I’ve always wanted to build my own house, but one of the main reasons I never did was because I wasn’t sure about excavating a basement myself. I eventually decided that if I were to build the house, I’d have to get someone to excavate the basement for me, but then the big question was how much does it cost to dig a basement?
The cost to dig a basement is around $50 per cubic foot, although that figure can vary widely depending on various factors. Soil with large boulders or hardpan – extremely dense clay – can increase costs. If the land is not already cleared, then expect the price per cubic foot to be higher.
In this article, we’ll break down the costs associated with excavating a basement. You’ll also get a better idea of how contractors price out excavating, so when the time comes for you to dig, there are no surprises.
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Basement Excavation: What are the Cost Factors?
Excavating a basement for a house depends on many factors. While $50 per cubic yard of earth is an average cost, it could be less or much more depending on the landscape of the area being excavated.
The size of the basement is the number one factor. Are you excavating for the basement of a mansion, or is it a simple bungalow? What will you do with the earth being removed? Do you need it for landscaping? All of these questions will help determine the price of your basement excavation.
Contractors will add excavating costs to the price per cubic yard, so while one basement excavation might cost $50 a cubic yard, another might be $200. Let’s take a closer look at the cost factors affecting a basement excavation:
Soil Type
What kind of soil will you be digging up? Soils such as sand, silt, or loam are the easiest to remove as they are typically light and loose. In addition, an excavator operator will be able to work more quickly in these types of soils, which reduces your cost.
If you have large boulders or hardpan – extremely compacted clay – then it becomes more difficult to excavate. If the boulders are too large, then the contractor may need to bring in another (larger) machine, which will be a significant extra cost.
Fill Removal
What will happen to the fill once it is removed? If you don’t need it, then it needs to be hauled away by a dump truck. Your excavating contractor will assume a dump truck is required, which is factored into the average price mentioned above.
However, some basement excavations re-use the fill to backfill once the basement is built. Others may use the extra fill as “cut and fill”, which is the process of excavating one area of land and filling another to provide better drainage.
Cutting and filling with your basement fill could result in added cost if there is a lot of grading to do. However, if the contractor is simply re-using all the fill to backfill and spreading the extra out, then this may reduce your cubic yard cost as no dump truck or cutting and filling is needed.
Grading
If your lot needs significant grading, then this is more time the excavator operator has to spend on his or her machine. More machine time equals more cost, and expect that $50 cubic yard average to rise.
Basements built on hillsides or in dips in the landscape will require more grading than those that are already above grade.
Land Clearing
When it comes time to excavate for a basement, it is most common for the lot to be already cleared of trees and other impediments. However, if the lot is not cleared and has many trees and other obstacles, you will have to pay extra to have the lot prepped for excavation.
If there are huge trees that need to come down, you’ll need a tree service to remove them. This can cost anywhere from $500 to $10,000 or more if there are many trees or a few that are very tall.
For a lot that isn’t cleared, but has bush, then the excavating contractor can handle it and may only add an extra few hundred dollars onto the bill.
Basement Depth
A standard 8’ basement is often not 8’ deep into the ground. For anyone wanting a finished basement, you’ll need to have basement windows that you can theoretically escape from in an emergency. That means you’ll need to have at least 30” of the basement above grade, if not more.
However, to fit basement footings and a concrete slab, an excavator may need to dig 8’ – or more. Deeper excavations mean more cubic yards of earth, which means a greater cost.
Size of basement
The size of your basement is the single most important factor in determining the cost of digging out your basement. If your home is very large, you can expect to pay exponentially more for excavating as the grading and hauling will cost more, too.
Below, we’ll go over an example of how much a 1000 square foot basement excavation might cost.
Average Cost Of Digging A Basement
Let’s consider an example. We’ll calculate for a basement that has 1000 square feet and is uniformly 6’ deep. To find the cubic yards, we’ll convert each measurement into yards, meaning we’ll divide each number by 3.
For a home that will be 40’x25’, that gives us a basement of roughly 13.3 yards long by 8.3 yards wide by 2 yards deep. We multiply that number together and get roughly 222 cubic yards of earth to be removed.
Multiplying 222 cubic yards by 50 is just above $10,000 to excavate a 1000 square foot basement to a depth of 6’.
Very few lots are completely level. It is very likely that if you want a similar-sized basement, you will not have a uniform depth. Some parts might be 6’, but other parts may only be 4’ or less – or more.
Cost to Dig a Basement – New Construction
The cost to dig a new basement for a new home is around $50 per cubic foot of earth removed. This includes grading and hauling away extra fill, if necessary.
If a home is being built entirely by a contractor – meaning you are not doing any part of it yourself – then the cost may be substantially cheaper. A contractor will have access to machines and likely do the excavation at cost.
When you simply hire someone or a company out to just excavate, then you are paying for their costs plus labor, which will make the bill far greater.
Can You Dig an Existing Basement Deeper?
Yes, you can dig your existing basement deeper. This process is known as “underpinning”, and involves removing the old concrete floor, digging it out from the inside, then digging beneath the old concrete footings to add supports. When this is done, a new floor and walls are poured beneath the old footings.
Another, less invasive and quicker option is called “benching. Instead of pouring a new foundation wall beneath the old foundation, the new wall is poured within the interior rim of the old footing and slopes up to 18”.
