Contact Us
(303) 833-4715
Contact Us
(303) 833-4715

Northern Denver & Front Range's Premier Design-Build Firm

Additions & ADUs in Boulder, CO

Building the Space Your Boulder Life Actually Needs

Start Planning Your Project

Why Boulder Homeowners Choose Christie's

Because the Home You Already Love
Should Have Room for Everyone Who Matters

For more than 25 years, Christie’s has helped Boulder homeowners build the space their lives have been quietly asking for. A detached ADU where aging parents stay close without giving up their independence. A second story that finally gives everyone room to breathe. A bump-out that turns a cramped kitchen into the place your family actually gathers on Saturday mornings.

At Christie’s Design/Build Remodeling, we start where it matters, with why more space matters to you right now. Boulder’s proportional energy code, historic overlay zones in neighborhoods like Mapleton Hill, and expansive soil conditions are the kind of details we plan around from day one, not surprises we hand you after permit submission. From ranch homes in South Boulder to Craftsman bungalows near the Hill and established properties across the city, we design and build additions and ADUs around the home you already own, and the life you’re building there.

In Business

25+ Years

Helping Boulder homeowners make more room for aging parents, adult children, rental income, and the next chapter of life at home.

Our Model

One Team

Your Boulder addition or ADU stays with one coordinated team from early design through construction, finishing, and the final walkthrough.

Where We Work

Boulder, CO

Serving homeowners throughout Mapleton Hill, South Boulder, University Hill, Pine Brook Hills, and established neighborhoods across Boulder.

Peace Of Mind

5-Year Warranty

Your new addition or ADU in Boulder stays protected after construction, so you can settle into the space with real confidence.

What Makes Additions & ADUs Different In Boulder

More Space Has to Feel
Like It Was Always Part of the Plan

Adding onto a Boulder home means holding two things at once: the house you already love and the life you’re trying to make room for. Victorian bungalows in Mapleton Hill, mid-century ranches in South Boulder, and split-levels across the older grid each carry their own structural story, load paths, rooflines, expansive soil conditions, and in historic overlay zones, a design-review step that can catch you off guard if nobody flagged it early. At Christie’s Design/Build, we look at the whole picture before scope is ever set. The goal is an addition or ADU that fits the home so naturally your family stops noticing where the old part ends and the new part begins.

.01

Boulder Homes Span Every Era

Boulder’s Craftsman bungalows, postwar ranches, and split-levels each open up differently when it comes to adding space. We study the existing structure and lot conditions first so the addition starts from the right place.

.02

Your Existing Home Sets the Rules

Boulder’s older homes carry their own structural logic, load paths, rooflines, and foundation conditions that vary block by block. Reading those conditions early means the addition connects naturally rather than feeling grafted on.

.03

Older Boulder Homes Hide Surprises

Opening walls in older Boulder homes often surfaces wiring, plumbing, or HVAC that’s overdue for an update. Catching those needs in planning keeps the budget honest and construction on track.

.04

Boulder's Climate Shapes Every Detail

Boulder’s intense sun, hard winters, freeze-thaw cycles, and dry air put real demands on exterior materials, roofing, and insulation choices. We plan those details upfront so the new space stays comfortable through every season, year after year.
See Our Work

Boulder, CO Neighborhoods

More Room Without Leaving
the Boulder You Love

Boulder is filled with homes people have genuinely grown into, ranch layouts from the 1960s, split-levels near South Boulder trails, Craftsman bungalows on Mapleton Hill, and that history is exactly why an addition or ADU can carry so much weight. Some families need a private space for a parent who wants to stay close but keep their independence. Others are finally converting a cold, underused garage into something the whole household actually benefits from. Sometimes a second story is the only move that makes staying put feel better than the risk and cost of selling into a $1.3M median market. Across Boulder’s neighborhoods, what’s possible depends heavily on the lot, the era of the home, and whether you’re in a historic overlay zone that shapes what any addition can look like from the street. We work through all of that with you early, before decisions get made that are hard to undo, so the space you end up with genuinely fits how your family lives now, and where you’re heading.

Newlands

Let an Old Newlands Home Finally Fit Your Life

Newlands has the kind of in-town character that makes people plant roots and stay. When a 1920s or ’40s cottage starts to feel too small for the family living in it, an addition, or a detached ADU tucked into that larger lot, can change everything without uprooting anyone. That might mean a primary suite above the original footprint, a garage conversion for an aging parent, or a full detached ADU that generates income while the family stays put. We assess each home individually, because a cottage from 1932 and a modern infill build two doors down are completely different structural conversations.

