Turn a Basement Into an Apartment

Many cities in the world are facing housing shortages. Inflation is eating into people’s disposable income. Converting an unused basement into an apartment may help alleviate both problems. Many jurisdictions are relaxing zoning restrictions to allow basement suites.

Reasons to Turn Your Basement Into an Apartment

There are many reasons to convert a basement into a self-contained living space.

  • Rentable Apartment. For housing permanent renters.
  • Airbnb. For occasional renters.
  • Inlaw Suite. Provide comfortable and private housing for elderly family members.
  • Guest Apartment. For long-term guests.
  • Children’s Apartment. Your son or daughter can’t–or won’t leave home but you don’t want her/him or them–if married–living with you.

Turn a Basement Into an Apartment

Step-By-Step Basement Conversion

Converting a basement into an apartment may seem to be a daunting project. It certainly requires organization and planning.

Check Local Codes

Before doing anything, get a copy of the local zoning bylaws and building codes. Basement suites may not be allowed in your area. Or the whole project can be derailed by something as simple as ceiling height in the basement.

All legal construction likely requires a permit. The work will be inspected. You can be forced to tear out anything not meeting code. There is no benefit to doing any work until the permits are issued. Your taxes will also increase because of the improvements.

Basement Apartment Budgeting

One of the big advantages of having a contractor is budgeting. A detailed quote based on a site inspection and the blueprints provides certainty of cost. If it is to be a DIY project make sure all product and subcontractor quotes are in writing. Be honest about your own abilities and what work you plan to do. Add 10% to the final number to accommodate changes and unforeseen problems.

Full basement apartment construction usually costs between $50,000.00 and $75,000.00. Some may be more. If the basement is partially finished and meets code, the cost could be less. (Make sure the existing construction passes inspection.)

Return on investment can be as high as 70% for a quality conversion. When and if you decide to sell.

Planning and Blueprints

All basement apartments should have these areas included during construction.

  • Kitchen. Likely smaller than the main floor kitchen but with sink, sufficient counter space, and electrical outlets. Installing appliances makes renting easier.
  • Bathroom. Complete 4-piece bathroom.
  • Bedroom. At least one.
  • Living Room.
  • Dining Area. Or nook.
  • Storage/Closet. As much as possible. There is no basement and usually no garage space for renters to store extra belongings.

Building permits and occupancy permits require plans. Usually blueprints. Good plans not only show where walls will be built but light locations, materials to be used like flooring, window locations and sizes, door locations and sizes, and even vapor barrier among other details.

Blueprints are a very efficient way to get quotes for materials, flooring, suspended ceiling panels, plumbing, electrical, and heating without having contractors and suppliers come to the house. Especially if it is to be a DIY project. Get 15 copies. You will be lucky to have two left when it is all done.

If you have trouble visualizing sizes on paper, chalk outlines of rooms on the concrete floor–including door swings and closets to get a feel of the final size. Don’t forget that the walls are 4 ½” thick.

Before Starting To-Do List

Before starting any construction make sure problems are not covered up.

  • Humidity. Moisture control is important in basements. A dehumidifier may be needed before, during, and after construction.
  • Leaks. Make sure there are no leaks in the basement walls or floor. Water in a finished basement is messy and expensive.
  • Mold. Mold and mildew grow on any organic product; just add water. Even insulation can get mold. Make sure that any mold is removed.
  • Pests. Basements can be home to rodents and insects. Remove them all and seal any access points.

Basement ceiling insulation and rim joist insulation are much easier to apply and more effective if installed before framing. Rigid foam boards provide foundation insulation and vapor barrier when glued to concrete walls.

Plumbing, Heating, and Electrical

The best option for an independent basement apartment is to install totally separate services. Include a washer and dryer in your planning. Depending on the home’s layout, you can add a stacking unit in the apartment bathroom for the tenant’s use and continue using the ones you have. Or plan on moving your personal laundry facilities to the main floor–if space permits. Be sure to include the costs in your budget.


The basement apartment plumbing uses existing incoming water supply and sewer pipes. Properly connected sewer lines usually handle extra wastewater without much problem. It is much like having a larger family.

Sewer lines are not always where they need to be or where they are wanted. Be prepared to break out concrete floors to install lines and then repair the floor. Many newer houses have roughed-in plumbing installed in the basement when it is built–saving a lot of time and expense during the basement conversion.

The incoming water line should be split at the source to provide reasonable pressure to both living areas. Separate manifolds and hot water sources work best. On-demand water heaters take up less space and plumbing lines than traditional hot water tanks.


Basements are almost always cooler than the upper floors. Setting the heat for main floor comfort will invariably leave the basement apartment too cool. Separate heating sources and controls enable each living space to choose its own comfort zone. Heating can be provided by a separate furnace with dedicated ducting, electric heaters, in-floor heat, or wood-burning appliances.

Keep in mind that basement floors are cold and could be a source of moisture. Most forced air furnace vents are situated in the ceilings of basements and are not effective at heating the floor. Include vapor barrier and floor insulation in your heating plans. Baseboard heaters are a better option. Or consider electrically heated carpets.

Cold clammy-feeling floors make for an uncomfortable basement apartment.


Most basements only have the minimum amount of lights and plugs that satisfied the building codes of the time. Turning the space into an apartment requires many electrical upgrades to provide convenience and to meet current building codes.

The electrical panel may need to be changed to accommodate more breakers. Or another slave panel can be added and dedicated to the basement apartment. The entire service may have to be upgraded to handle the extra load. A 100-amp service is usually considered adequate.

Access, Egress, and Light

Getting into and out of basement apartments are important considerations for privacy, safety, and convenience. Also as a means of escape in case of emergency. Natural light makes for a welcoming environment.


Most building codes require dedicated entrances to basement apartments. Existing main floor entrances can often be modified to include an entry landing with separate locking doors leading down to the basement and into the main floor living area. Make sure this is an acceptable configuration when talking to the permitting office.

A separate entrance can be made through the basement wall. This option usually involves digging down to the basement floor level, cutting out the basement wall, and installing a door. Depending on the situation you will also need a retaining wall, steps, and a concrete pad c/w a drain into the weeping tile.

Walkout basements already have doors and landscaping. Changing doors for more security and privacy is often desirable. (Sliding patio doors are difficult to operate and lock.) Modify the interior to provide an entrance separate from the living area.


Basement bedroom requirements are well-regulated. All bedroom windows must provide egress–a means of getting out of the room in case of fire and large enough to allow firefighters into the room from outside. Egress windows have size and window hardware requirements according to most building codes. And common sense.

Many–if not most–existing basement windows do not meet code. Portions of walls have to be cut out and new windows installed c/w window wells and proper drainage.

Natural Light

All basement apartments are more inviting with lots of natural light. Bilevel houses usually have large basement windows. Bungalows often have tiny 30” x 12” windows that do not open. When installing egress windows in bedrooms, consider larger windows in living areas at the same time.

Walkout basements have plenty of glass area–on one wall at least. They are often set into a hillside. This means that the bedroom windows may not meet egress and will have to be changed. Adding more windows will only make for a more pleasant environment.

Hire a Contractor or DIY

Hiring a contractor with experience in basement conversions is usually the best option–but more expensive. They take care of everything including engaging subcontractors, permitting and inspections, scheduling, cleanup, and disposal. All the work should be covered by warranties and meet codes.

Converting a basement into an apartment often taxes the abilities of DIYers. Make sure you are comfortable with all facets of being your own general contractor before proceeding down this path. Doing the job yourself will save money but requires a lot of time and organization.