ADU Floor Plans & Design Ideas: Studio to 2-Bedroom

Search “ADU plans” and you will drown in floor plan PDFs. The trouble is, a PDF is not a building. To actually put one up in Colorado, that plan still needs site-specific engineering, an adaptation for our snow load and code, and a builder to construct it. Most plan shopping skips all of that and ends in a folder of drawings you cannot break ground on.

This guide works the other way around. It shows the accessory dwelling unit plans that actually get built in Colorado, studio to two-bedroom, what each layout is for, the design ideas that make a small footprint live large, and the Colorado constraints that quietly decide which plans are even possible on your lot. The worked examples are Olerra’s own models, because they are real, code-stamped plans you can build, not drawings you have to start over with.

ADU Floor Plan Basics: Sizes and Layouts

Almost every ADU floor plan is a variation on three sizes, and the size you pick sets the layout.

Studio (about 245 to 400 sq ft): one open room. A sleeping zone, a kitchenette or compact kitchen, a three-quarter bath, and a small living area, with no interior walls to speak of.
One-bedroom (about 490 to 600 sq ft): a separate bedroom, a full kitchen, a full bath, and a living-dining combo. The most-built rental layout.
Two-bedroom (about 700 to 850 sq ft): two bedrooms, a full bath, a full kitchen, living-dining, and in-unit laundry.

The art of a small plan is making the square footage feel like more than it is. The moves that do the heavy lifting: an open plan with as few walls as possible, big windows and good ceiling height to borrow light and air, and full-height storage so nothing eats the floor. A Murphy or platform bed turns a studio’s sleeping zone back into living space by day. Each size is shown as a real layout below.

Studio ADU Plans (Around 245 sq ft)

A studio plan is the most efficient ADU you can build. Everything happens in one bright room: a sleeping area, a kitchenette, a three-quarter bath, and just enough living space, usually 245 to 400 sq ft. It is the right plan for a home office, a gym or studio, a guest suite, or a teen or college kid who wants their own door.

Olerra’s 245 sq ft studio is the worked example. It starts around $89,900 and reads as a polished studio rather than a full residence, because at that size the kitchen is a kitchenette, not a full range. That matters if your goal is a code-compliant rental, where a full kitchen is required; a studio for office or guest use is the cleaner fit. If you want the studio footprint but need a full kitchen to rent it, the 490 is the better base.

One-Bedroom ADU Plans (Around 490 sq ft)

The one-bedroom is the workhorse plan: a separate bedroom, a full kitchen, a full bath, and a living-dining combo, in roughly 490 to 600 sq ft. It is the sweet spot for a long-term rental and the most common choice for an aging parent or a returning adult child, because it lives like a real home while staying single-level.

Olerra’s 490 sq ft unit starts around $159,700 and comes as a large studio or a true one-bedroom. If the plan is for a parent, this is usually where you build in the aging-ready bones; our in-law suite and granny pod guides cover that design in depth.

Two-Bedroom ADU Plans (Around 735 sq ft)

The two-bedroom is a small but complete home: two bedrooms, a full bath, a full kitchen with an island or peninsula, a living-dining combo, and in-unit laundry, around 700 to 850 sq ft. It suits a family unit, a higher-rent tenant, or true multigenerational living.

Olerra’s 735 sq ft model starts around $235,900 and publishes both a one-bed and a two-bed layout. It also sits at the largest size that ships as a single module, which keeps the install to one day. Go bigger and the unit ships in two sections that are joined on site, which adds time and cost.

Detached vs. Above-Garage vs. Conversion Layouts

The same square footage plays out differently depending on where the ADU sits.

Detached: a freestanding plan in the backyard, the classic casita. Full privacy, the most layout freedom, and the highest cost.
Above-garage: a carriage house, living stacked over a garage. It buys parking and a home on one footprint, but the two-story structure costs the most.
Conversion: a basement, attic, or garage finished into a unit, usually the cheapest path, with the layout shaped by the existing shell. Our garage conversion ADU guide covers that route.

Pick the form first, because it decides which plans are even on the table.

Designing for Colorado: The Constraints That Reshape Your Plan

Here is what national plan sites leave out: a plan that is legal and buildable in Texas can be neither in Colorado. A few local realities quietly decide your layout.

The 14-foot rule. A modular unit travels by highway, and Colorado caps a single module at 14 feet wide for routine permits. That sets a hard ceiling on room widths and on how big a single-piece unit can be, roughly 750 to 850 sq ft. Bigger plans ship and join in two sections.
Snow and roof. A Colorado roof carries up to about 105 lbs of snow load, which shapes the roof structure and pitch in ways a desert plan never has to consider.
Height and bulk-plane. A two-story or above-garage plan runs into bulk-plane and solar limits that govern how tall and how close to the property line you can build. Confirm your envelope before you fall for a two-story plan.
City caps. Boulder caps a market-rate detached unit at 800 sq ft; other Front Range cities run higher. Our Colorado ADU sizes guide has the city-by-city numbers.
Single-level for aging. If a parent will ever live there, a single-level plan ages far better than one with stairs.

