Carriage House: What It Is, Cost & Building One as an ADU

A carriage house used to mean something specific: a two-story outbuilding where the horses and carriages lived on the ground floor and the coachman lived above. It was a status symbol, the mark of a household wealthy enough to keep a carriage and the staff to drive it.

The carriage is gone. The form survived. Swap the horses for a car and the coachman’s quarters for a rentable apartment, and a carriage house becomes the original above-garage home. Today that is an accessory dwelling unit, or ADU, governed in Colorado by the same rules as any other backyard build. This guide covers what a carriage house is, what it costs to build here and why it sits at the top of the range, how the rules treat an above-garage unit, and how to get one built.

What Is a Carriage House? From Coach House to Modern ADU

The original carriage house, also called a coach house or remise, was an outbuilding for storing horse-drawn carriages and the tack that went with them. The classic version stood one-and-a-half or two stories tall: a high ground-floor bay with wide doors for the carriage and horses, and a finished level above for the coachman. Gabled roofs, dormer windows, and tall central doors gave it a look that still reads as “carriage house” today.

When the automobile replaced the horse in the early 1900s, most carriage houses became garages. The ones in cities often gained a second life as apartments and studios. That is the modern carriage house: a finished living space over a garage. Add a kitchen, a bath, and a separate entrance, and it meets the definition of an ADU. The heritage word and the legal one point to the same building.

Carriage House vs. Garage Apartment vs. ADU

Three words, one structure, different angles. Here is the clean version.

Term	What it is	Where it sits	Legal meaning
Carriage house	The heritage term, living above a vehicle bay	Above or beside a garage	An ADU if it has a kitchen, bath, and entrance
Garage apartment	The plain modern term for the same thing	Above or attached to a garage	An ADU with the same requirements
ADU	The zoning term Colorado uses	Detached, attached, or above-garage	The only legally defined term

“Carriage house” sells the character, “garage apartment” describes the layout, and “ADU” is what your city actually permits. One distinction worth drawing: if you are finishing an existing garage rather than building new, that is a garage conversion ADU, a related but cheaper and simpler project than a new above-garage build.

Modern Carriage House Designs and Plans

Today’s carriage house plans put a one or two-car garage on the ground floor and a finished living level above, usually a studio or a one-bedroom. The heritage character is a finish layer, not the structure. A gabled or hipped roof, dormers, a cupola, and carriage-style doors (the swing-look panels that actually roll up) turn a plain two-story box into something that reads as a coach house. You can lean traditional or keep it clean and modern; the bones are the same either way. Browse layouts on the Flex Flat models page and finished builds in the gallery.

What a Carriage House Costs to Build in Colorado

Here is the honest part: an above-garage carriage house is the most expensive kind of ADU to build. A garage and the foundation under it are not designed to carry a home on top, so both have to be engineered and reinforced to hold the upper floor. A two-bedroom unit above a two-car garage in the Denver metro runs roughly $350K and up. Build it modular and each floor ships as a separate module that stacks on site, which adds transport, permitting, and joining work on top of a single-level build. A studio over a single garage costs less, but the structural reinforcement keeps any above-garage build above a comparable single-level unit.

Now the part that makes it worth the premium. You are not just buying a living unit, you are getting two things on one footprint: covered parking or workshop space below, and a full rentable home above. On a tight lot, stacking is the highest and best use of the ground you have, because the garage costs you almost no extra yard. And ADUs in Colorado tend to appraise for more than they cost to build, so the home above the garage lands on your balance sheet as an asset, not just an expense. The full Colorado ADU cost breakdown walks every line item.

Above-Garage ADU Rules in Colorado and Boulder

Because a carriage house is an ADU, HB24-1152 applies. The 2024 state law requires qualifying Colorado cities to allow at least one ADU on most single-family lots, to approve code-compliant applications administratively, and to drop owner-occupancy mandates.

Beyond the height question, the path matches building an ADU in Colorado generally. The above-garage form adds a dimension that single-level ADUs do not: height. A two-story unit runs into bulk-plane and solar-access limits, the rules that govern how tall you can build and how close to the property line, and Boulder’s ADU rules cap a market-rate detached unit at 800 sq ft. If you build modular, transport height is capped near 13 ft 6 inches per module, which is exactly why a two-story modular unit ships and stacks as two pieces. Confirm your lot’s bulk-plane envelope before you commit to a two-story design, since it can be the difference between a buildable plan and a redesign.

Financing Your Carriage House

A carriage house is financed like any ADU: a construction-to-permanent loan, a home equity line of credit, or a cash-out refinance, with some Colorado cities offsetting permit or impact fees. There is no special state grant for a backyard unit. The larger above-garage price tag just makes the financing conversation matter more, so price the structural reinforcement into your loan amount from the start rather than discovering it mid-build. Our Colorado ADU financing guide lays out the full menu of loans and programs.

Olerra Carriage-House-Style Models

Olerra builds modular Flex Flats, and its system handles the two-story, above-garage configuration a carriage house calls for. Olerra’s own sizing guide is explicit that a two-story modular ADU is possible, with each floor shipping as a module and stacking on site, and the catalog includes a garage option. Because the above-garage layout depends entirely on your lot’s bulk-plane and access, Olerra scopes it in the free property check rather than selling it off a shelf.

What you get is a Colorado-based, DOLA-certified builder, which per its CEO is the only state-approved fire-rated modular ADU in Colorado, handling design, permits, manufacturing, and the crane set under one fixed-price contract. The heritage carriage-house look comes from the Nichiha and Ceraclad fiber-cement systems and the optional roof forms, all on a steel frame rated for 165 mph wind and 105 lbs of snow. Compare the living levels on the 490 sq ft unit and 735 sq ft model, or start with a Colorado ADU builder who has built the form before.

How to Get Started

The first step is a property check that tells you whether your lot’s bulk-plane allows a two-story unit, and what an above-garage carriage house would cost on it. From there, Olerra handles the whole build from feasibility to crane set, usually about 5 to 6 months.

No mystery pricing. No guessing whether your lot can go two stories. No surprise structural costs late in the build.

→ Get your free property check and quote.

Carriage House FAQ

What is a carriage house? A carriage house is a building that originally stored horse-drawn carriages on the ground floor with living quarters above. Today it means a finished living space over a garage. With a kitchen, bath, and separate entrance, it is an accessory dwelling unit (ADU).

What is the difference between a carriage house and a garage apartment? None structurally. “Carriage house” is the heritage, design-driven term; “garage apartment” is the plain description. Both are an ADU when they include a kitchen, bath, and separate entrance.

Can you live in a carriage house full-time? Yes. With a full kitchen, a bath, a separate entrance, and a permit, a carriage house is an ADU built for permanent, year-round living.

How much does a carriage house cost to build in Colorado? It is the priciest ADU type because the garage and foundation must be engineered to carry the unit above. A two-bedroom over a two-car garage in the Denver metro runs roughly $350K and up.

Do you need a permit to build a carriage house? Yes. It is permitted as an ADU, with the added review that a two-story structure triggers for height and bulk-plane.

Can you build a two-story or above-garage ADU in Colorado? Yes. Two-story ADUs are allowed as long as they fit your lot’s bulk-plane and solar-access limits. Modular versions ship and stack as two modules because of the transport height cap.

Ready to Build Your Carriage House?

A carriage house gives you covered parking and a full rentable home on a single footprint, with the heritage look on a modern, Colorado-tough build. The next step is a property check that tells you exactly what your lot allows and what an above-garage unit would cost on it.