Most small multi-unit projects are not undone by a single catastrophic mistake. They are undone by a series of small design decisions made early, cheaply, and without much thought, each of which shows up later as a real number on an invoice.
By the time you are in construction, the majority of your cost is already committed. The drawings decided it. What follows is where we most often see margin disappear on three-to-six unit projects, and what it costs to avoid.
1. The test-fit you didn’t do
The most expensive drawing in a development is the one that gets produced after the land is purchased.
A feasibility sketch, showing actual setbacks, actual height limits, actual lot coverage and actual servicing, is a small fraction of a full drawing set and it answers the only question that matters at acquisition: how many sellable or rentable units does this lot really hold?
The difference between four units and three units on a lot is rarely a design preference. It is usually the difference between a project that pencils and one that does not. It also turns on rules that changed recently, and what your lot actually allows under BC’s SSMUH rules after Bill 25 is not always what the listing says. Find out before the subject removal date, not after.
2. Unit mix chosen by spreadsheet instead of by plan
It is tempting to build the mix that maximizes theoretical revenue per square foot. But unit mix drives the structural grid, the stair count, the number of service penetrations, and the party wall layout.
Three two-bedroom units and one three-bedroom unit might pro forma slightly better than four two-bedrooms. It might also require a second stair core, an extra mechanical chase, and a roof geometry that adds weeks. Run the mix past a designer before you run it past a lender.
3. Complexity in the envelope
Every jog in a wall, every change in roof plane, and every step in the foundation costs money in three places: the framing labour, the envelope detailing, and the risk of a water ingress problem five years out.
Small multi-unit buildings reward simple, disciplined massing. A clean, well-proportioned rectangle with good materials and considered proportions reads as intentional. A complicated shape with cheap materials reads as a builder’s special, and it costs more.
Design restraint is a cost strategy, not just an aesthetic one. It is the same argument we make about designing a fourplex people actually want to live in: restraint reads as quality, and it is cheaper.
4. Servicing assumptions
The single most reliable budget surprise in small-scale multi-unit work is the service connection. The lot has a water and sewer lateral sized for a single home. You are now putting four dwelling units on it.
Upgraded connections, on-site fire flow, and stormwater management can each run into five figures. Sometimes the City requires a frontage upgrade. This does not show up on a zoning map. It shows up in a conversation with the engineering department, and that conversation should happen during due diligence.
5. Energy and code compliance as an afterthought
Step Code compliance and the Zero Carbon Step Code are not paperwork you attach at the end. They shape the wall assembly thickness, the window specification, the mechanical system, and therefore the floor plan and the ceiling heights.
Requirements vary by municipality and by building type, and they have been tightening steadily on the way to net-zero-ready construction. Design the building around the compliance path you intend to use, or you will pay to retrofit the design later.
6. Finishes specified late, or not at all
An unspecified finish is a decision that will be made by whoever is standing on site that day, under time pressure, from whatever the supplier has in stock.
That is how a project ends up with three different door hardware finishes and a tile layout nobody chose. It is also how change orders happen, and change orders in construction cost multiples of what the same decision would have cost on paper.
A complete finish schedule, resolved before the trades mobilize, is one of the cheapest forms of cost control available. It costs design hours. It saves construction weeks.
7. Permit resubmissions
Resubmissions are pure schedule loss. Weeks of carrying cost, for nothing. They almost always trace back to the same causes: an incomplete drawing set, inconsistencies between the architectural and structural drawings, or missing energy compliance documentation.
If you are carrying land at current rates, a six-week resubmission delay is a real, calculable loss. Complete drawings the first time are not an expense. They are insurance with a measurable premium. What a complete BC permit set actually includes is worth reviewing before you submit.
The pattern
Every item on this list has the same shape: a decision that is cheap to make well on paper and expensive to fix on site. Design is the lowest-leverage cost in a development budget and the highest-leverage decision in it.
Where we come in
Rexford is an architectural drafting and design studio in Chilliwack. We work with developers and builders on small-scale multi-unit projects across the Fraser Valley and the rest of BC: feasibility and test-fit work at the acquisition stage, permit-ready drawing sets, and fully resolved interior specifications so the site team is not making decisions on the fly.
If you have a site under consideration, we can tell you within a week what it holds and what it will take. Get in touch.
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