North Boulder

Grow the Space Without Changing What the Neighborhood Loves About It

Homes in North Boulder, the Craftsman bungalows, mid-century ranches, and Tudor cottages that give this neighborhood its feel, were built with character baked in, and the families living in them now want more room without losing what drew them here in the first place. A second-story addition, an in-law suite, or a detached ADU tucked into the backyard can give you that space, a private setup for aging parents, a rentable unit that finally puts that underused garage to work, or a primary suite that actually fits how your household lives today. We work within each home’s existing architecture and historic overlay requirements so the new square footage reads like it always belonged there, not like something bolted on after the fact.

Table Mesa

Give Your Ranch Home the Room Your Family's Already Outgrown

The ranch-style and split-level homes that line Table Mesa’s streets were built for a different era of family life, and if yours has started to feel a little tight, that’s not a sign to move, it’s a sign to build. A second-story addition, a garage conversion ADU, or a carefully designed in-law suite can give your family the breathing room it needs without leaving a neighborhood you’ve worked hard to stay in. Midcentury homes carry their own structural personality, and we know how to work with original framing, rooflines, and proportions rather than against them. The result feels like it was always there.

Chautauqua

Honor What's Here. Build What's Next.

The brick Tudor or bungalow you chose in Chautauqua was never just a house, it was a commitment to a particular kind of life, close to the foothills, rooted in real architectural character. But the family inside it keeps evolving, and sooner or later the rooms stop matching how you actually live. An addition or ADU here means working within the historic design language, matching original materials, respecting rooflines, navigating any HOA review, so the new space feels like it always belonged rather than something grafted on. We carry that process from the first design conversation through the final inspection, keeping the home’s integrity intact while finally giving your household the room it needs.

Mapleton Hill

Honor the Home That's Already a Legacy

People who chose Mapleton Hill weren’t looking for a blank slate, they fell in love with a Victorian that already had a century of life in it, and they intend to stay. When a parent needs to move closer, or a family simply outgrows rooms that weren’t built for modern living, an addition or ADU becomes the answer that doesn’t ask you to give up what you love. That work here is genuinely different from anything we do in newer neighborhoods, the historic overlay means every design decision is reviewed for compatibility with period architecture, original massing, and the tree canopy that defines these streets. We carry that sensitivity into every detail, from roofline pitch to window proportions, so the space you add feels like it belongs to the home rather than sitting awkwardly beside it.

Our Boulder Additions & ADU Process

From First Conversation to Finished Space

Finishing a basement in Arvada comes with decisions that are genuinely specific to your home, your neighborhood, and the way you plan to use the space, a mid-century ranch near Alta Vista may call for a very different layout than a newer home in Leyden Rock with taller ceilings and more room to work with. Our process guides each project through evaluation, design, permitting, construction, and final completion, keeping every phase clear and making sure the finished basement feels comfortable, intentional, and fully connected to the rest of your home.

Start Planning Your Project
(303) 833-4715

.01

Site & Structure Review

Your Boulder property tells us a lot before design even starts. We look at your lot, setbacks, existing structure, and how your household actually moves through the home today. Boulder’s expansive soils, roofline conditions, and load-bearing realities all factor into how new square footage can connect safely. Starting here means design decisions are grounded in what your specific property can actually support.

.02

Goals & Design Direction

Before plans take shape, we talk through what this new space actually needs to change for your family, whether that’s a private entrance for aging parents, a second story that finally gives everyone room to breathe, or a detached ADU your adult child can actually afford to live in near Boulder. We think through how circulation, storage, and access connect the new space to your existing home so it never feels like an afterthought.

.03

Detailed Project Planning

Once the direction is clear, we translate it into a buildable plan that accounts for Boulder’s proportional energy code triggers, historic overlay conditions if they apply to your neighborhood, and the structural details your property requires. Foundation work, utility coordination, interior layouts, and material selections all get resolved here. You’ll understand exactly how the addition or ADU comes together before a single permit is filed.

