How Much Does It Cost To Build A Basement Or Foundation?

Foundation Cost

A typical 1,200-square-foot house foundation costs $6,900 to $16,200 for a concrete slab, or about $40,000 for a full basement (unfinished). A floating slab for a mobile home runs $4,600 to $14,000, while a standard 24’ x 24’ (2-car) garage foundation costs $3,100 to $4,800.

Average Foundation Cost

National Average Cost	$9,260
Minimum Cost	$4,600
Maximum Cost	$26,750
Average Range	$5,128 to $19,350

The main types of foundations are slab-on-grade, which is the most common and least expensive; a crawl space foundation that has short walls, pier and beam, or a full basement foundation with 8’-10’ walls for living or storage.

Cost of Foundations By Type

Foundation Type	Average Cost Per Square Foot	Average Total Cost
Monolithic Concrete Slab	$5	$4,600 – $20,000
Stem Wall Concrete Slab	$6	$7,000 – $20,000
Pier and Beam	$9	$7,200 – $13,500
Crawl Space	$13	$10,300 – $19,400
Basement	$33	$26,800 – $50,300

A correctly installed foundation holds the weight and load of the house in place, keeps moisture out, insulates against the cold, and resists the movement of the surrounding earth.

Table of Contents

1. Foundation Cost
2. Foundation Cost Calculator
• Per Square Foot
• Concrete Slab
• Pier and Beam
• Full Basement
• Crawl Space
3. Concrete Foundation Cost
• Monolithic
• Stem Wall
• Raft
• Footings
4. Basement Foundation Cost Calculator
• Excavation
• Building For New Home
• Adding To Existing House
• Daylight or Walkout Basement
• Digging & Pouring
• Poured Walls
• Block Foundation
5. Best Foundation For A House
6. Cost To Rebuild or Replace Foundation
7. Mobile Home Foundation Cost
8. Garage Foundation Cost
9. Additional Foundation Estimates
10. Hiring A Foundation Contractor
11. Foundation Contractors Near Me

Foundation Cost Calculator

Foundation installation prices include the cost of excavation, grading, and the number of footings. The type of foundation and depth dictate the cost of materials and labor. Calculating your house foundation cost depends on:

• Site and ground conditions, including local flooding, earthquake, frost heave, wind, and termite prospects.
• Design factors imposed by the buyer, lender, and local building codes.
• Construction practices.

House Foundation Cost Calculator

Square Feet	Concrete Slab	Pier and Beam	Basement (Unfinished)	Crawl Space	Raft
800	$4,609 – $10,816	$7,200	$26,811	$10,320	$6,000
1,000	$5,750 – $13,520	$9,000	$33,506	$12,920	$7,500
1,200	$6,936 – $16,224	$10,800	$40,239	$14,480	$9,000
1,500	$8,670 – $20,280	$13,500	$50,299	$19,350	$7,500
2,400	$13,872 – $32,448	$21,600	$80,478	$30,960	$12,000

Foundation Cost Per Square Foot

A foundation costs $5 to $33 per square foot depending on the type. A poured concrete slab costs between $5 and $14 per square foot, while an unfinished basement foundation averages $33 per square foot.

Foundation Cost Per Square Foot

House Foundation Types	Cost Per Square Foot
Monolithic Concrete Slab	$5 – $14
Stem Wall Concrete Slab	$5 – $6
Pier and Beam	$7 – $11
Crawl Space	$7 – $14
Raft	$5 – $10
Basement (unfinished)	$33

Concrete Slab Foundation Cost

A concrete slab foundation costs $5.75 to $13.52 per square foot, with most homeowners spending between $5,750 and $20,280. The total cost depends on the size, condition of the soil, location, and whether it's a monolithic slab, stem wall slab, or a raft foundation.

The average cost to build a 1,350-square-foot concrete slab foundation for a one-story home is $8,600. If extra footings are required, add $6.53 per square foot to the cost.

