Explainer

Duplexes, Triplexes, and the Homes in Between: A Plain-Language Guide

A duplex, a triplex, a fourplex, a townhome. If those words sound like planning jargon, here’s the plain version: they’re just names for how many households live on one lot, and Flathead Valley cities are changing their rules to allow more of them. This guide walks through each home type, what it actually looks like on a street, and why allowing more of them inside existing neighborhoods matters for the workers and families trying to stay in Columbia Falls, Kalispell, and Whitefish.

The problem these home types solve

Housing costs in the Flathead Valley have climbed faster than local wages: teachers commuting from an hour away, service and retail workers doubling up in a single rental, families who grew up here priced out of buying anywhere near their own parents. Part of the reason is simple supply and demand. For decades, most residential land in Flathead Valley cities allowed exactly one thing to be built: a single detached house on its own lot. That’s the most expensive way to use a piece of land, and it leaves no other option for someone who needs something smaller or more affordable.

The home types below aren’t new inventions. They’re the kind of housing that existed in most American towns, including in the Flathead Valley, before zoning rules made them illegal to build almost everywhere. Bringing them back means allowing the range of homes that already exist on plenty of streets in Whitefish, Kalispell, and Columbia Falls to be built again.

The home types, explained

Duplex. Two homes on one lot, side by side or stacked, each with its own entrance. From the street, a well-built duplex is often indistinguishable from a large single house. It’s a common way for a local property owner to add a rental home or house a family member.

Triplex and fourplex. The same idea with three or four homes instead of two, typically built to look like a slightly larger house, not an apartment complex, and still fitting on a standard residential lot.

Townhome. A row of homes that share side walls but each have their own front door, small yard or patio, and often their own garage. Townhomes hold more households on a block while keeping every home at ground level, which makes them a common choice for families and first-time buyers.

Courtyard apartment. A small cluster of homes, often six to twelve, arranged around a shared central courtyard instead of a hallway. This layout keeps buildings low, usually two or three stories, with a shared outdoor space that functions like a shared yard.

Cottage court. A group of small, detached homes arranged around a shared central yard, with parking tucked to the side or rear. Each home looks and feels like its own little house, and cottage courts are one of the most naturally affordable versions of this housing type because each individual home is small.

Taken together, these are sometimes called “missing middle” housing in planning circles, a shorthand for the range of home types missing between a single detached house and a large apartment building. You’ll see the term on zoning maps and in city planning documents, but what it means in practice is simple: more shapes and sizes of homes, built at a scale that fits into an existing neighborhood.

Why this helps Flathead Valley families

More home choices in convenient, connected communities means options at more price points, in the places people already want to live: close to Main Street, close to schools, close to the jobs that keep Columbia Falls, Kalispell, and Whitefish running. A duplex or townhome costs less to build per home than a single detached house on its own lot, because the land, utility connections, and site work are shared. That lower cost can translate into a more attainable price for a working family, without changing the height or footprint of what’s built.

These home types also mean growth doesn’t have to come at the expense of the farmland and open space that ring the valley. Every home added inside an existing neighborhood is one less home pushing a new subdivision onto the edge of town: sprawl that eats agricultural land and adds to traffic congestion, or more home choices tucked into neighborhoods that already have the roads, water lines, and schools in place.

Local homebuilders and property owners are often the ones best positioned to build this kind of housing, at a scale that doesn’t require outside capital or a large-scale project.

What’s changing locally

All three Flathead Valley cities are updating their zoning codes to allow more of these home types on lots where only a single detached house was previously permitted, part of a broader set of state housing law changes reshaping what’s legal to build. Read our plain-language guide to the state law driving these changes and see what each city’s updated land use plan means for your neighborhood. Whitefish, Kalispell, and Columbia Falls each have specifics worth checking if you own property or are watching a project near you.

The bottom line

A duplex, a triplex, a townhome, a cottage court: these aren’t a departure from what the Flathead Valley has always had. They’re a return to a wider range of home types that used to be normal here, sized and scaled to fit into the neighborhoods that already exist. Allowing more of them is one of the more direct ways to help the teachers, childcare workers, retail employees, and young families who keep this valley running find somewhere to live in it.

Want to follow these changes as they happen? The Flathead Valley Land Use Planning Brief tracks zoning and housing decisions in Columbia Falls, Kalispell, and Whitefish every week. Subscribe to stay informed on what’s changing near you.