.04

Permits & Trade Coordination

Before construction begins, we handle the permits, approvals, and trade scheduling that Boulder projects require, including design review submissions for historic overlay zones when your home calls for it. We manage review timelines, material lead times, and the sequencing each specialty trade needs. That coordination means you’re not chasing inspectors or suppliers yourself, you have one clear point of contact the whole way through.

.05

Construction & Communication

With approvals in place, your new space starts coming to life. Framing, insulation, mechanical systems, drywall, flooring, and finishes all move forward under one coordinated team, whether we’re building a detached ADU, a pop-top addition, or a multigenerational in-law suite. We keep you informed at every stage and protect the quality and continuity between the new space and the Boulder home you already love.

.06

Final Review & Completion

As construction wraps up, we walk the finished addition or ADU with you and go through every detail together. We confirm finishes, work through any remaining items, and make sure the new space connects naturally to the rest of the home, whether that’s a step-free threshold for a parent moving in or the right amount of soundproofing between units. The goal is a space that feels completely settled the day you start using it.

Our Boulder Additions & ADU Process

From First Conversation to Finished Space

Adding an addition or ADU in Boulder comes with questions that are genuinely specific to your property, your neighborhood, and the home already standing, a Craftsman bungalow in Mapleton Hill carries different design-review expectations than a ranch-style home in South Boulder with room to grow out back. Our process walks every project through site evaluation, design, permitting, construction, and final completion, keeping each phase clear and making sure the space that results feels like it’s always been part of your home.

.01

Site & Structure Review

Your Boulder property tells us a lot before design even starts. We look at your lot, setbacks, existing structure, and how your household actually moves through the home today. Boulder’s expansive soils, roofline conditions, and load-bearing realities all factor into how new square footage can connect safely. Starting here means design decisions are grounded in what your specific property can actually support.

.02

Goals & Design Direction

Before plans take shape, we talk through what this new space actually needs to change for your family, whether that’s a private entrance for aging parents, a second story that finally gives everyone room to breathe, or a detached ADU your adult child can actually afford to live in near Boulder. We think through how circulation, storage, and access connect the new space to your existing home so it never feels like an afterthought.

.03

Detailed Project Planning

Once the direction is clear, we translate it into a buildable plan that accounts for Boulder’s proportional energy code triggers, historic overlay conditions if they apply to your neighborhood, and the structural details your property requires. Foundation work, utility coordination, interior layouts, and material selections all get resolved here. You’ll understand exactly how the addition or ADU comes together before a single permit is filed.

.04

Permits & Trade Coordination

Before construction begins, we handle the permits, approvals, and trade scheduling that Boulder projects require, including design review submissions for historic overlay zones when your home calls for it. We manage review timelines, material lead times, and the sequencing each specialty trade needs. That coordination means you’re not chasing inspectors or suppliers yourself, you have one clear point of contact the whole way through.

.05

Construction & Communication

With approvals in place, your new space starts coming to life. Framing, insulation, mechanical systems, drywall, flooring, and finishes all move forward under one coordinated team, whether we’re building a detached ADU, a pop-top addition, or a multigenerational in-law suite. We keep you informed at every stage and protect the quality and continuity between the new space and the Boulder home you already love.

.06

Final Review & Completion

As construction wraps up, we walk the finished addition or ADU with you and go through every detail together. We confirm finishes, work through any remaining items, and make sure the new space connects naturally to the rest of the home, whether that’s a step-free threshold for a parent moving in or the right amount of soundproofing between units. The goal is a space that feels completely settled the day you start using it.
Start Planning Your Project
(303) 833-4715

What Boulder Homeowners Want From Their Addition or ADU

More Room for the
Life You're Staying For

Addition and ADU projects in Boulder are rarely about square footage for its own sake. Most homeowners are trying to solve something that comes up every week: a parent who needs to be closer but not under the same roof, an adult child who can’t afford Boulder’s housing market on their own, or a home that was perfectly sized in 2005 and simply isn’t anymore. Older homes near Mapleton Hill and University Hill bring their own layer of complexity, historic overlay zones, design review, the occasional unpermitted garage conversion that needs to be sorted before anything else moves forward, while mid-century ranches across South Boulder often have the lot room for a detached ADU but need careful energy code planning before scope gets set. What Boulder homeowners want most is a space that feels completely natural to the home they already love, handled by a team that knows this city’s process well enough to keep things from stalling.