Poured Concrete Foundation Pros and Cons

Pros	Cons
This is the cheapest foundation for a home. It doesn’t require deep excavation. It doesn’t need much maintenance. Concrete doesn’t encourage bug or rodent problems. It usually doesn’t promote moisture problems, especially if a vapor barrier is installed.	It tends to shift and crack in soil with deep frost lines. Repairs can be expensive as it has to be drilled through to access plumbing pipes. You don’t gain any additional storage space. You’re working with an Inflexible floor platform.

Concrete slabs are used as foundations for houses at an average thickness of 6 inches, but also poured 4” to 8” thick for mobile homes, garages, workshops, driveways, and patios.

Pier and Beam Foundation Cost

Pier and beam foundations cost between $7 and $11 per square foot, averaging $7,200 and $13,500 total. The more uniform shape the house is, the lower the cost. When different sections of the house start projecting off from a central shape, with sloping in the site, it's more expensive.

Pier and Beam Foundation Pros and Cons

Pros	Cons
This foundation has crawl space under it, which keeps the house away from moisture and is suitable for homes in flood-prone areas. The additional space is useful for storage. Plumbing, wiring, and pipework is usually under the home, making them easy to access. This foundation is suitable for seismic areas.	The space can be moisture-rich and grow mold and mildew. Drainage systems can be expensive. Wood piers can be prone to termite damage and rot. Floors in the home are poorly insulated if there’s no insulation under the house.

• Piers – Concrete piers are drilled about 12 inches below the frost line and poured first. Piers are spaced 5 to 10 feet apart depending on the condition of the soil, the design of the home, and the weight load.
• Joists & Grade Beams – Then, wood or concrete joists are run horizontally every 12 feet along the top of the piers. Some companies use steel jack stands or masonry blocks, or even hardwood posts, rather than concrete. The foundation (whether wood or concrete) rests on the beams.

Basement Foundation Cost

Installing an unfinished basement foundation costs $33 per square foot on average, while the cost to finish a basement adds $32 and $47 per square foot. Most homeowners spend $26,000 to $80,000 to build their full basement foundation with adequate moisture prevention and drainage.

Basement Foundation Pros and Cons

Pros

Cons

Built either entirely below ground or partially above it, basement foundations give strong structural support to buildings. They work well with houses built on slopes. Homeowners gain additional living space—sometimes double the existing square footage. The living space protects against tornadoes and hurricanes. A lot more detail later in the article. The basement is cool in summer, warm in winter. Having ductwork in the basement ceiling provides easy access for utility work.

It’s expensive to build and finish out. Basements tend to flood or grow mold and mildew without preventative measures in place They can be dark.

Crawl Space Foundation Cost

A crawl space foundation costs $7 to $14 per square foot, or between $10,320 and $19,350 total. Framing a house on a crawl space foundation costs 30% more than one over slab-on-grade. Many contractors recommend building a basement over a crawl space due to the ROI on extra living or storage space.

The cost is somewhat higher than a pier and beam home due to the additional excavation costs and concrete perimeter walls, but also protects against water damage. Homeowners can install ventilation areas throughout the perimeter, or completely close off the crawl space.

Crawl Space Foundation Pros and Cons

Pros	Cons
It is a good option for houses built on slopes in hotter climates. Useful in areas prone to flooding or earthquakes. There is usually 18” – 24” of space created by the installation, which allows better access to plumbing and ductwork.	It’s labor-intensive to build. It’s not energy efficient. The rise from ground level to the front door can cause problems for the mobility impaired. Crawl spaces have moisture issues which lead to mold, mildew, rotting wood, and mosquitoes.

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Concrete Foundation Cost

The average concrete foundation costs $5,100 to $15,400, or between $6.83 and $10.32 per square foot for both materials and installation. Your final cost will depend on the size and thickness of the slab, and if you add any special reinforcement such as wire mesh or rebar.

This is the easiest and cheapest foundation for a home. One solid slab is poured for the entire house, and it doesn’t require deep excavation.

