Laying a foundation is a necessary first step in any construction project to support and stabilize the entire structure. It’s a good idea to acquaint yourself with this process before building a new home, adding an extension, or constructing a garage. This guide will walk you through the foundation construction process, from choosing the right foundation type to maintaining and inspecting your final product.

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Foundation Types and Their Purposes

Before you break ground, familiarize yourself with the following foundation types and their specific purposes. Your foundation choice will depend on various factors, including soil conditions, climate, and the structure’s intended use.

Basement Foundations

Basement foundations provide additional living or storage space beneath the main structure. Laying a basement foundation involves excavating a deep hole and constructing walls that extend below the frost line. Basement foundations are common in colder climates and offer advantages such as increased square footage and protection from severe weather.

Crawl Space Foundations

Crawl space foundations elevate the structure slightly above ground level, creating a small space between the ground and the first floor. This foundation provides easier access to plumbing and electrical systems than basement foundations and offers better protection against moisture than slab foundations.

Slab Foundations

Slab foundations are popular in areas with warm climates and stable soil conditions. They consist of a single layer of concrete poured directly onto the ground. Slab foundations are cost-effective and quick to install, making them ideal for smaller structures or areas where frost heave is not a concern.

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Obtain Permits and Materials for Your Foundation

Once you’ve selected a foundation type, contact your local building department to determine what permits you’ll need for construction. These may include the following:

• Building permit
• Electrical permit
• Grading permit
• Zoning permit

Permit requirements will vary depending on local building codes and your project’s specifics. After securing the proper permits, gather the following materials:

• Concrete: Choose the appropriate strength and mix design for your specific project.
• Concrete curing compound: Apply this liquid to the surface to prevent moisture loss during curing.
• Concrete finishing tools: Trowels, floats, and edgers smooth and level the finish.
• Concrete pump or mixer: Use this to mix and transport concrete. You can also use a wheelbarrow in a pinch.
• Drainage pipes: Use perforated pipes or French drains to divert water from the concrete slab. This will help maintain the foundation and save you money, as the concrete slab can be costly.
• Formwork: Wooden or metal forms, stakes, or braces will contain the concrete during pouring until it sets.
• Gravel: Gravel provides stability and drainage beneath the concrete.
• Moisture barrier: This can be a layer of plastic or waterproofing membrane.
• Reinforcement: Steel bars, wire mesh, or fiber reinforcement strengthen concrete.
• Safety equipment: You’ll need gloves, safety glasses, and hard hats for construction.

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Preparing the Site for Foundation Construction

Now that you have your permits and materials, prepare the site to ensure a stable foundation. This phase involves the following steps:

Clearing and Excavation

First, clear and level the land as follows:

1. Begin by clearing the construction area of vegetation, debris, and any unstable soil.
2. Excavate to the required depth, which typically extends below the frost line in colder climates.
3. Ensure the excavation is level and properly sized according to your foundation plans.

Soil Testing and Compaction

Next, test and adjust the soil by following these steps:

1. Conduct soil tests to determine its load-bearing capacity and composition.
2. Add or remove soil as needed to achieve proper compaction (based on the test results).
3. Use a plate compactor or roller to ensure the soil is evenly compressed, creating a stable base for your foundation.

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Step-by-Step Process of Laying a Foundation

Once you’ve prepared your construction site, you can lay your foundation using our step-by-step guide below.

Marking and Layout

To ensure your structure’s overall alignment, start by measuring and marking your foundation as follows:

1. Carefully mark the foundation’s perimeter using stakes and string lines.
2. Double-check measurements and confirm corners are square using the 3-4-5 triangle method.

Digging Footings

Excavate trenches for the footings, which will support the foundation walls. The footings’ depth and width will depend on local building codes, soil conditions, and the structure’s weight. Footings typically extend below the frost line to prevent shifting due to freeze-thaw cycles.

Installing Reinforcement

Once you’ve dug your footing trenches, reinforce them as follows to help distribute the load and prevent cracking:

1. Place reinforcing steel (rebar) in the footing trenches according to your structural plans.
2. Verify the rebar is positioned correctly and secured before pouring concrete.

Pouring Concrete

Next, follow these steps to pour concrete:

1. Mix and pour concrete into the footing trenches and foundation forms.
2. Use a concrete vibrator to eliminate air pockets and create even distribution.
3. Smooth the surface with a screed board and finish as specified in your plans.

Curing and Waterproofing

Finish up by curing and waterproofing your concrete foundation as follows:

1. Allow the concrete to cure for at least seven days, keeping it moist to prevent cracking.
2. Once cured, apply a waterproof membrane to the foundation walls’ exterior to protect against moisture infiltration.

In the video below, general contractor Tom Silva watches a crew in Charleston prepare for and pour foundation footings for a home addition.

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Build Foundation Walls

Foundation walls form your foundation’s perimeter, providing structural support and preventing soil from entering the living space. Here’s how to pour concrete walls:

1. Construct the forms: Start the walls by making sturdy forms to use as molds. Pressure-treated lumber works well. The wall forms should match the thickness and height specified in your plans.
2. Place reinforcement: Reinforce the forms with rebar or wire mesh for added durability.
3. Mix and pour concrete: Prepare the concrete mixture on-site and pour it into the forms. Use a concrete vibrator to avoid air bubbles.
4. Smooth and level: Use a screed board to smooth the surface as it dries. Periodically check that the walls are drying plumb and level, making adjustments as needed.
5. Curing and drying: Allow the concrete to cure and dry. Maintain proper moisture levels to prevent cracking.
6. Remove forms: Once the concrete is dry, carefully remove the forms.

