Additions

Before we get attached to a design, we run the zoning numbers. Burnaby's residential zones each carry a maximum lot coverage and a maximum floor space ratio (FSR) that limits how much built area the lot will support. An over-build on a single-storey rancher might be the simplest way to add a primary suite without consuming lot coverage; a rear extension might be cleaner architecturally but eats into the back yard and the FSR allowance. Setback rules from front, rear and side property lines bracket the buildable envelope further. We do this analysis in the first conversation, against the current bylaw, before anyone draws a single elevation.

The most consequential drawing on any addition project is the one showing how the new foundation, framing and lateral system tie into the existing house. New foundation work next to an old one has to consider differential settlement — the new footing is on undisturbed bearing, the old footing has settled in over decades. We engage a structural engineer early to design the connection: dowelled rebar between old and new foundations where appropriate, beam-and-post transitions where existing walls have to carry new loads, lateral diaphragm continuity so the addition behaves with the existing home in a seismic event. None of this is glamorous, and all of it is the difference between an addition that performs and one that telegraphs cracks at every season change.

The new portion of the home gets a current-code envelope. The existing portion has whatever envelope it was built with — often no air barrier, no continuous insulation, single-pane or early double-pane windows. Where the two meet, the air barrier has to be continuous; otherwise the new addition just becomes the place where the existing home's moisture problems concentrate. We detail the air-barrier transition explicitly: which membrane laps to which substrate, where the rainscreen cavity terminates, how the existing siding meets the new cladding. These details get drawn before framing starts, because retrofitting them at insulation rough-in is messy and expensive.

Most additions in Burnaby need a building permit, and additions that add square footage frequently need a development permit (DP) as well, depending on the zone and the scale. The DP process adds review steps and time — design review for character areas, neighbour notification in some cases, council referral on bigger projects. We've been through this enough to know which scopes will sail through and which will get tugged into a longer review. We're upfront about it before drawings are committed, because finding out at month four that the DP is going to add another six months is the kind of surprise we don't enjoy delivering.

Some additions can be built with the family still in the house. A rear extension can usually be built with the existing back wall sealed until the new shell is weather-tight, then the wall comes down in a single planned week. A second-storey add is harder — the roof has to come off, and unless we can do it in a dry stretch with tarp protection planned, the house is exposed to weather in a way nobody enjoys. On larger over-builds we often recommend the family rent for the eight to twelve weeks the upper structure is open. The conversation we want to have is honest: which scope keeps you in the house, which one is much faster if you're out, and how much that gap is worth to you.

Additions of a certain scale are treated as new construction for energy code purposes — the new portion has to meet the BC Energy Step Code level in effect at permit application, even if the existing house was built decades ago. That means the new walls, new roof, new windows and any new mechanical serving the addition all carry the current Step level's targets. On a meaningful over-build or large rear extension, we run an energy model on the new envelope from the start so the framing, sheathing and insulation strategy is designed to the target — not justified to it after the fact. Confirm the exact step requirement for your permit date with the City of Burnaby building department, since the step level has been ratcheting up.