Concrete Foundation Cost

Square Feet	Pouring Labor	Materials (6" Thick)	Average Total
400	$1,040	$1,524	$2,564
500	$1,300	$1,905	$3,205
576	$1,498	$2,195	$3,692
600	$1,560	$2,286	$3,846
800	$2,080	$3,048	$5,128
1,000	$2,600	$3,810	$6,410
1,200	$3,120	$4,572	$7,692
1,500	$3,900	$5,715	$9,615
2,400	$6,240	$9,144	$15,384

Monolithic Slab Foundation Cost

A monolithic slab foundation costs $5 to $14 per square foot installed. Monolithic slab is a concrete slab that is poured once at least ½ a foot above the ground and is thicker around its perimeter. Within this category are one-way beam and two-way beam slabs.

Monolithic Slab Foundation Cost

Square Feet	One-Way Beam	Two-Way Beam
800	$7,840	$10,816
1,000	$9,800	$13,520
1,200	$11,760	$16,224
1,500	$14,700	$20,280
2,400	$23,520	$32,448

• Monolithic one-way beam – costs $9.80 per square foot on average. This type of foundation pours the beams (or footers) at the same time as the slab.
• Monolithic two-way beam – runs about $13.52 per square foot. A one-way beam supports the foundation on two edges, while the two-way beams support all four edges at the same time, providing a more stable base.

Stem Wall Foundation Cost

The cost of a stem wall foundation is $51 per linear foot installed, averaging $7,000 to $20,000 total. A 37’ x 8’ tall wall costs about $1,900 each. The cost to build a 1,350-square-foot stem wall foundation is $7,550 on average.

After the rebar is set and the footings are poured, polysteel or masonry stem walls forms are insulated with polystyrene blocks, and the stem walls are poured. All rough-in plumbing is set up, and then the concrete is pumped in using a boom pump over a compacted area filled with structural sand fill.

A stem wall foundation works well when building on a slope, as different sections can be built to different heights. The slab can be elevated to accommodate septic systems based on gravity flow. Stem walls add stability to homes and buildings in areas where earthquakes may happen, or soil may become unstable.

Average Cost of a Raft Foundation

Raft foundations cost from $5 to $10 per square foot. The cost to build a 1,350-square-foot raft foundation is an average of $10,125. Reinforcing the concrete with rebar costs an additional $1 to $2 per square foot.

Mat or raft foundations are used where there are poor ground conditions, such as soil that is unable to bear any loads. The concrete slab rests on steel-reinforced soil, columns, or walls. The load or the weight of the house is stabilized through the raft foundation and dispersed to the earth.

Labor Cost to Pour a Concrete Foundation

The total cost to pour a concrete foundation $6.41 per square foot on average. The labor cost to pour concrete is $2.60 per square foot, while the cost of concrete is $3.81 per square foot. Concrete contractors charge $45 per hour with additional concrete delivery fees of $60 or more.

To pour a 1,200-square foot foundation, $3,120 would be attributed to labor, and $4,572 in concrete costs. It typically takes three workers a full 8 hours to pour a foundation.

Concrete slab foundations for homes should be 6” thick with 3,000 PSI concrete. After the lot is graded with sand and crushed gravel, and footings are poured, one solid slab is poured for the entire house, usually inside a wooden frame filled with rebar—iron mesh—to strengthen the concrete slab and prevent cracking.

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Basement Foundation Cost Calculator

The cost to build a basement is $26,000 to $80,000. The cost to pour a basement averages $33 per square foot, which is lower than the cost of adding a room at $86 to $208 per square foot. Basement installation cost depends on excavation, grading, materials, labor, size, style, and finishing.

Basement Cost

Square Feet	Excavation	Flooring	Stem Walls	Total (Unfinished)
800	$12,000	$4,609	$10,202	$26,811
1,000	$15,000	$5,750	$12,756	$33,506
1,200	$18,000	$6,936	$15,303	$40,239
1,500	$22,500	$8,670	$19,129	$50,299
2,400	$36,000	$13,872	$30,606	$80,478

Once excavation work is complete, a typical unfinished basement is built in three steps – footings, walls, floor.

