An early multifamily concept plan can show the right unit count with the wrong assumptions baked in. Wall thickness, plumbing stacks, and accessible clearances all show up eventually. Five things to pressure-test before relying on the plan for budgeting or entitlements.
Early multifamily concept plans can be deceiving.
The unit count works. The mix looks right. Corridors, stairs, and elevators all fit. Maybe the exterior is starting to take shape. On paper, the project appears to be heading in the right direction.
So decisions start getting made around it. Then reality starts showing up.
Demising walls get thicker. Plumbing stacks need space. Structural systems introduce new constraints. Mechanical distribution needs somewhere to go. Electrical closets grow. Accessible clearances prove too tight for reasonable construction tolerance.
Individually, none of these issues sounds particularly significant. But by the time they're discovered, dozens of other decisions may have been built around them.
That's when inches become expensive.
A multifamily building is a lot like a hotel: one of the best places to start is the repetitive unit.
Before developing the building around it, we want to understand what the project is actually trying to accomplish. Who is the target renter? What comparable properties are competing for them? What unit sizes and mix make sense? What are the budget expectations? If the developer has built similar projects, what worked—and what didn't?
Then we start introducing technical reality.
Walls have actual thickness. Structure occupies space. Plumbing needs somewhere to stack. Mechanical systems need distribution paths. Electrical equipment requires closets, rooms, and clearances.
An inexperienced designer may not leave enough room for those systems. An overly conservative designer may make everything bigger than it needs to be.
Both can cost the developer.
Multifamily buildings magnify small decisions through repetition.
Consider a 30-foot-deep unit that's unnecessarily oversized by 18 inches. That's 45 additional square feet.
Across 150 units, you've added 6,750 square feet of building. At a hypothetical construction cost of $250 per square foot, that's nearly $1.7 million in additional construction area.
Not because the developer added an amenity, improved the resident experience, or intentionally increased unit size to support higher rents.
Simply because a dimension wasn't challenged.
The lesson isn't that every unit should be 18 inches narrower. It's that an inch doesn't matter once on a multifamily project. It matters every time you repeat it.
One of the easiest places for an early concept to mislead is something remarkably mundane: wall thickness.
Concept plans are often drawn with generic walls. Real buildings have corridor walls, demising walls, plumbing walls, exterior assemblies, and rated construction—each with actual thickness.
Introduce those assemblies too late and suddenly you're winding your way back through an entire building trying to recover inches from units, corridors, clearances, and overall dimensions.
The goal isn't to fully design every assembly during concept planning. It's to make informed assumptions early enough that the concept reflects the building you actually intend to construct.
There is another side to the equation. Some dimensions deserve extra room.
Accessibility is a good example. Designing every required clearance precisely to the code minimum may look efficient in a computer model, but buildings aren't constructed with that same level of precision.
Where practical, we intentionally build approximately two inches of additional tolerance into critical accessible clearances.
On a recent project, a contractor framed a long corridor several inches away from the design dimension. Because tolerance had been built into the accessible clearances, the framing could remain rather than potentially requiring demolition, reframing, and a schedule impact.
Those inches weren't wasted.
They were risk tolerance.
Good planning isn't about squeezing every dimension. It's knowing where square footage is expensive—and where a couple of extra inches can protect the project.
Before relying on an early multifamily plan for budgeting, entitlements, or other major development decisions, pressure-test five things:
PRODUCT — Are the unit sizes, layouts, and mix grounded in the target renter, competitive set, budget, and development strategy?
ASSEMBLIES — Are realistic wall thicknesses and exterior assemblies reflected in the plan?
SYSTEMS — Has space been anticipated for structure, plumbing stacks, mechanical distribution, shafts, electrical equipment, and other building systems?
TOLERANCE — Is the building tight where unnecessary square footage creates cost, while maintaining reasonable tolerance where construction reality demands it?
YIELD — If any of those assumptions change, does the unit count still survive?
That last question matters.
A concept showing 150 units isn't necessarily better than one showing 148 if those 150 units only fit because walls are too thin, shafts are undersized, building systems haven't been considered, and every critical clearance is sitting at the absolute minimum.
Concept design shouldn't be construction documents. Trying to solve every detail too early defeats the purpose of the process.
But a useful concept needs enough reality baked into it that a developer can begin making informed decisions around it.
That's where early architectural planning creates leverage.
A three-inch problem discovered during concept design may require moving a line. The same three-inch problem discovered months later may affect architecture, structure, MEP, interiors, pricing, permitting, or construction.
So before relying on the unit count, ask one simple question: What assumptions are baked into this plan?
The answer may tell you more about the risk in the project than the number of units shown on the page.
Evaluating a multifamily development? Bianchi Architecture can help pressure-test the planning assumptions early—while the big decisions are still relatively easy to change.
Bring us your project. We'll bring the clarity, coordination, and a plan that fits.
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