Building a foundation costs an average of $8,520, with most spending between $4,262 and $13,278. Foundations' costs range between $4 and $7 per square foot depending on type: concrete, pier and beam or crawl space.
The cost of the project can differ depending on the type of foundation you install. The better educated you are about the types available to you and how to plan, the better you can work with your contractor to create the best foundation for your structure at the best price.
| Foundation Type | Average Price Per Square Foot | Average Total Cost |
|---|---|---|
| Monolithic Concrete Slab | $4 | $4,500-$12,000 |
| Stem Wall Concrete Slab | $5 | $7,000-$21,000 |
| Pier & Beam | $5 | $8,000-$15,000 |
| Crawl Space | $7 | $8,000-$21,000 |
| Basement | $18 | $10,000-$175,000 |
Most foundations are defined as deep or shallow. A shallow design is set about three feet into the soil, with concrete pads extending below the frost line, transferring load from the walls to the earth. Another type of shallow foundation is called slab-on-grade. This type transfers load to the earth through a slab of concrete.
A deep foundation is used when soil conditions are more difficult, like building on the side of a hill, or if the structure must be raised to prevent flooding. These can be made from steel, wood, or either reinforced or pre-tensioned concrete. They will sometimes penetrate the bedrock, so its a good idea to enlist the help of a structural engineer.
In most cases a deep one will be costlier than a shallow one. It requires more materials, more excavation, and more labor.
Monolithic Slab $4,500-$12,000. For a monolithic slab, concrete is poured all at once to form the main slab and the shallow footings. This makes for a fast process and lower labor costs. The ideal location for such slabs would be in a temperate climate, where there isnt much anticipation of change in the soil from freezing and thawing.
Stem Wall - $7,000-$21,000. These require more labor, excavation, and materials. The features involved are the poured concrete slab, the foundation/stem wall, and footings (concrete pads) which extend into the ground. The concrete tends to be reinforced with rebar. The walls and footings give this type a higher resistance to soil changes, making it a better choice for cold climates.
Pier and beam foundations run at about $5 per square foot, averaging $8,000-$15,000. They were the most common type of foundation to build before improvements were made with concrete technology in the 1960s. They are made up of three elements:
- Piers Short and wide supporting blocks made from concrete or other masonry materials. These are secured in the ground to hold the weight of the housing structure.
- Grade beams Made of wood or concrete, these run horizontally along the bottom of the structure.
- Piles Long and slender posts made from concrete, steel, or wood, these can be driven deeper into the ground, below piers. They are used for extra reinforcement in the soil, especially for large-scale projects or when the soil is too loose at the depth of the piers.
There are very particular reasons a person would need or want this kind of foundation. It elevates the home and creates enough space for homeowners to easily access important components, such as plumbing. The available space under them makes for easier, more affordable repairs.
Elevation also keeps the house lifted away from moisture, which is a great benefit in rainy areas. In fact, this is the ideal for building your house on stilts. Piers can also be added for extra support when repairing a sagging foundation.
If you are considering a crawl space foundation, the average cost is $7 per square foot, or approximately $8,000 to $21,000. Similar to the pier and beam style, these elevate the house and can help protect against water damage in rainy climates. Their foundation (or stem) walls extend above the ground at a minimum of 18 and support the structure. Homeowners can choose to completely close off their crawl spaces or to install ventilation areas throughout the perimeter.
While crawl spaces provide the same ease-of-access as pier and beam, they can also harbor moisture and promote mold growth. There are several ways to combat this, including insulation and vapor barriers, which should be considered when planning the project. The average cost of insulation is $1-$3 per square foot and the various styles of vapor barriers average between $0.05 and $1.50 per square foot. Some homeowners opt to install crawl space humidifiers, which can cost anywhere from $70 and $1,300.
Basement - $10,000-$175,000
Basement foundations can be the most expensive option, but they may also have the greatest return on investment. Installing an unfinished basement will cost $10-$25 per square foot, while finished basements run you between $30-$100 per square foot. This makes for significant variance in price from one project to another, beginning with a low of $10,000 and topping off at about $175,000. A basement, however, is one of the most affordable ways to add storage or living space. These are most common in cold areas, as builders already need to install the footings deep into the ground to get below the frost line.