1. The footings are poured and the ground graded.
2. A drainage system is set up around the exterior of the footings to carry water away from the foundation.
3. The walls are poured into grooves cut into the footings, so they are fastened to the footings.
4. The forms are then removed, and the dirt backfilled.
5. A vapor barrier is laid.
6. The concrete floor is poured last.
7. The exterior walls are waterproofed.
8. Precast concrete steps are usually dropped in place with a crane.

Unfinished Basement Costs Per Square Foot

Item	Percent of Budget	Cost Per Square Foot
Excavation (10’ – 12’ depth)	45%	$10 – $20
Foundation Floor	17%	$5.75
Stem Walls	38%	$12.75

Basement Excavation Cost

Basement excavation costs for a foundation range from $10 to $20 per square foot, or between $1.65 to $3.31 per cubic yard. Prices can vary significantly based on the condition of the soil (light, wet, or rock), and the type of equipment used.

Basement Excavation Cost

Soil Condition	Cost Per Cubic Yard
Light Soil	$1.65 – $2.18
Moist Soil	$1.96 – $2.64
Wet Soil, Loose Rock	$2.48 – $2.69
Blasted Rock	$3.31

Basement Excavation Costs By Difficulty

Depth & Difficulty	Cost Per Square Foot
12’ – 18’ Depth	$10 – $12
Deeper Footings	$12 – $15
Difficult Soils	$15 – $20

While a basement is one of the most expensive foundations to build, it’s the most versatile; giving additional living and storage space without the expense of a complete add-on to the home. Building a basement as part of new home construction can greatly increase the value of your home.

Building a Basement for a New Home

Basement installation for new construction costs $26,000 to $50,000 on average. Excavating at least eight feet deep then grading the land will be the most significant expense followed by materials, drainage systems, sealing, and waterproofing.

There are three main types of basements to choose from based on your specific location, soil, and groundwater conditions. Standard full basements typically have 8'-10' walls and can only be accessed from inside the house.

1. Standard Full Basement
2. Walk-out Basement
3. Daylight Basement

Daylight or Walkout Basement Cost

A typical walkout basement costs $47,000 to $100,500. A walkout basement costs about $20,000 more than a regular full basement and requires extra excavation and grading.

If your home is built on a hillside, you have the option of creating a daylight basement, which allows for full-size doors and windows that let natural light into the area through exposed walls. The cost to build a daylight basement is higher than a full basement, due to:

• More extensive underground footings.
• Higher foundation walls on the low side.
• Higher construction costs from building on a slope.
• Additional excavation.
• More site preparation on hillsides because of the complexity of working on them and getting materials to and from the site.
• Breaking the basement slab to reach the sewer line.

Finished or Unfinished Basement?

During construction, you have the option to build a finished basement for an additional $22,000 to $46,000 to make it into a livable space with rooms. If you plan to finish your basement, there are few things you can do now, at the foundation stage.

1. Dig deeper and get higher basement ceilings than the typical 8 feet in height to make room for the pipes and ductwork. Ideally, excavate to give your basement 9’ or 10’ ceilings.
2. With higher walls comes the need for thicker walls, as they need to be strong enough to safely support both the lateral load and the load above the house. Upgrading to 3,500 PSI concrete is recommended for this purpose.
3. Prevent potential moisture and soil gas problems with vapor barriers and adequate ventilation.

Cost to Add a Basement to an Existing House

The average cost to raise a house to add a basement is $40,000 to $50,000, or about $4o to $100 per square foot. Almost 20% of that amount goes toward raising the house. A structural engineer determines if the home is structurally sound enough to lift above the foundation.

There are risks in raising a house and repairs that should be factored into the total cost. A room addition may be more cost-effective (and easier on your home) than adding a basement.

Cost to Dig a Basement Under an Existing House

Square Feet	House Raising	Foundation	Total
800	$8,000 – $14,400	$26,811	$37,811
1,000	$10,000 – $18,000	$33,506	$47,506
1,200	$12,000 – $21,600	$40,239	$57,039
1,500	$15,000 – $27,000	$50,299	$71,299
2,400	$24,000 – $43,200	$80,478	$147,678

Cost of Raising A House and Building Underneath

Level	Cost Per Square Foot	Description
Level 1	$10 – $18	House elevation service only. It does not include installation of a new foundation system, reconnecting plumbing or electrical systems, or other finishing tasks.
Level 2	$30 – $60	House elevation and installation of the new foundation system.
Level 3	$60 – $90	House elevation and all elements of the architectural, engineering, and structural design tasks.

