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Should I Dig Out My Basement?

Digging out your basement seems like an attractive solution to gaining more useable space in your home, but it’s complicated to do and can be quite expensive. These are a series of questions you should consider when weighing whether or not to excavate the basement in your home.

Jeff Pelletier

September 3, 2019

If you’re the owner of a small Seattle home, there’s a pretty good chance the ceiling height of your basement is around six and a half to seven feet tall. Maybe even a bit less. Why on earth all these basements were dug just shy of a normal ceiling height is a discussion for another time (and honestly, I would need to do some research to verify my suspicions), but consequently, the question on your mind might very well be, “Should I dig out my basement?”

I’ve made this very move on my own house and have worked with clients on a variety of scenarios on theirs, so I want to present to you the list of things to consider when making this decision, as there is no one-size-fits-all answer.

Ask yourself these questions before you decide to dig out your basement.

How Much Money Do I Want to Spend?

Let’s start with something that may seem obvious, but often isn’t: this is going to be expensive. There are factors that can cause it to be less expensive, but the reality is, digging under your house while holding your house up above the excavation isn’t cheap. Consider the next thoughts below to see how valuable this potential new basement space is to you.

Do I Have Room to Expand Elsewhere?

Per the point above, digging under your house isn’t cheap, so looking at other areas to expand is a smart move. Perhaps you could add another story to your house, or have available area on which to build an addition. Space that isn't in the basement is going to be cheaper to build, and inherently be sunnier and nicer (which is a reason why I advocate for finishing the basement at a high level so it doesn’t feel like a demerit to spend time there). If expanding elsewhere isn’t an option and/or you still can’t get enough space then digging down might be a good choice. It is what happened at my house, as I couldn’t go up or out and so the only option was to go down.

Is My Current Basement Wet or Dry?

If you’re building a whole new foundation wall this isn’t a huge factor, as you’ll have easy access to build a great waterproofing system, but if you’re keeping your existing foundation and creating a new foundation inside the old one you’ll have complicated issues with waterproofing that may make this not the best approach. Talk to your design professional about the best way to do this, and avoid quick and easy advice from people trying to sell you waterproofing products, in particular, the spray-on products that go on the inside of your concrete wall. They don’t work no matter what anyone tells you. Once the water is already through the concrete, it is too late.

How High Off the Ground Is My First Floor?

Now, this only applies if you do a combination of digging down and lifting your house. Old houses tend to have poor connections to the yard and if your main floor is already four feet above the ground, moving it even higher will make that connection even worse.

How Close Are My Neighbors?

Digging down is possible even when your neighbors are super close, but it will be complicated and expensive. Without having to build a shoring system to prevent your neighbor’s house from falling into yours, you need enough space to have an easy 1:1 cut (45 degrees) down. So, if you have to dig 9’ down you’d ideally want a minimum of 9’ clear on the side of your house. And, you want that space on your property or you’ll have to ask for an easement from your neighbors. This may be costly, as you may have to repair things like fences or landscaping that get impacted by the excavation. If you don’t do this, you’ll have to do a shoring system similar to the walls holding up the giant pits built for skyscrapers. Certainly feasible and common, but definitely not cheap.

Do I Have Access for Digging Equipment to Reach Under My House?

This is the one that really hit me on my house. Digging down is easiest when you can build a ramp down under your house and get a mini-digger in there to pull out the soil. So many urban homes don’t have easy access for this, and so consequently, you need a setup that has a series of conveyor belts and people with shovels. Yup, there’s no magic system for this, it is basic, time-consuming, and not cheap.

What Is the Elevation of My Sewer Line?

When I excavated my basement, I had done a scan of the side sewer to see how low I could go without a pump. Funny story (this means it isn’t funny), I set the basement elevation based on that and when we dug down, discovered the reading had been wrong and the basement was set below my existing connection to the sewer. So, I had to dig up the driveway and pay for a new sewer connection that was lower (thankfully the sewer in the street was low enough). There are pumps that can work to resolve a situation like this, but they require maintenance — so, this isn’t a deal-breaker but definitely something to consider.

Even so, digging out a basement can be worth it.

If all of these issues don’t scare you away, a basement with higher ceilings can be fantastic — and go as high as you reasonably can to make it feel great. With generous ceiling height, it’ll feel like an integral part of the house and not just a finished basement. Sometimes, it is the only way to get additional space in your house and can be well worth it.

Years later, I still get plenty of enjoyment out of this space and it ensured we could stay in our house. For us, it was worth it, but each house and person is different, so carefully consider the above when making a decision about whether or not it makes sense to dig down.