Your house is about to be anchored to the ground in a way that’s permanent and, importantly, difficult to change. Once the concrete cures, the footprint of the house is set and you can’t go back to the drawing board without significant costs.

If you take nothing else from this course, let it be this: your budget depends on getting the house right the first time. Concrete is practically permanent.

To do that, you'll need to

• Plan ahead for each phase
• Review the plans and the survey
• Double-check the work as it happens
• Ask questions and seek advice

When the foundation work begins, you may hear this called "getting out of the ground" and it's a major step in the construction process.

At this point in the project, the building becomes real and you’ll see it happen over a week or two. Concrete is one of the most common and essential building materials. It’s strong, durable, and can be formed into a wide variety of shapes and sizes. There is a good chance that concrete will be a part of your home’s construction. A few of the most common uses are:

• Footings for columns and walls 
• Retaining walls
• Driveways
• Garage floors
• Interior floors

What to Expect

Your GC will hire a concrete sub-contractor who will arrive on the property to review the plans and discuss any details, difficulties, or exceptions. The work of the concrete team is driven by the foundation plan, which marks the locations and specifications for the concrete work. Here's an example:

The foundation plan may be marked up by the contractor to indicate the different specifications.

Exceptions

Concrete and foundation work can take many forms and your GC and architect will help define what is best for your home. The examples in this section mostly relate to a poured concrete foundation. Before discussing this process, be aware that your project may use other products and processes. These may include:

Cinder Block Walls

In some locations, foundation walls are built with cinder blocks (also known as CMUs - Concrete Masonry Units). These blocks have hollow sections and are stacked like bricks, with masonry holding them together, to create the foundation wall. They are usually considered as strong and reliable as poured concrete.

Because they are made of multiple pieces versus a large unit like poured concrete, CMU walls can be prone to buckling, especially if the ground is unstable beneath them. It's possible to increase a block wall's stability by inserting rebar and masonry into the hollow sections as the wall is built.

Frost Footings

In extremely cold locations, your home may be required to have frost footings, which extend deeper into the ground than normal footing, sometimes up to 4' deep. This is because when the ground freezes and thaws, it can become unstable and impact the stability of your foundation.

Monolithic Concrete Foundations

Another form of foundation is referred to as a "mono pour", which means that the home's entire foundation is created in a single session of concrete pouring. This takes the form of a thick slab for the entire home, with extra reinforcement under load-bearing walls. This type of slab is quick and reliable but prevents the home from having a basement or crawl space.

The Work Begins

The foundation process starts with the construction of “forms”, which are like wooden or metal shells that concrete is poured into. Usually, the forms are built with wood, according to the architect and engineer’s specifications. The forms often contain reinforcing bars or "rebar," which are iron rods that add strength and stability to concrete walls. 

The forms are usually completed in two phases:

1. Footings - These are wide and strong feet for the house that act like snowshoes. They serve as the foundation of the second phase: stem walls.
2. Stem Walls - These are the concrete walls that the house's frame sits upon. They are added once the footing work is complete.

Slab on Grade

The examples in this chapter are focused on homes with crawl spaces, basements, or open areas under the home. Some homes are built on top of a slab of concrete with no space under the home. This is called slab on grade.

This type of foundation is most often used in warmer climates where the ground does not freeze. It can be an affordable option that reduces the potential of pests coming into the home from the ground. However, it also prevents the addition of ducts and other systems under the home.

Strength in Reinforced Concrete

The forms and concrete get their strength from rebar. These rods are embedded in the concrete and make it very strong. One of the most time-consuming tasks in this part of the project is placing the rebar and tying them in place. This happens on walls and footings.

This is a footing:

Once the forms are complete and reviewed by the GC and possibly an inspector, the concrete contractor will arrive with a concrete truck and start pouring concrete into the forms or holes in the ground. At this stage, concrete is a liquid and fills the forms. For larger forms, the team is likely to use a tool that vibrates the concrete and causes it to release air that is trapped and could cause future problems.

Over a few days, the concrete will dry and “cure”. Then, the concrete crew will arrive, remove the forms, and clean up the concrete footings. At this point, the house is a permanent part of the landscape. Rejoice!  

Preparing for Stem Walls

The footings are designed to attach to the stem walls with rebar, which sticks out of the top of the footings. These bars are a hazard and your GC should add rebar caps to prevent injury.

With the footings and rebar in place, the concrete crew may arrive and add more forms for the concrete walls and columns that hold the house in place. Part of this process is adding anchor bolts to the wet concrete. These bolts will be used to secure the frame.