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Since the cost can vary greatly, youll need to evaluate your unique project in order to get a ballpark figure. There are a number of factors for basement installation which demand more out of your budget. These include the price of extra materials, labor, excavation, and grading, as well as your choice of basement style and refinishing.
Building for a New Home
Installing a basement for new construction costs $18,000-$30,000, on average. Some of the most significant expenses, in the process, come from excavation and grading costs. The project usually requires an excavation eight feet deep, which will increase your labor rate, and grading is absolutely necessary to ensure the ground is level. Tree removal and soil quality factor into your excavation estimate, as well.
Materials are another major contributor to a fluctuating project budget. Cinder block walls will cost less than poured concrete, though they are less durable. Higher quality drainage systems will raise your initial estimate, but they could save you money on future repairs. Other material factors include insulation, sealers, and waterproofing.
After these initial, necessary expenses, consider the type of basement you want. First, do you want a standard or a walk-out? Walk-out spaces have an outside entrance, where standard ones can only be accessed from inside the house. If you are building into a hill, you have the opportunity of building a daylight basement that features an exposed wall or walls.
Second, do you want to leave your basement unfinished or finish it during the construction? While it can be cost-effective to finish it during initial construction, the difference of savings is minor enough that you can certainly push that project to a later date. Refinishing your basement typically run you between $6,500-$18,500.
Raising an Existing House to Add a Basement
The average cost of raising a house and adding the extra level is $30,000-$70,000. Adding a basement to an existing home can be a lucrative investment, raising your property value and likely providing a stronger and more durable foundation than before. Your overall price will depend on the type being removed, the level of excavation required, and the difficulty of raising the home. Raising a house costs an average of $5,000.
If you see signs of damage or settling, such as cracks, it is important to pursue repairs right away. Foundation repairs can fall anywhere from $450 to $11,000 with typical homeowners spending around $4,000. Issues left unresolved will not go away. Cracks will multiply, water damage will wreak havoc, and you could find yourself facing a complete overhaul.
Replacement can cost between $20,000 and $100,000. The following factors should be taken into consideration:
- Structural Report - If your foundation is failing, hiring a structural engineer to correctly assess the situation is an important step in ensuring a successful replacement. The average for that service is $500. Structural engineers can help answer some very important questions. Can your home withstand the pressures of being raised? What type and materials would work better in your environment?
- Raising the home - As mentioned previously, the cost of raising is about $5,000. The price could be significantly higher, however, depending on the condition of your home, soil, and current foundation. If these conditions are poor, it will take a lot more time and equipment to raise and excavate.
- Excavating - The national average is $3,000. Once again, type and soil conditions can greatly influence the price.
- Rebuilding - Depending on the type you choose, you could be looking at a building cost of $5,000 to $100,000.
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| Service | Low | High |
|---|---|---|
| Building Permit | $500 | $2,000 |
| Excavation and Grading | $500 | $9,000 |
| Concrete | $3,250 | $13,500 |
| Form and Finishing | $1,000 | $5,000 |
| Reinforcement | $150 | $750 |
| Sealing | $600 | $6,000 |
| Inspection | $80 | $1,300 |
| Total | $6,080 | $37,050 |
The above estimates reflect costs using basic concrete. Consider that excavation rates are tallied according to labor and equipment. The hourly rate for excavation is $100 to $245 per hour, while equipment will often be priced as a flat fee between $150 and $250. Other elements will come into play such as the type and finish you choose.
Hiring expert contractors will ensure that such factors as slopes and drainage are handled correctly. Professionals will have the right equipment for excavating your property, grading the soil, as well as pouring and finishing concrete.
On a smaller scale, you may be considering installing a garage foundation. Building a garage can fall anywhere between $6,000 to $56,000 in total, with attached garages costing less to build than detached ones. Considering that concrete slabs are $3-$5 per square foot, foundations take up $1,000-$3,000 of that cost.
Foundation building for mobile homes can cost anywhere from $1,000 to $25,000. However, when it comes to deciding which one is right for you, you may not have much choice. These days, there are specific codes to meet in different cities and states which may limit you to one kind or another. Plus, if youre installing your mobile home in a community, that community may only allow specific foundations to be built.