Space for Every Generation

Space That Finally Fits

In established Boulder neighborhoods like Mapleton Hill and the Newlands area, many homes were built for a much smaller household than the one living there now. A well-planned addition can open up the main living area, add a primary suite, or create a fully independent space for family without anyone having to leave the neighborhood they love.

Layouts That Adapt With You

Room to Grow Into

A lot of Boulder's mid-century ranches and split-levels were designed for a smaller household and a different era. Connecting old and new space thoughtfully means better flow, fewer pinch points, and a home that actually fits the way your family lives now.

Built-In Storage That Actually Works

A Place for Everyone

Boulder lots often have more potential than homeowners realize, enough room for a detached ADU, a bump-out, or built-in storage that finally makes the main house feel calm. The right scope turns underused backyard or garage space into something that works every single day.

Independence Without Moving Away

Close, With Room Apart

For homeowners in South Boulder and near the Chautauqua neighborhoods, a detached ADU or private in-law suite can make multigenerational living feel like a gift instead of a compromise. Separate entrances, independent climate control, and thoughtful soundproofing give everyone real privacy while keeping family genuinely close.

Finishes Built for Boulder Life

Made for Boulder Living

Boulder additions need to handle freeze-thaw cycles, strong high-altitude sun, trail mud, and the kind of winters that test every exterior material you choose. Durable cladding, high-efficiency windows, and practical interior finishes help the new space hold up beautifully to the way Colorado families actually live.

What To Consider When Building An Addition or ADU in Boulder

Build the Space Boulder's
Next Chapter Deserves

Your Boulder home has likely been carrying your family through a lot of life already, and an addition or ADU can reshape how it carries you through what’s next, but the projects that land right start with more than a square-footage number. A Craftsman bungalow on Mapleton Hill sits inside design-review guidelines that a ranch in South Boulder doesn’t, while expansive soils, utility placement, and Boulder’s proportional energy code can all quietly reshape scope before a single nail goes in. Knowing what the space needs to solve, and who it’s really for, before design begins is what separates a project you love from one you just finish.

Who is this space really for, and how might that change in five years?

It sounds simple, but the honest answer shapes everything, the entrance location, the kitchen size, the bathroom accessibility, even the soundproofing spec. An ADU built for aging parents who need step-free access and a walk-in shower is a different project than one built to generate rental income from a CU grad student. And both are different from a second-story addition designed so your adult kids have a real reason to come home. Think through not just who needs the space today, but who might need it differently by the time Boulder’s next decade plays out.

In most markets this is a close call. In Boulder, it often isn’t. When the median home is sitting near $1.3M and inventory stays tight, the transaction costs alone on buying up, agent fees, closing costs, moving, and the premium you’d pay to get more square footage, can push past what a second-story addition or detached ADU would cost on a lot you already own. Add in Boulder’s 2025 rule change that lets you rent both your primary residence and your ADU simultaneously, and the financial math shifts again. It’s worth running the real numbers before you assume moving is the simpler path.
Boulder has layers that aren’t visible until someone goes looking. If your home is in or near a historic overlay zone, Mapleton Hill, parts of North Boulder, University Hill, design review is a real step, not a formality, and it happens before permits move forward. If a previous owner converted a garage or finished a basement without pulling permits, that history surfaces during discovery and has to be addressed before new construction can proceed. Lot coverage limits, utility tie-in locations, and Boulder’s expansive soil conditions all shape what’s practical. Knowing your starting point honestly is what keeps the scope realistic from day one.
This is the question that gets skipped most often, and it’s the one that matters most when the project is done. The first morning your parent makes coffee in a space that actually feels like theirs. The evening your family stops noticing the addition and just uses it. That shift, from ‘construction project’ to ‘this is just how our home works now’, happens when the design was built around how people actually live, not just around what the permit allows. Before scope gets set, it helps to name the moments you’re building toward, because those moments are what the space is really for.

Our Reviews

Trusted With The Space
Beneath Your Home

Choosing a team to finish your basement in Arvada means trusting them with a space your family may use for years to come. You want to know the people working inside your home will communicate clearly, respect the space, and care about the details. Our reviews reflect the honesty, communication, and care Christie’s brings to every Arvada basement finish, from the first conversation through the final walkthrough.