This process isn’t as desirable as it creates an interior “bench” around the perimeter of your basement, causing you to lose valuable square footage. It is, however, much more affordable.
Benefits to Digging a Basement Deeper
There are many benefits to building a basement deeper. It is a very big job, but sometimes it is the only option a homeowner has for adding space to their house. If you live in an area with limited space and a high cost of living, digging out a basement – underpinning – is a great option to expand your home.
Here are some of the benefits of underpinning:
- Increased space
- Fewer building code restrictions – the footprint of the home doesn’t change
- Makes an unusable space into a living space
- Option for a basement apartment
- Complete basement renovation – including waterproofing
- Some underpinning minimally affects exterior landscaping
- Allows for the option of a second entrance to the house
Do I Need Permits for Digging Basement Deeper?
You need a permit to dig a basement deeper. You will also need to have the plans signed by a structural engineer, as well. When a renovation affects the structure of the house, then you will always need a building permit.
Cost to Dig a Basement Under an Existing House
The average cost of underpinning and benching for a basement is calculated by linear foot. Thus, if you have a basement that is 40×20, then you have a total of 120 linear feet.
Underpinning costs, on average, around $350 per linear foot. Benching costs less, around $250 per linear foot.
So for our 40×20 basement, you’ll have 120 x 350 = $42,000 for basement underpinning. If you want to bench instead, you’ll spend 120 x 250 = $30,000 for basement benching.
Is It Worth Digging Out a Basement?
Yes, if you cannot build your house outward or upward due to limited space and building restrictions, it is worth it. However, it is likely only worthwhile in areas where home values are very high. Otherwise, spending $50,000 to add 700 extra square feet to your basement might be better used to find a new house with a full basement already inside.
If you live in a city with a very high cost of living – Austin, Toronto, Bay Area – then adding a liveable space below is a great option. If you can turn it into a rental, then your renovation will pay for itself in a few years. Even if you keep it for yourself, it will still be a worthwhile investment.
Excavation Cost Calculator
When determining how much it will cost you to excavate, it makes sense to use an excavation cost calculator. Using this tool will help you get a better estimate and, in turn, help you when you make phone calls to local contractors.
How Much Will My Basement Excavation Cost?
We can use our excavation cost calculator to determine the cost of excavating a 40’x20’ basement for a new build. We’ll assume a uniform depth of 5’. This gives us just over 140 cubic yards of fill to be removed.
Using our average cost of $50 for excavating a basement, we’ll multiply 150×140. So we get just over $7,000 for excavating a 40x20x5 basement space.
How Long Will It Take to Excavate a Basement?
For most basements, a skilled excavator operator can dig the hole in a day. However, the excavation won’t be complete as the second day may require another machine to push the dirt to grade.
Also, while an excavator can work quickly, there may be an issue with loading dump trucks. Often contractors will have to wait on trucks to move fill, lengthening the time the job takes.
Can Basement Excavating Remove a Hill in My Yard?
Yes, an excavator can remove part of a hill in your yard if that is where your new basement will be. Although, you’ll end up with a walkout basement, it will result in less excavation required for the contractor, lowering your price.
Can Basement Excavating Happen in Winter?
Excavation can occur in the winter, but it is not an ideal option for several reasons. First, if you live in an area that experiences freezing and thawing, plus lots of snow, then you’ll end up with a huge puddle come springtime.
If your soil is clay-based, you’ll probably have to get the excavated hole pumped out before any footings can be laid. Also, there is a chance the earth will shift come spring, altering the dimensions, including the vertical dimensions, of the basement footprint.
The best time to excavate a basement is in the spring, giving the builders the full brunt of the warm part of the year to construct the house. However, if you live in a hot area that experiences little to no winter, then you can excavate at any time.
Can I Excavate a Basement Myself?
You can excavate a basement yourself, provided you can find a machine rental place that will rent you a big enough backhoe. You’ll need a machine close to 15 tons or more to properly dig out your basement.
If the job is smaller, you may be able to get away with a 10-ton backhoe. This is one job, however, where bigger is better. The bigger the bucket on the machine, the faster the job becomes. If you are renting by the day, then speed is important.
Also, operating an excavator requires experience. If you’ve never used one before, then it will take you a few hours to get somewhat used to it. Excavation sites with lots of obstacles or other homes nearby are not good areas to learn to use a backhoe, and you should consider hiring an experienced operator instead.
Equipment and Tools Needed to Excavate a Basement
You’ll need a backhoe – at least 15 tons if the basement is 6’ deep or more. You’ll also need a truck to haul the fill away if you are not using it to backfill.
A tracked loader or skid steer that can push the earth can also grade the land. If you want to spread the earth out instead of getting a dump truck, it might be more cost-effective to rent another machine to spread the earth out in addition to the backhoe.
Conclusion
The cost of digging out a basement will vary depending on your location. Areas experiencing lots of growth will likely have higher prices, as you’ll have a harder time finding a contractor to do a single job. On the other hand, rural areas will be cheaper, often significantly cheaper.
Digging out an existing basement is becoming more common because techniques are changing, and the technology has become better.
If you want an addition but don’t want to disrupt the look or landscape of your current house, consider underpinning or benching your basement. Whatever type of excavation you choose, be prepared to get a building permit and a structural engineer.