Once the concrete stem walls cure, the concrete crew will return, remove the forms and reveal your new foundation. It's an exciting time, as the house will look more permanent than ever before.

Planning Ahead

Like the site work, a bit of planning can go a long way. If you know the concrete team is coming soon, it may be worth reviewing the site plan and making any additions for the concrete project. 

• Retaining walls 
• Sidewalk or garden paths 
• Entries
• Concrete pad for above-ground propane tank, heat pump, outdoor machinery

There is no more affordable time to get these projects complete than when the team is already there. Here are a few things to consider:

Interior Concrete Floors

Concrete floors are popular for a few reasons. They add a beautiful industrial and contemporary look that holds up well to shoes, pet nails, and furniture over time. They are easy to clean, resist water when sealed, and conduct heat efficiently when combined with in-floor radiant heat. 

However, there are some cons. Our GC once told me that three things in life are certain: death, taxes, and concrete cracking. It happens and the minor cracks are not usually a problem.

Floors can be resealed/refinished. Additionally, concrete, compared to wood, is an extremely hard surface and that hardness translates to your feet. Walking barefoot on a concrete floor for long periods can lead to fatigue, so most homeowners plan on wearing footwear with concrete floors. I’ll circle back to talk about concrete floors a bit later. 

Interior concrete floors are heavy and require special planning. If you're considering a concrete floor, be sure the team knows your plans.

Concrete Aesthetic

Concrete walls in the form of basements, retaining walls, etc. are often a visible part of the design of your home. You have the option to design the look and feel of the surface of the concrete. The standard is a smooth-ish finish that looks like standard concrete, complete with pockmarks and imperfections. However, there are other options. For example, the forms that are used to build the wall could be made of a material that essentially stamps a design onto the wall as the concrete dries around it. This could be wood grain, a geometric pattern, or the rough look of the forms themselves. This decision is a nearly permanent one, so plan accordingly.

This is an example of leaves that got into concrete forms by mistake and created a nice little leaf design.

Recessed Lighting

Imagine a driveway with a small retaining wall that leads to a garage. There is a path beside the retaining wall that will be used often and needs to be lit at night. You can always add landscape lighting. But there is another option that’s cleaner and requires a bit of forethought. 

The retaining wall could have light fixtures recessed into the concrete, creating a seamless, built-in look. If this is a priority, you’ll need to have everything planned before the concrete is poured. This includes the light locations, fixtures, and conduits for connecting the future lights to the electrical system. Your GC can help with this process. 

Garage

If you have a garage, the concrete contractor will likely make it happen when the foundation is poured. There are a few options to consider:

• Color - Dye can be added to concrete to make it a different color. For example, standard concrete is a somewhat bright white color. Dye is relatively inexpensive and can be used to darken and soften the look of a floor or wall. Ask your GC about options.
• Seams - Concrete expands and contracts and seams give it room to move. Think of a sidewalk. You can choose where the seams are drawn. For example, the seams can be placed to outline parking spaces or to follow a path.
• Finish - The concrete team may be able to finish the concrete with different textures and looks. The troweled finish is the standard. Others could include brushed, stamped, polished, colored and many more. You might also consider applying an epoxy finish that is applied on top of the concrete. Some homeowners choose to make their floor Ferrari red or even a rich purple. 

Concrete's Carbon Footprint

Concrete is an essential building material because of its strength and durability. It lasts a very long time and that’s a good thing. However, the production of concrete, or more specifically, the cement that holds it together, comes with a sizable carbon footprint.

Among these ingredients, cement has the biggest carbon footprint because it’s produced by heating limestone and other ingredients in an extremely hot kiln, which requires fossil fuels to run.

A quick primer: As a general rule, concrete is made of 10% cement, 20% air and water, 30% sand, and 40% gravel. Among these ingredients, cement has the biggest carbon footprint because it’s produced by heating limestone and other ingredients in an extremely hot kiln, which requires fossil fuels to run. Limestone also releases carbon when it is heated. 

Oddly enough, the sand used in concrete is not as abundant as you’d think. The average home requires about 200 tons of sand, mostly in the form of concrete. That sand is not the kind you find in a desert, which is smoother and rounder due to erosion. The sand used in concrete must be angular. This type of sand is found on the bottom of oceans, lakes, and rivers. 

Like many elements of construction, the cost of concrete must be viewed in the context of the alternatives, which come with trade-offs. If the project needs the strength of reinforced concrete, then you must consider what could take its place. This might include steel beams, for example. Steel is not inexpensive and also has environmental impacts. If this a concern for you, talk with your GC and architect about the costs of the materials that are specified in the plans and what alternatives could be explored.