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Rear and ground floor additions: working inside the envelope.

Building out is the simpler construction and the harder arithmetic. On most Burnaby lots the zoning envelope settles the size of a rear addition before an architect draws anything.

Last reviewed September 2026

Rear yard of a custom home at dusk with a level lawn, a stone water feature, a rock retaining wall, a concrete patio with a fire table, and the side elevation of the house at right — The rear yard of an Icon build. Every square metre of lawn here is doing work under Burnaby's 40% permeable surface rule, which is the limit a rear addition and its patio compete for.

The short answer

A rear or ground floor addition is limited by the zoning envelope, not by a maximum addition size. Burnaby Zoning Bylaw No. 14815 does not publish a cap on how big an addition may be. It publishes limits on how much of the lot may be covered by building, how much has to stay able to absorb water, and how close a wall may come to the property line. In the R1 district those are 30% lot coverage on lots over 567 square metres or 40% on lots under it, a minimum permeable surface of 40%, and 1.2 metre interior side yards. Whichever of the three runs out first is the real size of your addition.

The envelope, in numbers

Every figure below is quoted from Burnaby Zoning Bylaw No. 14815, in force 1 July 2026, R1 district, one to two units. The bylaw replaced the 1965 bylaw, so any figure from an article written before July 2026 should be re-checked before you rely on it.

Maximum lot coverage

30% on lots over 567 m² | 40% on lots under 567 m²

Buildings and every accessory structure count toward the one figure. An existing detached garage is already spending coverage the addition cannot use.

Minimum permeable surface

40%

Nearly half the lot has to stay able to absorb water. The addition footprint and the patio that follows it both draw on the same allowance.

Interior side yard setback

1.2 m each side

On a 10 m wide lot that leaves 7.6 m of buildable width before eaves and projections are counted.

Front principal building height

10 m sloping roof | 9.5 m flat roof

Rarely the binding limit on a single-storey rear addition, but it governs the moment the addition carries a second floor over it.

The rule people miss: permeable surface

Lot coverage is the limit owners check first, because it is the one that sounds like it governs building size. The 40% permeable surface requirement is the one that more often forces a redesign, and it does so late, after the addition has been drawn.

The reason is that a rear addition rarely arrives alone. It comes with a patio outside the new doors, a walkway around the side to reach it, and sometimes a relocated parking pad because the addition took the old one. Each of those is hard surface. The building footprint draws down the permeable allowance and so does everything built to serve it, which is why a design that clears lot coverage can still fail the permeable test.

The fix is usually in the landscaping rather than the addition: permeable paving, gravel instead of slab, a smaller patio. That is a cheaper change to make on paper than after a designer has laid out the rear yard around a slab that cannot be built.

What counts as an addition to the City

Burnaby's definition is broader than most owners expect. In the City's own words, any change to a building's footprint or an increase in floor area is considered an addition, and that catches expansions to accessory buildings and structures including garages, awnings, patio covers, fences, retaining walls, decks and hot tubs.

The City lists what does not need a permit: replacing fixtures, cabinets and flooring, painting the inside of your home, and minor non-structural repairs to the outside. A rear addition is none of those. It changes the footprint, which is precisely the trigger.

The application is Burnaby's Building Permit Application for Additions and Alterations to Existing Residential Buildings, which marks an Engineering Pre-Application as required and states that electrical, plumbing, gas, heating installation, sprinkler and illuminated sign permits are separate from it.

Is building out the right call?

Best for

Lots with coverage and permeable surface still unspent
Houses whose existing roof and upper floor are worth keeping untouched
Families who need to stay in the house through construction
Ground floor programs: a bigger kitchen, a main floor bedroom, a family room off the yard

Fails when

Lot coverage is already at 30% or 40%, depending on lot size
The permeable surface allowance is spent on existing driveway and patio
The yard is the reason the family bought the house
Setbacks leave a strip too narrow to be worth building on

Verify before acting

Measure existing coverage from a current survey, including every accessory building
Total the existing hard surfaces before assuming permeable capacity is available
Confirm the rear yard setback that applies to your lot, which depends on whether it abuts a lane
Check whether a tree permit is triggered, since the form asks and rear yards are where trees are

Frequently asked questions

How big can a rear addition be in Burnaby?

The size of a rear addition is set by the zoning envelope rather than by a stated maximum addition size. In Burnaby's R1 district the binding limits under Zoning Bylaw No. 14815 are lot coverage of 30% on lots over 567 square metres or 40% on lots under it, a minimum permeable surface of 40%, and interior side yard setbacks of 1.2 metres each side. Whichever of those runs out first is your real limit.

What is lot coverage and what counts toward it?

Lot coverage is the share of the lot that buildings occupy. In Burnaby's R1 district it is capped at 30% on lots over 567 square metres and 40% on lots under that size. Every building and accessory structure on the lot counts toward the one figure, so an existing detached garage or shed is already consuming coverage that a rear addition would otherwise be able to use.

Why does a larger lot get a lower coverage percentage?

Burnaby's R1 district sets 30% coverage on lots over 567 square metres and 40% on lots under it. The effect is that a big lot does not scale into a proportionally bigger house. Owners of large lots often assume they have more room to build out than they do, because the percentage they are working against drops at the same time the lot size rises.

What is the permeable surface requirement in Burnaby?

Burnaby's R1 district requires a minimum permeable surface of 40% under Zoning Bylaw No. 14815, meaning that share of the lot has to stay able to absorb water. A rear addition consumes permeable area twice over: once for the building footprint and again for the patio, walkway or parking pad that usually comes with it. This rule frequently forces a redesign of hard landscaping rather than of the addition itself.

How close to the property line can a rear addition go?

In Burnaby's R1 district the interior side yard setback is 1.2 metres on each side under Zoning Bylaw No. 14815. On a 10 metre wide lot that leaves 7.6 metres of buildable width before eaves and projections are counted. Rear yard setbacks depend on whether the rear lot line abuts a lane, so the survey rather than the district minimum gives the usable number for your lot.

Does a ground floor addition need a permit in Burnaby?

Yes. The City of Burnaby considers any change to a building's footprint or any increase in floor area to be an addition, and requires a building permit for it. The City's definition explicitly extends to expansions of accessory buildings and structures such as garages, awnings, patio covers, fences, retaining walls, decks and hot tubs, so work that feels like landscaping can still need a permit.

Does a rear addition trigger the substantial reconstruction rule?

A rear addition triggers it only when the new work is large relative to what remains. BC Housing Regulatory Bulletin No. 6 states that where an addition does not create a new unit, the 75% rule applies, and that a home is substantially reconstructed when the new portion is at least three times the size of the original structure remaining. A modest rear addition to an intact house does not usually approach that, but a large one on a small original house can.

Is a rear addition easier to live through than a second storey?

A rear addition is usually easier to live through because it leaves the existing roof, kitchen and bathrooms working while the new structure goes up beside them. The house is opened to the addition late in the sequence, once the new space is weather-tight. A second storey removes the roof over occupied rooms, which is why families more often move out for that work.

Official sources