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ADU Types: Garden Suite, Laneway House, Carriage House & Secondary Suite

BC homeowners have four distinct ADU options. Each has different size limits, lot requirements, costs, and trade-offs. The right choice depends on your lot, your budget, and what you actually want the unit for.

Infographic comparing 4 ADU types in BC: Garden Suite, Laneway House, Carriage House, and Secondary Suite with sizes, costs, and lane requirements

Key Takeaways

  • ✓Laneway houses offer the most independence but require lane access and cost $300K-$500K.
  • ✓Garden suites are the best option for lots without a lane. No lane access needed.
  • ✓Secondary suites are the cheapest entry at $80K-$200K but share the main house structure.
  • ✓In Vancouver, you can have both a secondary suite and a laneway or garden suite on the same lot.

The Four ADU Types at a Glance

Garden Suite (ADU-1)

Detached unit in rear or side yard at ground level

Size

500-900 sq ft

Cost

$250K-$450K

Lane Required

No

Best For

Lots without lane access that still have rear yard space

Laneway House (ADU-2)

Detached unit facing the rear lane, typically two storeys

Size

600-900 sq ft

Cost

$300K-$500K

Lane Required

Yes

Best For

Standard Vancouver-style lots with lane access

Carriage House (ADU-3)

Unit above an existing or new garage structure

Size

400-700 sq ft

Cost

$200K-$400K

Lane Required

No

Best For

Sites where ground-level footprint is constrained

Secondary Suite

Unit within the existing main house, usually the basement

Size

400-800 sq ft

Cost

$80K-$200K

Lane Required

No

Best For

Budget-conscious owners with a suitable basement layout

Visual Comparison: How Each Type Scores

Garden Suite (ADU-1)

Construction cost

3/5

$250K-$450K

Size potential

3/5

500-900 sq ft

Independence from main house

5/5

Fully detached

Permit complexity

3/5

Moderate

Laneway House (ADU-2)

Construction cost

2/5

$300K-$500K

Size potential

4/5

600-900 sq ft, often 2 storeys

Independence from main house

5/5

Fully detached with own address

Permit complexity

3/5

Moderate-high

Carriage House (ADU-3)

Construction cost

3/5

$200K-$400K

Size potential

2/5

400-700 sq ft

Independence from main house

4/5

Detached, above garage

Permit complexity

3/5

Moderate

Secondary Suite

Construction cost

5/5

$80K-$200K

Size potential

3/5

400-800 sq ft

Independence from main house

1/5

Within main house

Permit complexity

4/5

Lowest of the four

How to Choose the Right Type

Your Situation

Lane access + full budget

Best Option

Laneway house. Maximum independence, highest rental income, strongest property value impact. This is the gold standard when your lot supports it.

Your Situation

No lane + rear yard space

Best Option

Garden suite. Detached living without lane dependency. Vancouver expanded these significantly in 2023. Some suburban municipalities are still catching up.

Your Situation

Tight footprint + existing garage

Best Option

Carriage house. Builds above your existing or new garage structure. Smaller living area but efficient use of a constrained lot. Popular in Burnaby and North Vancouver.

Your Situation

Tight budget + suitable basement

Best Option

Secondary suite. Lowest cost, fastest to complete, and the simplest permit process. The trade-off is shared structure, shared systems, and lower tenant independence.

What Most Guides Miss

Stacking ADUs

Vancouver allows a secondary suite plus a laneway or garden suite on the same lot. That means two rental units from one property. The rental math changes dramatically when you add $1,500/mo from a basement suite to $2,500/mo from a laneway house.

Future-Proofing

If your lot qualifies for a multiplex under SSMUH, the ADU you build today may become part of a larger redevelopment later. Choose a type and placement that does not block future density options on your site.

Best For

  • ✓ Homeowners comparing ADU options for the first time and wanting a clear framework.
  • ✓ Lot owners unsure whether their property supports a detached or attached ADU.
  • ✓ Families deciding between maximum independence (laneway) and minimum cost (suite).

Usually Fails When

  • ✕ The lot does not meet any municipality's minimum size or setback requirements for ADUs.
  • ✕ The homeowner picks a type based on preference without checking actual lot eligibility.
  • ✕ The budget is set before understanding the real cost range for the chosen type.

What To Verify Before Spending Money

  • → Your lot dimensions, lane access, and current zoning with your municipal planning department.
  • → Whether your city allows ADU stacking (secondary suite plus detached ADU on one lot).
  • → Setback and height requirements specific to the ADU type you are considering.

Frequently Asked Questions

Can I have both a secondary suite and a laneway house on the same lot? +
In Vancouver, yes. Since 2018, Vancouver allows both a secondary suite in the main house and a laneway house or garden suite on the same single-family lot. Other municipalities vary. Burnaby and New Westminster are expanding this option under SSMUH, but check your specific city's current rules.
What is the maximum size for a laneway house in Vancouver? +
Vancouver caps laneway houses at 900 sq ft of floor area. The exact allowable size depends on your lot width and depth. Lots narrower than 33 feet face more restrictive footprint limits. Garden suites have variable maximums depending on lot size and setbacks.
Do I need lane access to build any type of ADU? +
Only laneway houses require lane access by definition. Garden suites, carriage houses, and secondary suites do not. If your lot has no lane, a garden suite or basement secondary suite are your detached and attached options respectively.
Which ADU type adds the most property value? +
A detached laneway house or garden suite typically adds 20-30% to property value. Secondary suites add less, usually 10-15%, because buyers see them as less independent. The exact premium depends on finish quality, size, and rental income at the time of sale.

Check If Your Lot Qualifies for a Laneway House

Enter any BC address to see ADU eligibility, lot requirements, and what type of accessory dwelling makes sense for your property.