The most commonly accepted and used type for mobile homes is the floating slab. This is permanent and could cost between $6,000 and $15,000. It is considered one of the best options for colder climates. This style usually involves a 6 slab of concrete which is reinforced with rebar. It sits right on top of the ground and is very stable.
The common option for non-permanent foundations is the pier and beam. This type performs well in mild climates and supports the house by way of cinderblocks. When built for a mobile home, it averages about $1,000-$2,000.
For an additional $1,500, a pier and beam can be upgraded to a block and footing, which features concrete footings for extra stability.
For those who would like to install a basement foundation for their manufactured or modular home, the average is $12,000-$25,000.
Laying a foundation requires a plan. You will have to adhere to local building codes and have inspections from the city or county while you build. It is important to follow local codes and get the correct permits in advance. The average cost of a building permit, alone, is $1,300. Homeowners find themselves spending anywhere from $500 to $2,000, depending on location and size. When calculating your potential budget, consider that the average price per square foot is about $0.89.
You may need to have soil or seismic reports as well. Even though getting these reports can add to the cost, it is essential that you do this because it can save you a lot of money in the long run. Testing the soil for its safe bearing capacity can play a big part in determining which type foundation you need. This will help prevent installation delays and ensure that youre installing the best type for your home. An experienced contractor will be able to help you with this, or obtain the correct permits for you.
Having your foundation inspected is one way to save yourself from unexpected issues and expenses. Expert structural engineers are trained to spot weaknesses and potential failures. Hiring a structural engineer for an inspection could run you anywhere from $80 to $1,300, with an average of $500. Aside from location and size, a unique contributing factor in the overall cost of an inspection is the experience level of the engineer. More experienced engineers can charge a substantially higher rate than those who are new to the trade.
Factoring in radiant heat and drainage will add to your project estimate. Radiant heat for your flooring could tack on up to $3 per square foot, with typical homeowners paying between $6,000-$14,000 on average. Drainage features will add an average of $3,000 overall. Still, these features are close to impossible to install later and will add value to your home. It may well be worth the extra costs upfront.
If you plan on adding features like a filtered drainage system and radiant floor heating, planning these features in advance is necessary. Drainage pipes and radiant heat tubes are placed before pouring your concrete slab and will need to be installed during construction.
If you are building a garage or workshop space, you will need to seal your concrete slab to inhibit moisture, cold or hot air, and particulates. In general, sealing concrete will add $0.50 per square foot. This could put you within an average range of $2,000 and $6,000. Left unsealed, a foundation is vulnerable to water damage and is likely to weaken over time. Commonly, homeowners with water damage face over $3,000 in repair costs or are even forced to completely rebuild.
| Preventative | Cost Per Square Foot |
|---|---|
| Regular Performance Sealers | $0.15 - $0.25 |
| High Performance Sealers | $0.50 - $2.50 |
| Reparative | Cost Per Square Foot |
|---|---|
| Replace Concrete | $7 - $8 |
| Replace Foundation | $12 - $67 |
There are two commonly used types of sealers; floor sealers and sill sealers. The sealers are normally applied during construction to keep your garage or workshop dry and well insulated. Sill sealers use adhesive foam and the application will sit between the top of the foundation and sill plate, creating a waterproof barrier.
Typically, sealers are spray-on applications designed to prevent moisture and vapor from rising through the porous concrete. This helps strengthen concrete and prevent cracks over time. Sealers can also prevent radon gas seepage and inhibit the growth of mildew or molds. Asking your hired professional to add a sealant during construction adds relatively low cost, compared to the benefits it will give you.
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You give an average overall but absolutely no specifics. I am looking to find out approximately what is the cost per square foot for my particular project without having an on site estimate. What good is the general estimate amount. What size of job does it represent.
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How big or small is the size of these cost averages? This "estimate" is useless.
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I found the information to be good over all, One item that I found omitted in the sealer portion, was that some county areas require a "moisture barrier" between the ground, or gravel base and the concrete pour. Is this a good item to add to your "sealer" article, or was I too obtuse.?
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All we need is an 8 inch wide rectangular cement footing, About 8' by 14' , so a wooden fence can rest on the cement.
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Good overview, but I am going to need much more specific info. to build on a steep slope and to be able to cantilever part of the house over the edge.
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