Alternatively, you can build a block foundation using concrete masonry units (CMUs) or cinder blocks for the walls. You can set these hollow blocks on top of your footings, mortar them into place, and reinforce them with rebar and concrete grout.

Pour the Foundation

Once the foundation walls are in place, pour a slab foundation if your project calls for one.

Mix and Pour Concrete

Prepare the concrete mix accordingly and begin pouring it inside the perimeter of the foundation walls. Use a concrete vibrator during the pouring process.

Smooth and Level

Use a screed board to smooth the surface as it dries. Ensure the foundation is level and make adjustments as needed.

Finishing Touches

After you’ve poured and leveled the concrete, apply any finishing touches. These may include troweling the surface for a smooth finish or lightly sweeping it with a broom to add texture.

Curing and Drying

Allow the concrete to cure and dry. Maintain proper moisture levels to prevent cracks in the foundation.

Backfill and Complete Project

After the foundation has cured and passed inspections, backfill the surrounding soil. Then, you can complete your construction project.

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Proper Drainage and Moisture Control of Foundations

Effective drainage will help maintain your foundation’s integrity. Here are two methods to manage drainage and moisture:

Applying Waterproof Membranes

Apply a high-quality waterproof membrane to the foundation walls’ exterior. This barrier prevents moisture from seeping through the concrete and into your living space.

Installing French Drains

French drains help divert water away from the foundation. Install these perforated pipes around the foundation’s perimeter, sloping them away from the structure to channel water to a safe discharge point.

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Common Challenges in Foundation Construction

Be prepared to handle these potential issues as you construct your foundation:

Addressing Groundwater Issues

High water tables can complicate foundation construction. Consider the following solutions:

• Adjust your foundation design for hydrostatic pressure.
• Install a sump pump system.
• Use waterproof concrete additives.

Dealing With Poor Soil Conditions

If soil tests reveal unstable ground, here are a few solutions:

• Add a layer of compacted gravel.
• Replace the soil.
• Use deeper footings to reach more stable soil layers.

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Maintenance and Inspection of Foundations

Regularly inspecting your foundation can help maintain its longevity.

Regular Inspection Checklist

Conduct annual inspections and check for the following:

• Cracks in walls or floors
• Doors or windows that stick
• Signs of water intrusion
• Uneven settling or tilting

Signs of Foundation Problems

Watch out for the following warning signs that signify extensive foundation problems:

• Bowing or bulging walls
• Gaps between walls and ceilings
• Large cracks (wider than 1/4 inch)
• Sloping floors

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DIY vs. Professional Foundation Pouring

Laying your own foundation is possible but risky, especially if you’ve never done it before. You might be able to do it if you’ve worked with concrete and completed similar projects.

Consider the job’s difficulty level when deciding whether to hire a professional. Laying the foundation for a small shed may be easy to DIY, but laying the foundation for an entire home is a complex project with much higher stakes.

The main benefit of DIY projects is the potential for cost savings. Labor costs to build a foundation make up 40–60% of the total cost. Most homeowners pay between $5,100* and $19,400 for foundation pouring. For the average $9,100 project, you could shave $3,640–$5,460 off the price by doing the work yourself.

Remember to factor in additional expenses that could offset those savings, such as the following:

• Buying or renting equipment to level the property, dig the footings, and mix the concrete
• Consulting a structural engineer
• Obtaining multiple permits
• Setting aside time for the project

Hiring a professional foundation contractor might seem pricier upfront, but it guarantees higher quality, faster completion, and peace of mind. The structural problems caused by a faulty foundation can be costly and difficult to fix. The cost of repairing your foundation could be more expensive in the long run than hiring an experienced contractor to pour the foundation. Look for a contractor who is properly licensed and insured and backs their work with a warranty.

*Cost data sourced from contractor estimates used by Angi.

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Our Conclusion

Laying a foundation is a complex process that requires careful planning, precise execution, and adherence to local building codes. While DIY foundation work is possible for small projects, we recommend hiring a professional foundation contractor for larger structures. The foundation’s integrity directly impacts the entire building’s safety and longevity. A contractor’s expertise ensures your foundation will last, providing a solid base for your home or addition. Regular inspections and prompt attention to any issues will help maintain your foundation’s strength and stability over time.

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FAQ About How To Lay a Foundation

How do you prepare the ground for a foundation?

To prepare the ground for a foundation, start by clearing the area of vegetation, debris, and unstable soil. Compact the exposed soil and add several inches of gravel as needed to create a flat and stable base. Be sure to excavate below the frost line and plan for proper drainage.

How deep do concrete foundations need to be?

How deep a concrete foundation needs to be depends on the soil type, frost line, and building size. A concrete foundation may only need to be 12 inches deep for a small structure in a warmer climate, while the footings for residential homes typically need to be at least 18–24 inches deep. Consult the minimum depth requirements set by your local building department.

What is a footing?

A footing is a structural component found at a building’s base. Its primary purpose is to support the building’s foundation and distribute its weight evenly across the soil. Footing types include shallow footings, pad footings, strip footings, raft footings, and pile footings.

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