Basement Extension Foundations Cost

When building an extension, you’ll find that you might have to dig the foundation deeper than the existing foundation to match updated building codes. If your house is old, you might have to underpin the existing foundation to avoid possible structural damage from attaching the extension to it.

Cost To Dig A Basement

The cost to dig a basement for new construction is $12,000 to $36,000. Basement excavation costs $10 to $20 per square foot and takes 2 to 4 weeks to dig-out and build. Digging a basement under an existing house averages $47 per square foot because the house must be raised first.

An engineer’s survey is required before digging to make sure there are no underground utilities in place. Also, many houses built on a slab foundation have their plumbing under the slab, which has to be rerouted and pushes the price up.

If grading is required to direct water away from the house, fine grading and leveling land costs $0.40 to $2.00 per square foot. Installing a yard drainage system costs $1,000 to $4,000.

Cost To Pour A Basement

The concrete and labor cost to pour a basement depends mostly on how deep the excavation work needs to be and the condition of the soil. Homeowners report spending $14,811 to $44,478 or an average of $18.52 per square foot to pour their basement foundation and walls. A monolithic slab will cost more to pour than a regular slab because the footings have to be set in place before the pour.

Cost To Pour A Basement

Square Feet	Stem Walls	Concrete Floor	Total
800	$10,202	$4,609	$14,811
1,000	$12,753	$5,750	$18,503
1,200	$15,303	$6,936	$22,239
1,500	$19,129	$8,670	$27,799
2,400	$30,606	$13,872	$44,478

Cost of Poured Concrete Foundation Walls

Most basement and concrete foundation walls are a minimum of 8” thick. An 8-inch poured concrete wall costs $12.75 per square foot, or $1,224 poured, on average.

Ready-mix concrete costs $119 to $147 per cubic yard, and an 8-inch thick basement wall measuring 12’ x 8’ will use 2.37 cubic yards of concrete, so concrete alone costs $282 to $348 per average wall. Walls taller than 8 feet should be 10 inches thick rather than the standard 8 inches for shorter walls—to withstand the pressure of lateral soil movement.

Poured concrete foundation walls are preferable to block foundations because they are stronger, hold heat better, are more fire-resistant, and are more watertight. And although cracks can happen in any piece of concrete, a poured concrete wall is more waterproof than a block foundation, which has many seams. One of the few cons is that they must cure on-site, so water or freezing temperatures might affect the cure.

Block Foundation Cost

A block foundation costs between $7,950 and $41,600, priced at $12 to $18 per square foot. Materials alone cost $7 to $9 per square foot for walls using 8” x 16” blocks, without the footings. A concrete block wall has an exterior concrete form with reinforcing steel and filled with concrete or cement grout.

Block Foundation Cost Calculator

Item	Average Cost
Building Permit	$500 – $1,500
Excavation and Grading	$1,150 – $15,000
Forms and Finishing	$1,600 – $5,000
Concrete Reinforcement	$150 – $500
Concrete	$2,500 – $12,000
Waterproofing and Sealing	$1,900 – $6,300
Inspection	$150 – $1,300
Total	$7,950 – $41,600

Block foundations cost more than a poured foundation because of the skilled labor needed to lay the blocks, but blocks incur a big leak risk via all the seams between blocks and mortar. Mortar doesn’t last as long as the blocks and will start to chip away after 20 – 30 years. However, they can hold up more compression weight than poured walls.

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Best Foundation For A House

The best foundation for a house depends on the soil, groundwater conditions, and frost line of the ground in the area—the depth to which the groundwater in soil freezes. The foundation has to go below the frost line because freezing water expands 9% and disturbs the foundation’s structural integrity.

