How to add an ADU to your property
Having completed a few ADU (Accessory Dwelling Unit) conversions on my personal properties, I have discovered exactly what you need to know before you start on your own home. In this post I will share with you the key things that I’ve learned.
There are several types of ADUs that you can build, depending on your goals and your local municipal codes. The top approaches to adding an ADU include: attached ADUs such as basement suites or conversions of existing space, detached ADUs such as garden suites or garage conversions, and lastly, above garage suite additions. The cost to add an ADU to your property can range from $30,000 - $150,000, depending on the type and scope of work required.
How to choose what type of ADU is right for you
Each property is unique, and will have characteristics that favour one type of conversion over another. You should consider the complexity of construction, cost implications, privacy required, and your personal goals to determine what will work best in your case.
Here is a summary of the pros and cons to each type:
| Type | Advantages | Disadvantages | Cost |
|---|---|---|---|
| Basement Suite | > Maximize existing household space > Utilities are already available within primary unit |
> Below grade living quarters may not be ideal > Sound / noise transfer |
$50-125k |
| Backyard Suite | > Completely separated suite > Best privacy > Great for short term rentals / AirBNB |
> High cost to build completely new structure > Utilities must be run to new structure > Square footage may be limited |
$100-200k |
| Garage Conversion | > Easy to build out undeveloped space, especially if attached to primary unit | > Sacrifice parking which may be required to meet code requirements > Concrete slab may require additional moisture protection |
$50-125k |
| Above Garage Suite | > Building upwards maximizes use of land > Foundation and some utilities may be in place > Space is separated from primary residence |
> Neighbour privacy is reduced > Utilities can be difficult to run |
$50-150k |
| Existing Space Conversion | > Can be done inexpensively if services co-exist on shared walls | > Sacrifice natural flow of house > Sound / noise transfer |
$10-75k |
Code requirements that you must consider for your ADU
It is absolutely critical to ensure you know the specific requirements within your municipality, and have your property permitted and inspected by a codes officer to ensure you meet all safety related codes. We always recommend having your ADU permitted and approved by your municipality. Here are a few of the big areas they typically require:
Fire safety: often there will be requirements with carbon monoxide and fire detectors. Where I live in Calgary, every bedroom must have a detector, as well as common areas. In addition, they must be interconnected with other detectors in the property. Depending on your area, there may also be specific drywall and sprinkler system requirements.
Windows: if building below grade, you will certainly be required to ensure that windows meet egress requirements. It’s also nice to use large windows if building in a basement to help with natural light.
Entryways: a separated entrance is ideal, however most areas dictate additional items like doorway sizes, use of handrails, and landing size minimums.
Parking: your area may require off-street parking, such as in a back lane pad or garage. This helps keep street parking availability for neighbours that will be impacted.
Heating: a secondary heating source is often required. The best choice may vary depending on your climate. Here in Canada, a secondary natural gas furnace is usually the ideal choice for it’s economics long term. However, the upfront cost is higher.
Plumbing: ADUs usually have to be protected with backflow valves, on the branch drain lines.
Don’t consider this an exhaustive list - each city, town and municipality will have their own list of requirements. Make sure you find out the specifics in your area!
Beyond the code
Beyond meeting the code requirements, there are a few other considerations you might want to make.
Laundry: if possible, can you add a dedicate in-suite laundry? The plumbing and electrical work are added expenses, however add significant value to a tenant.
Full vs partial kitchen: are you able to add full size appliances, instead of hot plate areas? A full size kitchen will maximize the rentability of your ADU.
Sound proofing: when sharing walls with tenants, it is important to include sound proofing in your planning. I always include Roxul Safe n’ Sound, resilient channel, and 1/2” drywall on shared walls / ceilings.
Hot water supply: if sharing a hot water heater, it may be a good idea to upgrade to an oversized hot water tank, or convert to a tankless on-demand hot water supply.
Storage: this is especially important for long term rentals, where storage may come at a premium. Include in-suite storage areas as well as garage or shed storage. In small suites, finding a place to park that bicycle or Christmas tree can be challenging, so keep that in mind!
Is an ADU for you?
Now that you know what is involved, do you think an ADU will work on your property? If so, which type fits best? I’d love to hear your thoughts in the comments!
Related post: Is renting out your basement right for you? (what no one tells you!)