Alright, this is going to be pretty contraversh, but I think you should have a basement. If you have a basement, great! I’ve got no bone to pick with you today 😊 But if you don’t, can you get one? I mean really think about it. If you’re life depended on it, could you get one?
Willie E. King, Jr., the author of Building Basements: The Definitive Book About Basements, is one of the national treasures of Texas. His book made me seriously consider digging a basement under any future houses I might build, and even under my current pier-and-beam house.
Here are the reasons I think this is such a good idea:
- I live in a city that is densifying quickly. Everyone is building up and adding extra houses to the lots, which really jacks up the cool 1950s neighborhood architectural vibe. I could literally double the square footage of my house, and use lightwells to make a pleasant, cool place to hang out beneath my existing home.
- Property taxes in Texas are significant. Having paid off our house, my family’s property taxes are our largest fixed expense after food. I am told that the basement will not be taxed as livable space, even if I finish it out.
- To paraphrase Joe Rogan, every few years the sky turns into a monster and eats some of the houses. I would like to have a safe place to chill and play Uno with my kids every time it seems like that might be going down.
- I don’t mean to be a bummer, but Russia has enough nuclear weapons to hit every city in the U.S. with over 50,000 people 5 times. Now they probably can’t get them all over here, but why risk it? We seem to be in a hot war with them right now. It would be nice to have some shelter in case hotter heads prevail.
- Basement additions can be cheaper than adding square footage aboveground.
- Basements can improve home energy efficiency considerably, since the ground temperature is often closer to the desired room temperature than the outside air is.
- Basements are quiet, which makes them an awesome addition to a house in an area with lots of activity.
If someone told you that you live in an area where basements are not feasible because of water intrusion, hard ground, or whatever else, keep in mind that is probably nonsense. If you don’t believe me, let Mr. King’s book convince you.
It’s true that digging basements under slab foundations is harder than crawlspaces. It’s certainly feasible but I’m not convinced that it is a good option for most people. Before the 1960s, people generally built houses with either a basement or a crawlspace-style pier-and-beam foundation, because slab-on-grade foundations were too costly when concrete had to be mixed onsite. Because of this, many rapidly densifying cities in the U.S. have lots of old houses that are perfect for basement conversions. Basements can be added to pier-and beam houses using one of three methods:
- Lift the house on steel beams and move it out of the way while you dig the basement. This method is probably the most pleasant and ergonomically friendly. Cutting and reconnecting utilities is a surprisingly straightforward process.
- Lift the house up slightly on steel beams and leave it in place (or raise it up to provide more working space). This is still a pretty good option but requires cribwork or some other temporary means of supporting the beams.
- Underpin the house one section at a time. This is the most tedious option but is generally best for masonry houses and in places with very little working space around the house. You basically dig carefully under alternating sections of the footer and fill in stones or blocks (ideally with mortar), before doing the remaining parts of the footer. Europeans have been doing this for a very long time under stone and brick buildings that were originally built with just a cellar.
The steel beams required for the first two options are expensive, so its usually best to hire a company to provide those for a set period. If you leave the house in place, you must take care not to undermine the soil that is supporting it. As a general heuristic, maintain a soil slope of 45 degrees or less around all footers, and don’t let standing water collect near the footers.
Whether or not the house is still in place, the first step in the main phase of excavation is to cut a ramp down to the basement. This can go wherever you can fit it but is usually best in the front of the house, so you can efficiently place the soil in a roll-off bin and have it periodically hauled offsite. Once you have cut the ramp, you can begin excavating the basement area. This is best done with an excavator, but if the house is still in the way, you will probably need to use a track-mounted skid-steer because of the space constraints. The following list summarizes the rest of the construction process, assuming that radon is not a concern in your area:
- Dig down to a depth that is about a foot deeper than the desired floor level of the basement.
- Construct footers to support the load-bearing walls, according to the soil strength and the final estimated load on the footers. Typical footer dimensions are around one foot thick by two feet wide.
- After the footers have cured properly, construct the basement walls using concrete forms made of OSB and reinforced with dimensional lumber. The walls should be reinforced with rebar that is tied into the footers. Concrete blocks can also be used, but the wall will be more permeable.
- Pour the slab for the floor, including a drain around the edge and a very gentle slope to a sump that can be pumped out to keep the basement dry.
- Waterproof either the outside (preferred) or inside of the exterior basement walls.
- Insulate the exterior walls if you are in an area where this is required.
- Cut the stairs into the main floor and install windows and window wells according to egress requirements.
- Backfill the soil outside of the house, compacting it in six-inch lifts and sloping it gently away from the house to keep rainwater from entering the basement.
In conclusion, basements are totally rad, and somewhat straightforward to build. Consider adding one to the house you’re building, or to the house you live in.