To choose the best type of foundation and to calculate the house foundation cost, you’ll need to know:

1. The condition of the soil on the lot.
2. How much grading and excavation work will be required.
3. How deep the footings need to go and how many are required.
4. If there are any flooding or moisture concerns.
5. How deep the foundation needs to be to go past the frost line.

Shallow vs. Deep Foundations

Home foundation construction is either considered shallow or deep. Deep foundations cost more and require additional excavation, materials, and labor.

• Shallow Foundation – A shallow foundation, slab-on-grade, or floating slab is a concrete slab that is formed from a mold set into the ground below the frost line. Shallow foundations transfer the building loads to the earth through a slab of concrete. This type of foundation is often used in warmer climates where ground freezing and thawing is less of an issue.
• Deep Foundation – A deep foundation is typically used in poor soil conditions, unlevel ground, or if the structure needs to be raised to prevent flooding. Deep foundations are constructed from steel, wood, or reinforced concrete, and require the assistance of a structural engineer.

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Cost To Rebuild or Replace Foundation

For concrete slabs, the cost to rebuild a foundation is $16 per square foot, with the average homeowner spending $20,000 to $40,000 on foundation replacement. Foundation repairs cost from $600 to repair minor cracks, up to $10,000 or more for major repairs that require hydraulic piers.

The cost of demolition of the old slab foundation runs about $21 per cubic foot, and a new typical 6" thick concrete slab costs $6.83 to $10.32 per square foot.

Cost To Rebuild A Foundation

Square Feet	Demolition	Poured Concrete and Labor	Total
800	$8,420	$4,609	$13,029
1,000	$10,525	$5,750	$16,275
1,200	$12,630	$6,936	$19,566
1,500	$15,788	$8,670	$24,458
2,400	$25,260	$13,872	$39,132

Foundation Replacement Cost Factors

• Structural Report – An engineer’s report may be required before you can begin work, which costs $750 to $1,500. The engineer will give an unbiased recommendation on the best kind of foundation replacement for the house which could end up saving you money.
• Raising the House – The cost to lift a house and replace the foundation depends on the size of the house and the numbers of stories. Expect to spend $10,000 – $40,000 to raise a house to replace the foundation with a concrete slab or piers.
• Excavation – The cost of excavation is $10 to $20 per square foot or $2.51 to $2.68 per cubic foot. Excavation may be required if the previous space for the old foundation, once demolished, isn’t deep enough. The soil will need to be moved away from the old foundation to build new forms for the new foundation.
• Rebuilding – The cost of the new foundation is the same as if you were doing new construction. A simple slab concrete foundation costs $6.41 per square foot and will be the most economical decision after paying for the house to be raised.

Replacing Different Foundation Types

• Crawl Space – Crawl space repair and cleaning costs $1,500 to $15,000 for mold removal, ventilating, insulating, and reinforcing or replacing the foundation joists. Remove and replace any wet wood, insulation, or posts. Install a new moisture barrier sheet to keep it dry.
• Pier and Beam – Replacing or stabilizing piers under your house due to shifting soil or the need for a stronger foundation, costs from $950 – $1,600 per steel pier or $1,400 to $2,100 per helical pier. A high-end repair of piers and beams will cost about $10 per square foot.
• Concrete Slab – A typical reinforced 6” slab concrete foundation costs $6.41 – $10.32 per square foot. If you need to correct drainage problems at the same time (which can often be the cause of cracks), it can cost $1,100 – $5,500.

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Average Mobile Home Foundation Cost

A permanent foundation for a mobile home costs between $3,000 to $36,000 depending on the type. A floating slab costs $4,600 to $14,000, while a crawl space runs $4,900 to $16,800. To put a basement foundation under your mobile home costs $23,000 to $36,000.