The point is simple: the best ADU plan is not the prettiest one you saw online. It is the one that fits your lot, your city, and the way the unit actually gets built here.

Small-Space and Colorado-Climate Design Ideas

The constraints decide what is buildable; design ideas decide how good it feels. A handful of moves make a small Colorado ADU live far larger than its square footage.

Open plan, fewer walls. Combine the kitchen, dining, and living into one volume so the eye travels the full footprint instead of stopping at partitions.
Borrow light and height. Tall windows and a vaulted or raised ceiling trade floor area for the feeling of space. South-facing glass does double duty in Colorado, pulling free winter heat into the unit on sunny days.
Furniture that does two jobs. A Murphy bed, a sofa bed, a fold-down desk, and storage benches let one room be a bedroom by night and a living room by day, which is what makes a studio work.
Storage up the walls. Full-height cabinets and built-ins keep the floor clear, and a clear floor always reads as more room.
An entry built for snow. A small mudroom or a covered, recessed entry handles boots, coats, and Colorado winters so the living space stays clean and warm.
Indoor-outdoor in summer. A patio door onto a small deck effectively adds a room for half the year.

None of these need extra square footage. They are about spending the footprint you already have well.

How to Choose the Right Plan

Skip the square-footage-first approach. Start with what the ADU is for, and the plan follows.

A home office, gym, or guest room: a studio (245) is plenty.
A long-term rental: a one-bedroom (490) hits the best rent-to-cost ratio.
An aging parent or adult child: a single-level 490 or 735, built with in-law suite flexibility and granny pod accessibility in mind.
A family or full multigenerational unit: the two-bedroom (735).

Once the use is clear, filter by your lot and city using the constraints above, then check it against the budget. Every extra 100 sq ft adds real money, so the right plan is the smallest one that does the job. For the full numbers, see what an ADU costs in Colorado.

Where ADU Plans Actually Come From

There are three ways to get an ADU plan, and they are not equal.

City pre-approved plans. Some Colorado jurisdictions offer pre-approved ADU designs to speed permitting, and Denver’s West Denver program publishes a set of studio-to-three-bedroom plans. They are a real head start, but they still need site-specific engineering and a builder.
House-plan marketplaces. Sites sell downloadable ADU plans for a few hundred dollars. You own a drawing, then you hire an architect to adapt it to Colorado code and a builder to put it up.
A design-build with the plan included. With Olerra, the plan is the build. The 245, 490, and 735 are already engineered for 165 mph wind and 105 lbs of snow, code-stamped, and state-certified, with the Nichiha and Ceraclad fiber-cement systems giving more than 10,000 exterior combinations. You are not buying a PDF, you are choosing a finished unit. See all three on the Flex Flat models page and real builds in the gallery.

How to Get Started

The fastest way from plan-browsing to a real number is a free property check: tell Olerra your lot and what you want the ADU to do, and you get back a recommended plan, a site layout, and a fixed-price quote. From there, the whole build runs about 5 to 6 months under one contract.

No PDF you cannot build. No hunting for a separate architect and builder. No surprise that your favorite plan does not fit your lot.

→ Get your free property check and quote.

ADU Floor Plan FAQ

Are there free ADU plans in Colorado? Some cities offer pre-approved ADU plans to streamline permitting, and Denver’s West Denver program publishes pre-designed plans. They are free to start from, but you still need site-specific engineering and a builder to construct one.

Do Olerra’s plans come with the build? Yes. Olerra’s 245, 490, and 735 are engineered, code-stamped plans that come as finished modular units, not standalone drawings. The plan and the build are one purchase.

What is the most popular ADU floor plan? The one-bedroom (around 490 to 600 sq ft) is the most-built layout, because it lives like a real home and hits the best rent-to-cost ratio.

What is the smallest ADU you can build? A code-compliant unit lands around 150 to 220 sq ft at the absolute floor, but a livable plan is more like 245 to 300 sq ft. See our Colorado ADU sizes guide for the legal minimums.

Can you customize an Olerra floor plan? The interior layouts are fixed per model, but the design phase shapes finishes, and the exterior offers more than 10,000 combinations. You see interior and exterior renders before you commit.

Do you need an architect for an ADU? For a custom or downloaded plan, usually yes, to adapt it to your lot and Colorado code. With a design-build like Olerra, the engineering and code work are already done.

Ready to Find Your Plan?

The right ADU plan is the one that fits your use, your lot, and the way it gets built in Colorado. A property check lines all three up and shows you the plan and the price in one pass.