when we’re trying to get frost protection and we don’t want to dig the high side excessively deep and pour concrete that’s not needed. This is particularly true with walkout foundations. Your case seems to indicate that you can use a constant footing depth as long as the low side has adequate frost protection when all is said and done. I think you’re on the right path. Good luck.
Thanks for the speedy reply. And it was good to read your take being in line with mine. My gut says to avoid stepped foundations, if you can do it by moving some dirt around. While the site could easily have accommodated a walk-out, that was not the look I wanted.
HOW WOULD YOU WATER PROOF A STEPPED FOUNDATION?
John – not sure I understand. With stepped footings the grade is typically following the change in footing depth, so we transition any water proofing system to follow the proposed grade.
In the process of finding a builder for new home construction. One plan we are considering is a side by side split level that has a full basement separated by a stepped footer. The foundation will be poured concrete 8′ high. My concern is water issues at the lower basement level, regardless of how many times the contractor assures me it wont be a problem with proper drainage. Do I have a legitimate concern or am I overthinking? Also, I spoke with a retired mason who said it would be just about as cost effective to make the basement footer one level, which would give me 12′ walls in one section and 8′ in the other. Although more material would be required, his thought was that it would be less time consuming in terms of setting the full foundation. Any help or input would be greatly appreciated. Thanks
Jason – With proper drainage and a good coating system it’s not a big deal. Here in NH we build houses like that all the time. We’re doing one right now. Couple things to keep in mind.
– You need really good foundation drains (perforated pipe, stone blanket, pipe drains to daylight).
– I recommend a foundation coating system like TUFF-N-DRI® – This is a foundation coating, along with an insulation drainage board. The board helps get water down to the drain instead of staying against the wall.
– I HIGHLY recommend good gutters, and proper grading around the house to keep water away.
Definitely not cheaper to build 12′ walls. We step footings all the time.
Best of luck.
We are busy getting a foundation ready for a 4m high retaining wall, that will also serve as the base for the rest of the one side of a building.
This is being done next to the Okavango river in Namibia, so there is no solid base to work on, only sand. My questions: how do I go ahead to prepare the base for the foundation, can the retaining wall be build with bricks (400mm wide x 4m high) and on top of the retaining wall the normal 9-inch wall should be 3,5m high.
The length of this retaining wall is about 12m, and needs to step about 3 times, as this wall is square with the river ond on a slope of 4m.
Is there a big cost difference when you step footings as opposed to straight runs?
Can be quite significant.
Our foundation was stepped on the side of our house addition where there was a slope. When siding the front of the addition, how can we have siding go all the way to the end of the front of the addition where the concrete is high where front meets the side (I can’t nail into concrete.) We want the siding on the front of addition to be at the same level off the ground as the rest of the main house. I would also like it extend to the end.
In most cases I’d recommend NOT installing siding over the concrete. It just won’t last. I’d recommend you “hide” the concrete with landscaping.
We are building a pier and beam foundation on a slope and wonder if a continuous step footer will be more advantageous than digging/pouring individual footers for each pier? Our piers are going to be 16”x16” block, filled with rebar. Your insight will be appreciated