Mobile Home Foundation Cost

Foundation Type	Average Cost
Pier and Beam	$3,000 – $8,000
Floating Slab	$4,600 – $14,000
Crawl Space	$4,900 – $16,800
Basement	$23,000 – $36,000

• Pier and Beam – A pier and beam foundation for manufactured and mobile homes is common. They are secured to the sill of the foundation with a nailing strip. Ground anchors attached to the home with steel straps can help resist wind uplift, and they can be used in conjunction with stabilizer plates.
• Floating Slab – A slab foundation for a mobile home is one of the best options for colder climates. They don’t need to be measured precisely to the base of the house. Slab foundations need to be insulated around the perimeter to keep the ground under the home warmer, or they tend to shift with soil movement during frost heave. Mobile homes must be anchored to the foundation with anchors embedded in the concrete.
• Crawl Space – One of the difficulties with moving a manufactured home onto a crawl space foundation is that the foundation has to match the exact dimensions of the house. If the foundation site isn’t accessible from the street to place the home with rollers, a crane will be required, directing the chassis beams onto the installed concrete, wood, or steel piers.
• Basement – Installing a manufactured home onto a basement foundation is difficult. The outside walls of the foundation must be the exact length and width of the mobile home, and not many contractors have enough experience to do the job correctly. Part of the difficulty is attaching the shearwalls and chassis properly to the foundation system, and all the rough-ins to go under the floor must be designed before the house goes in. Foundation bolts are usually used to secure the home.

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Garage Foundation Cost

A 24’ x 24’ (2-car) garage foundation costs $3,059 to $4,787, while a 16’ x 24’ (1-car) slab costs $2,039 to $3,191 installed. Prices range from $5.31 to $8.31 per square foot for a 4” reinforced concrete slab, and $6.83 to $10.32 per square foot for a 6” slab installed.

Garage Foundation Cost

Size (4” Deep)	Square Feet	Average Cost
16’ x 24’	384	$2,039 – $3,191
20’ x 20’	400	$2,124 – $3,324
24’ x 24’	576	$3,059 – $4,787
20’ x 30’	600	$3,186 – $4,986
36’ x 24’	864	$4,587 – $7,179

You may need to have the land graded which carries a $3,000 minimum job charge. You’ll also need excavation done at $2.51 to $2.68 per cubic foot, which costs $482 to $515 for a 24 x 24 garage slab, but this should be included in the quote from your contractor.

If you’re building a garage slab right beside the home and sharing a wall, you could run into a lot of structural damage if the new slab starts to shift. An engineer can design it with expansion joints to offset this possibility.

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Additional Foundation Estimates

Below are average overall cost estimates by structure.

Foundation Estimates By Structure

Structure	Average Cost
Concrete Slab	$5,000 – $15,000
Full Basement	$26,000 – $80,000
Garage	$2,000 – $5,000
Mobile Home	$3,000 – $14,000

Cement Foundation Cost Factors

Cost factors that increase or decrease the cement foundation cost are

• Required prep work on the lot
• Grading
• Concrete thickness
• Moisture barrier
• Forms and reinforcements used
• Delivery and pouring or pumping costs
• Finishing methods

Concrete Footing Cost

Concrete footings cost $6.53 per square foot or $154 per cubic yard. Footings add $5,224 to $15,672 to the cost of the foundation, with prices growing as the footings go deeper and wider. The estimated cost for footings and a foundation is usually quoted together by contractors.

Footings must extend below the surface of the earth, deep enough to get past the unstable soil that exists in many locations. Usually, footings are poured separately from the slab, except in the case of monolithic slabs.

Cost of Pilings for Foundations

The cost of pilings for securing your foundation costs $15,000 at minimum, plus site testing, which could add $20,800. It’s expensive because of the steps involved—soil study, excavation, concrete, capping beams, rebar, design, and project management—possibly more expensive than a solid column base.

The cost of driving in the pilings can vary based on the materials used.

Cost of Pilings for Foundations

Type	Minimum Cost
Wood – Treated or Untreated	$20,000
Steel Pipe Piling	$20,000
Prestressed Concrete Piling	$28,000
Steel HP-share Piling	$20,000
Concrete-filled Steel Piling	$15,000

In the case of unstable soil, pilings are used in conjunction with piers—they go even deeper beneath the piers to provide additional security and spread the weight load of the building. Sometimes you can dig out tunnels for the pilings around piers with an auger yourself, saving the excavation costs.

