Types of ADUs
Explore the different types of ADUs available—from detached backyard suites to basement conversions.
Find the perfect fit for your property.
Different Types of Accessory Dwelling Units
As housing affordability becomes a growing concern in Ontario and across Canada, many property owners are looking for creative ways to maximize space while generating additional income.
One of the most practical solutions is building an Additional Dwelling Unit (ADU).
Also known as accessory dwelling units, granny flats, or in-law suites.
These secondary suites provide flexible living space that can be used to house extended family, generate rental income, or simply expand your residential unit for future needs.
ADU Styles and Designs
In this guide, we’ll explore the different types of ADUs, their features, benefits, and how to choose the right one for your residential lot.
Moreover, we’ll also cover zoning and legal considerations for ADUs can significantly influence how you build.
Whether you’re a homeowner in Kitchener, Windsor, Ottawa, or anywhere in Ontario, this guide will help you make informed decisions about adding an ADU to your property.
Detached ADUs: Standalone Backyard Suites
Detached ADUs are independent structures built on the same property as a primary residence, but physically separated from the main house.
These units often resemble small homes or tiny houses.
They come equipped with their own kitchen, bathroom, bedroom, and separate entrance.
Common examples include coach houses, laneway houses, and granny flats.
Ideal for Housing Elderly Parents, Adult Children, or Tenants
Detached ADUs offer the highest level of privacy for both the homeowner and the occupant.
They’re ideal for housing elderly parents, adult children, or tenants.
Moreover, they can be used as a guest house or short-term rental.
However, they require enough space in your backyard and must comply with local zoning ordinances along with owner-occupancy requirements.
Providing Property Value and Stable Extra Income
Due to their standalone nature, detached ADUs generally have higher construction and permitting costs.
However, they also contribute significantly to property value and can provide stable extra income for years to come.
Attached ADUs: Built Onto the Main Home
An attached ADU is physically connected to your main residence, either as an addition to the back or side of the home or a second story built above an existing portion.
These accessory structures typically have their own living amenities, though they may share some utilities with the main house.
Accommodating Family Members
This type of ADU is ideal for property owners who want to expand their residential building without constructing an entirely new structure.
They’re often used to accommodate family members, such as aging parents or young adults.
Effectively, this allows them to live nearby while maintaining some independence.
Attached ADUs are Often More Cost-Effective
Since they share a wall or infrastructure with the main house, attached ADUs are often more cost-effective to build than detached ones.
However, they tend to offer slightly less privacy.
Moreover, they may be subject to different zoning by-laws depending on your municipality.
Interior Conversions: Basement or Garage Units
Interior ADUs, also known as internal conversions, are created by transforming existing space within your home.
This may occur in areas such as a basement apartment or garage, by converting them into a fully functioning separate unit.
Interior options makes use of your current housing stock.
Naturally, this means it is typically the most affordable way to add an ADU to your existing property.
Residential Neighborhoods and Zoning Ordinances
These units are popular in residential neighborhoods where building a new structure may not be feasible due to space constraints or zoning ordinances.
They also offer faster timelines and fewer disruptions to the surrounding property.
Interior Conversions for Multi-Person Households
While interior conversions can be ideal for multi-person households or to meet changing housing needs, privacy can be limited.
Consider soundproofing, separate entrances, and well-designed layouts to ensure a positive living experience for both parties.
Above-Garage Units and Carriage Houses
A variation of both detached and attached units, above-garage ADUs—sometimes called carriage houses—are built on top of an existing or new detached garage.
These are a great way to create an additional unit without sacrificing backyard space.
Understanding the Benefits of Above-Garage ADUs
Since they are elevated along with often being built brand-new, above-garage ADUs offer more living area and privacy than basement conversions.
This is making them perfect for use as rental units, in-law apartments, or guest houses.
Construction Costs and ADU Policies
Construction costs can be moderate to high depending on the condition of the garage and structural considerations.
Municipalities may also have specific ADU policies governing height, access, and egress.
Naturally, it’s important to check your city’s official website or consult city hall before starting your project.
Modular and Prefab ADUs
As a prefab home builder in Ontario, My Own Cottage specializes in modular or prefab ADUs.
These are a smart, fast, and cost-efficient way to add a residential unit to your property.
Moreover, our units are built off-site in a controlled environment, before being delivered and assembled on your residential lot.
Prefab Floor Plans and Exteriors
Prefab ADUs combine the benefits of new construction with reduced construction time and lower labor costs.
They are customizable with a variety of floor plans, offering the flexibility of a tiny home or a full-sized detached ADU.
Moreover, you can choose energy-efficient options, modern designs, and finishes that match your main home.
Classified as Accessory Buildings
Because they are classified as accessory buildings, they are subject to zoning ordinances and require permits.
However, their streamlined process makes them ideal for homeowners looking to quickly generate additional income or create housing for extended family.
Comparison Chart: Types of ADUs
Understanding the additional dwelling unit cost is essential for budgeting accurately and planning a financially sustainable project.
For reference, here’s a helpful breakdown of each type based on key factors and associated average costs:
| Type of ADU | Avg. Size (sq ft) | Avg. Cost (CAD) | Privacy | Permits | Build Time |
|---|---|---|---|---|---|
| Detached ADU | 400–1,200 | $150K–$300K | High | High | 6–12 months |
| Attached ADU | 300–800 | $100K–$200K | Medium | Medium | 4–8 months |
| Interior Conversion | 250–1,000 | $40K–$120K | Low–Medium | Low | 2–6 months |
| Above-Garage Unit | 400–900 | $120K–$250K | High | Medium–High | 6–9 months |
| Modular/Prefab ADU | 300–1,000 | $90K–$180K | Medium–High | Low–Medium | 2–4 months |
How to Choose the Right ADU for Your Property
Choosing the right ADU depends on your budget, lot size, local regulations, and intended use.
If your goal is to create a rental housing unit for additional income, a detached ADU or prefab ADU may offer the best return.
In contrast, if you’re looking to house family members or increase your livable space affordably, an interior conversion might be ideal.
Homeowners Seeking Affordable Housing Options
Always consult your municipality’s city council or official website for guidance.
This will provide you with key information on existent zoning by-laws, owner-occupancy requirements, and permit timelines.
Some cities also offer ADU incentives or grants for eligible homeowners seeking to contribute to affordable housing options.
ADUs and the Future of Housing in Ontario
Accessory dwelling units are more than just extra space.
Rather, they’re an opportunity to meet the growing housing needs of our communities, support multi-person households, and boost financial flexibility for homeowners.
Solutions for Your Dreamy ADU
If you’re ready to explore the best types of ADUs for your property, contact My Own Cottage today.
Let us help you build a beautiful, functional additional dwelling unit that complements your main residence and supports your future goals.
Your Trusted ADU Builder in Ontario
At My Own Cottage, we believe in building high-quality, sustainable prefab homes that meet your unique needs.
We offer a range of ADU floor plans designed for maximum comfort, functionality, and value.
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Whether you’re adding a granny flat, coach house, or modern modular ADU, our experienced team will guide you through every step of the construction process.
From design and permitting to final delivery and installation.
We’re passionate about helping Ontario property owners create flexible and affordable housing choices that enhance both lifestyle and real estate value.
To get started, book a free consultation with us or simply fill out the form below.
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