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How To Guide: Residential Concrete Footing Construction

featured image how to footings field crew smoothing footings

IMAGE: EXCAVATED FOOTING

Excavated high wind zone footing with horizontal and vertical rebar installed.

What is a footing?

"the bottommost part of a foundation wall, with a continuous course of concrete wider than the base of the foundation wall."

To explain a little further, the footing is a standalone structure that ultimately provides support for the masonry foundation walls that are built “on top” of the footing. It is what separates your home’s foundation from the ground. The two most common types of footings are the perimeter footing and pier footings. We will dive into those in the next section.

Half Size Footing Excavation

PERIMETER FOOTING

To describe what a perimeter footing looks like, I would say that it is an excavated channel or trench dug to a prescribed width and depth. Look at the photo above to see a perimeter footing that has been excavated, but not yet poured. After the excavation, the footer is then filled with concrete to a specific depth. The perimeter footing extends all of the way around your home’s exterior building envelope.

PIER FOOTING

A pier footing is a “square shaped” excavation that offers the same utility that perimeter footings do, except only in certain specified spots and is not continuous. You can see in the picture above where I have outlined a pier footing for you. In the diagram below I have an example of how a marriage wall of pier footings shows up on a blueprint.

pier footing example

MARRIAGE WALL

In most crawlspace construction, there are “rows” of piers that we call the marriage wall. It’s usually at the junction of areas that require support from the footing. Depending on what type of foundation you are building, there can be as many as 50 piers! In our area, the smallest piers we use are 18″, but they average 24″ and are as large as 48″.

If you’re interested in learning more about masonry materials, please read our article on brick types, “Explore All of The Various Types of Masonry Bricks”.

Footing Construction Process

A brief description of how residential footings are built. We take you from project layout to footing excavation and through inspections. Residential footing construction explained with pictures.

(1) Project Layout

Home Layout
Locate Boundaries + Identify Setbacks

The project layout’s purpose is to ensure that the home is being built in an area that satisfies property boundaries and setback requirements and adheres to the sitemap approved in permitting.

FINDING HOUSE CORNERS

Our company uses 100′ tape measures in pairs to find our house corners and to make sure everything is laid out to the blueprint specifications. We hammer in the steel rebar at our corners and use our tapes to hang on them to measure.

SPRAYING THE EXCAVATION DIAGRAM ON THE GROUND

Solvent based marking paint is used to paint the lines for the perimeter footing and also for the pier footings that are on the interior of the perimeter footing. Arrows are painted on the lines that designate which side of the line to dig on.

A TIME TO ENSURE HOME LOCATION AND IDENTIFYING ANY OBSTACLES

In the process of laying out the footing diagram, any issues with access or other obstacles will be identified. On wooded lots, it is extremely common to have trees still standing that exist on the inside of where the footing will be. Other things to watch for include underground electrical lines, septic line and tank locations

(2) Excavation

PIER FOOTINGS FIRST / PERIMETER LAST

First things first. The interior pier footings are the first thing to be excavated. The perimeter footing and any other exterior pier footings are dug last. If you do it in reverse order, you risk damaging the perimeter footing in the process.

FOOTING BOTTOM & STEP DOWNS

When you excavate a footing, the bottom should be level and the proper depth . As you probably know, the ground is not perfectly flat (even if it looks like it is). With grade changes that equal 8″ we are required to add “step downs” to the footing. It is simply a requirement to dig the footing 8″ deeper from that point, continuing until your next step down.

STEEL REINFORCEMENT

If you are in a high wind-zone area, you may be required to install vertical and horizontal steel to your footing for reinforcement purposes. Your local code will tell what you have to do. After inspections are passed, but before the concrete pour is when you install the reinforcement steel.

(3) The Concrete Pour

smoothing footing piers
Mark Proper Footing pour depth

What you want to do first is to go around the entire perimeter footing and mark your proper depths. Proceed to do the same with all of the pier footings. When digging with a machine, the footing bottom is not going to be exactly level. This is why you should place nails in the “dirt wall” to mark the required concrete depth. In our area, the concrete thickness required is typically 8″, but the footing has to be below grade a minimum of 4″ (below the frostline). It’s a lot colder in northern states. Your footings will be a lot deeper than ours down south. Something to keep in mind.

Pour concrete for pier footings first

So you have everything marked and ready to go. You are ready to get your ready-mix concrete ordered and delivered. Once the concrete truck arrives, you will talk to the driver to figure out where to start. We always start with the pier footings (the square shaped ones on the inside of the perimeter footings). Usually, we have a guy following behind the guy pouring concrete. His job is to level and smooth the pier footings, and to ensure that it is poured to the correct depth.

Pour Stepdowns and perimeter footing

After you are finished pouring the inner pier footings, you can move on to the larger perimeter footing. On lots where there is slope present, you will place step-downs at every 8″ of fall. Basically, your footing steps down like a stair step. We always pour these first to be able to create a crisp edge for the height changes. The next part is the perimeter footing and is going to require the most concrete. It is a continuous solid run of concrete. You task the concrete truck driver with moving the truck slowly alongside the footing, while he is pouring concrete down the shoot (that you are holding onto and directing).

Smooth and Level The Freshly Poured Footing

The final step after you have poured all of the concrete is to level and smooth the entire surface throughout. This will provide an easy flat surface for masons to build foundation walls on top of. When you pour concrete, it typically is pretty lumpy and not exactly level. Gravity will do some of the work for you, but a tine welded bow rake works wonders. It allows you to dig the rake in and pull material in the direction you need it to go. When you are done moving material, you can use the back of the rake to lightly “tap” the surface to get the gravel in the mix to sink. This will provide a much smoother and flatter surface finish.

(4) Inspections

POST EXCAVATION INSPECTION

Typically, residential footing construction requires two inspections. The first inspection is after the excavation is complete. The post excavation inspection is to test the soils in the bottom of your newly excavated footing trench to make sure they have enough strength to hold the footing in place.

POST CONCRETE INSPECTION

The second and final footing inspection takes place after the footing is poured. Basic smaller footings are typically 16″ wide, where the foundation wall will only be a total of 12″ wide. This gives the foundation wall extra room to sit on. Trust me, you wouldn’t want to build a wall on the edge of a footing.

THE REASON FOR INSPECTIONS DEPARTMENTS
WE ARE ALL HUMAN

County inspections requirements are put in place for both homeowners, homebuilders, and other contractors protection. Sometimes people make mistakes and it’s the inspector’s job to catch them and fail the inspection until it’s fixed.

HOMEOWNERS DEPEND ON THE PROTECTION

Homeowners depend on the inspectors to ensure that their home is being built properly and safely because they will be living in the structure. Ultimately if the structure fails, the homeowners will be the ones injured or worse.

BUILDERS NEED TO CONFIRM SUBCONTRACTORS DOING WORK PROPERLY

Homebuilders typically hire subcontractors to take care of specific parts of the homebuilding process. There are lots of these and you could imagine that someone could do something improperly but the general contractor doesn’t see it or doesn’t know the specifics of that particular duty. The GC’s main role is to hire competent subcontractors, manage budget and expectations, and stick deadlines. 

“Pictures deface walls oftener than they decorate them.”

That's it!

Now You Know How Footings Are Made!

If you have seen a footing being poured, you are one of the rare ones to even have ever seen a footing. Most people never see it because it’s under their house, they know nothing about it, and don’t realize the importance of it. Everyday that you walk around in your home and you don’t hear squeaking floorboards, it’s a good sign that your footing and foundation was built properly and should last for a lifetime, if maintained properly of course.

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