Pilings are sometimes necessary when the soil is soft, and when a solid base is not available at the proper depth. Also, it may be required when constructing a building near the seashore or riverbed.

Planning and Permit Prices

Some cities will charge $30 to $150 flat fee for your permit, while in other cities, building permits are generally figured as a percentage of the total job averaging $500 to $1,500. Your contractor should take care of the permits.

Building a foundation will always require a permit, but if you’re adding an extension or building a house, the permit for the entire project will cover the foundation.

Cost of Building Permits

Total Price of Job	Price of Building Permit
$500 – $2,000	$79
$2,000 – $25,000	$143
$25,000 – $50,000	$787
$50,000 – $100,000	$1,292

Foundation Inspections

Foundation inspections cost about $145 an hour, with most homeowners spending $150 to $1,300 total. Inspections verify that the new foundation meets all code requirements and will support the weight of your home.

The inspections will take place before you pour concrete and after the work is done. The pre-work inspection should take about 90 minutes, and you will receive a written report which will outline any changes that must take place before pouring.

Drainage and Radiant Heat

When installing a new concrete foundation, there are things you can do now that will be more difficult, if not impossible, to do after the foundation is poured.

Radiant heat adds $3 per square foot with most homeowners paying $4,800 to $10,000 on average. Drainage systems such as French drains and sump pumps cost between $2,500 and $12,000 to install.

Foundation Drainage and Heating Systems

System	Average Cost
French Drain System	$6,000 – $12,000
Sump Pump	$500 – $1,200
Sump Pump System	$2,500 – $5,500
Radiant Heat	$16 – $26/SF

• French drains are installed around the foundation to drain water away from the house. The drained water is often directed to the sump pump, which forces the water away from the house. It’s easy to install while the house is under construction, but much more expensive to connect to an existing home.
• If your basement might be prone to water problems, a sump pump can help alleviate that.
• Radiant heat is a luxury item where all pipes need to be laid under the foundation, and the concrete is poured over them. You cannot install radiant heat under a concrete foundation at a later date. If you miss the boat, another option is to place it under your flooring.
• To provide better protection against moisture issues, install a gutter system, and invest a lot in the grading of the land before work begins.

Foundation Insulation

Foundation installation costs about $2,000 on average. Many homeowners install skirting and vents around the crawl space or pier and beam foundation to allow for proper airflow, preventing moisture, and keeping critters out. Otherwise, they install a vapor/moisture barrier and dehumidifier. Homeowners who want more insulation under the floor will add spray foam, foam board, or batts between or across the bottom of the joists.

Cost To Seal Concrete

The cost to seal a concrete foundation professionally with an acrylic spray-on cure and seal will cost about $0.53 per square foot. Contractors typically charge a minimum fee of $100 to $200 regardless of project size and add 50% more to your total cost if two coats are required.

DIY costs range from $0.20 to $0.75 per square foot. Some decorative sealers will need to be reapplied every few years, while a penetrating sealer will need to be applied every 5 – 10 years.

The main reason you’ll want to seal your concrete is to keep water from eroding it and causing cracking. The cracks enlarge, and the water carries damaging salts and chlorides to the metal reinforcements damaging them as well. Applying a sealer will densify the concrete, giving it years of additional, crack-free life.

Cost to Lay A Precast Foundation

The cost to lay a precast foundation is $11 to $13 per square foot with more than 50% of the costs coming from labor. Prefab concrete slabs are poured and cured offsite then delivered to your job site and laid down over a prepared area.

Precast foundations are used for a shed or garage, but they are not strong enough for a home foundation. The most common use for pre-poured slabs is in the form of pavers installed in patios, driveways, and courtyards.

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Hiring A Foundation Contractor

Before hiring a concrete contractor, be sure to get at least three formal bids. You want the best local contractor for the project at a price within your budget, but it's usually not a good idea to take the lowest bid without verifying the following:

• Are A/A+ rated members of the Better Business Bureau.
• Have been pouring foundations for at least five years.
• Are insured and bonded.
• Are rated highly on HomeGuide and Google and can provide references from past work.
• Include all cleanup in the quote.
• Offer exact begin and end dates.

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