Can You Build Basement Under Backyard: (7 Things You Must Know)

Can You Build Basement Under Backyard

In some areas, the soil under your backyard might be bedrock or caliche clay, but most of the time, it’s just dirt, so you can dig into it to build a basement easily. With sufficient determination, tools and time, even a problematic yard can house a basement.

Can you build a basement under your backyard? Read on, and I will explain everything you need to know to put in a new basement under your backyard.

You can build a basement under your backyard, but it takes careful planning. You can build a new underground basement with the correct tools, good designs, a crew, skills, and time. Although it’s easier if you have an existing basement to extend your new space off the existing one instead of starting from scratch, you can build a basement almost anywhere.

Build Basement Under Backyard

Before you can build a basement under your backyard, you need a lot of good information. It’s not as simple as digging a hole and framing a room.

There are many aspects to building underground, and you need to consider each one carefully.

Below is a list of 7 things to know about backyard basement builds to help you prepare for the work ahead.

1 – Is It Possible To Build A Basement Under Yard

It is possible to build a basement under your yard. However, you will need a survey and professional design work, and there are other steps to take before you can finalize any plans.

If you have an existing basement, you may want to work on extending it rather than building a completely separate, freestanding structure.

2 – Do You Need Permission To Dig A Basement

You do need permission to dig a basement. Building permits are serious business, and most city and state governments enforce them with stiff penalties and significant fines.

Plus, you could also end up paying the cost of demolition and repairs to make the area safe again.

Permits are part of the process because they help ensure that you aren’t building a death trap in your yard with no skills or oversight.

According to Home Advisor, “The national average cost of a building permit is roughly $1,380. Homeowners spend anywhere between $447 and $2,313.

Depending on which city you live in, the cost may be as high as $7,500, whereas small towns may only charge $150 for one.”

To obtain a building permit, you can buy it online or through a local permit Issue Agent.

They will assess the proposal, and the permit fee will be based on how much the job should cost.

3 – How Much Does It Cost To Build A Basement Under Backyard

Extending or finishing an existing basement can get pricey. Typically these projects cost anywhere from $7000 to over $100,000, depending on where you live and how ample the space is.

However, building from scratch will cost even more.

It will cost at least $47,000 to build a proper, waterproof, safe basement under your backyard.

The foundation alone will run $5 to $40 per square foot plus labor and equipment. A slab foundation averages $12,000. Meanwhile, poured cement will cost closer to $20,000.

Framing the basement, which is creating the structure for the walls and ceiling, is another significant portion of the expense.

The average cost for framing runs around $1200, but it ranges from $500 on the low end when you buy wood and DIY to over $2000 for large spaces and professional builders.

4 – How To Waterproof Basement Under Backyard

Waterproofing is arguably the most critical step in building a basement. If you don’t take the time to learn how to waterproof your backyard basement you will have a wet, moldy, mildewed mess on your hands.

Not only will the water ruin the foundation and walls, but the fungal growth can be toxic to humans. Black mold is no laughing matter.

The steps below are an overview of how to waterproof your basement.

  1. Excavate the dirt around the external walls. You’ll need several inches of space.
  2. Install an appropriate moisture barrier.
  3. Apply masonry waterproofing on bare floors.
  4. Fill in the excavation with gravel. Please note that you should never try to push the original dirt back into the hole as it will not drain properly.
  5. Create a footer drainage system to move water away from the basement rather than allowing it to sit and soak in.

5 – Equipment Needed To Build Basement

You will need large equipment to dig a space for a basement. Renting CAT diggers or hiring a professional crew to run the dig site is part of the process.

Similarly, you will need a cement mixer or an experienced team with a cement truck to lay the foundation.

Luckily, the tools for building and finishing are much more portable. You will also need nails, screws, and other components to work with.

I’ve collected a list together so you know everything you’ll need to frame and finish your backyard basement.

  • Chalk Line – This is for marking perfect straight lines.
  • Chisel – Chisels are for chipping wood and other materials
  • Drill – A drill puts screws in place
  • Framing Hammer – This is a large hammer used for putting nails into the frame of a house or structure.
  • Level – A level tells you if things are level. I recommend a laser level.
  • Miter Saw – Miter saws cut wood. However, they also cut precise angles.
  • Nail Gun – Nail guns are for putting nails in place quickly.
  • Plumb Bob – A Plumb Bob is a weight you put on a length of twine to check that your horizontal surfaces are straight up and down.
  • Saw Horses or A Saw Table – This will give you a place to cut wood.
  • Shop Vac – Shop Vacs are heavy-duty cleaning vacuums that can pick up large pieces and even remove water.
  • Wire Cutter/Stripper – Wire cutters and strippers do precisely what their name implies. You can cut lengths of wire or strip off the protective rubber coating to expose the wires so you can connect them.

6 – How Much Space Do You Need In Your Backyard

You want to leave about ten feet of space between any basement and the fence line as a general rule.

It’s not a question of how much space you need in your backyard, how much room you have to build a basement, and your budget.

Typical basements are at least 500 to 800 square feet, but you can build any size you want.

It’s essential to have a professional survey to know which space is useable.

Moreover, you should always check local building codes since you may need to leave more room between your basement and any property lines.

7 – How Long Does It Take To Build A Basement Under Backyard

A typical basement takes 4 to 9 weeks to build. However, the size, layout, and any special conditions, such as challenging areas of clay or rock, can affect the timeframe.

It’s important to note that the timescale above is for a professional crew, not a single DIY enthusiast.

Excavating the foundation can be as quick as about 3 days, or it can take several weeks.

In the worst-case scenario, you may need to over-dig to remove obstacles like boulders and backfill the space with better soil.

Helpful Tips To Know About Building A Basement Under Backyard

Building a basement under your backyard is a big project, but one you can certainly accomplish.

The relative difficulty goes up if you have rocky soil, bedrock, or other significant obstacles, but it is still technically possible.

Here are a few helpful tips to know about building a basement under your backyard.

  • If you live in an area with permafrost lie Alaska, putting a basement in your backyard will be more difficult. Moreover, it’s a terrible idea since basements need heat when you use them in sub-freezing weather, which means thawing the permafrost, leading to sinking and other problems.
  • It is less expensive to build up than to dig down, but an underground basement has a lot of advantages like insulation and soundproofing from the ground around the outside.
  • Always have a survey done by the utility companies before you begin digging. The last thing you want is to cut off the electricity running to your home or hit a sewer line. You’ll have to pay for repairs and then pick a new location to start over if you do.
  • People who live in an area where there’s a Home Owners Association or HOA may be subject to different rules. Unfortunately, HOA members may not have the right to build backyard basements depending on the specific regulations in your neighborhood.

Final Thoughts

Putting a basement in is always a significant undertaking, and there are numerous considerations.

It’s best to find out about the ground composition in your yard and have utility lines and pipes marked before you dig anywhere. Doing this will avoid costly mistakes.

Waterproofing is vital to prevent flooding, and you’ll also need building permits. Fortunately, you can put a basement almost anywhere with sufficient skill and the right tools.

Drew Thomas

My name is Drew Thomas and I’m the creator of Fun In the Yard, your one stop site for all your outdoor games, sports, party activities, outdoor gear, and lawn & gardening tips.

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