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Areas We Service Across Boulder

More Space in Boulder,
Right Where Your Life Already Is

Across Boulder, homeowners are finding that the lot they already own is often the smartest investment they can make, especially when the median home price makes buying up feel like trading one tight space for another expensive one. From Craftsman bungalows in Mapleton Hill navigating historic design review to ranch-style homes in South Boulder with room for a detached ADU out back, every property tells its own story. Whether you’re creating a private space for aging parents, a rental that finally makes the math work, or simply the room your family has needed for years, Christie’s walks the whole process with you, design, permits, and construction, right here in Boulder.

  • Ralston Valley
  • Oberon
  • Pomona Lakes
  • Whisper Creek
  • Spring Mesa
  • Olde Town Arvada
  • Allendale
  • Lake Arbor
  • Scenic Heights
  • Alta Vista
  • Club Crest
  • Hackberry Hill
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(303) 833-4715

Other Areas We Service

Weld County

Greeley, CO
Erie, CO
Fort Lupton, CO
Firestone, CO
Frederick, CO

Boulder County

Lafayette, CO
Longmont, CO
Louisville, CO

Adams County

Brighton, CO
Commerce City, CO
Northglenn, CO
Thornton, CO

Jefferson County

Arvada, CO
Westminster, CO

Broomfield County

Broomfield, CO

Larimer County

Loveland, CO
Windsor, CO

Boulder Addition & ADU Frequently Asked Questions

The Questions Worth Asking
Before You Build in Boulder

There’s something particular about deciding to build on a home you’ve already put years into, the questions feel heavier, and more personal. In Boulder, the answers depend on everything from your lot’s soil conditions and historic overlay status to how the addition’s size compares to your existing home under the city’s energy code. Boulder also has specific permitting requirements, design review steps for certain neighborhoods, and ADU rules that have genuinely changed in the last two years. These are the questions we hear most from homeowners who’ve decided they’d rather build on what they love than start over somewhere else.

Still Have Questions?
We're Here To Help.

Contact Us
(303) 833-4715

How long does the full addition or ADU process take in Boulder from first conversation to move-in?

Honestly, it’s longer than most homeowners expect, and knowing that upfront saves a lot of frustration. Design and permitting in Boulder typically run five to eight months on their own, and construction adds another three to eight months depending on the scope and complexity. For a detached ADU or a second-story addition, you’re looking at eight to sixteen months end-to-end. Boulder’s permit review for detached ADUs has genuinely gotten faster since the 2023 streamlining, roughly three weeks for the ADU permit itself, but the full process still includes design development, structural engineering, energy compliance review, and city approval. We map that timeline honestly at the start so you can plan your family’s life around it, not the other way around.
Yes, and that’s a recent change that matters. As of 2025, the City of Boulder removed the owner-occupancy requirement for ADU rentals, which means you can rent both the primary home and the ADU at the same time, even if you’re not living on site. That changes the financial picture considerably. The one firm restriction to know: Boulder ADUs are limited to long-term rentals. Short-term rental platforms like Airbnb are not permitted for ADUs within city limits. If rental income is part of your reasoning for building, we’ll walk through what that looks like realistically, layout, separate entrance, independent utilities, so the space is set up to actually function that way from day one.
This is one of the most consistent mid-planning surprises we see, so we’d rather you hear it early. Boulder’s energy code scales with how large your addition is relative to the existing home, the bigger the addition proportionally, the more extensive the whole-home energy upgrades the city may require. That can mean insulation improvements, HVAC upgrades, or window replacements in parts of the home you weren’t originally planning to touch. It doesn’t make a project undoable; it just needs to be scoped and budgeted before you’re already three months into design. We factor this in from the first conversation so there are no surprises at permit submission.
It does, and it’s worth understanding before you get too far into planning. Mapleton Hill sits within Boulder’s historic overlay zone, which means any exterior alteration, including an addition, goes through a design review step before the building permit can be issued. The city has formal guidelines that define character elements like massing, rooflines, porch configurations, and materials. That doesn’t mean additions aren’t possible; plenty of beautiful ones have been done. It does mean the design has to be developed with those guidelines in mind from the start, not retrofitted to them after a permit rejection. If you’re in a historic overlay area, we build that review step into the process so it’s an expected part of the project, not a detour.
It can, and it’s worth finding out now rather than during permit review. Unpermitted conversions are fairly common in older Boulder homes, and they create legalization exposure: the work may need to be documented, inspected after the fact, or in some cases brought up to current code before new permitted work can proceed. The scope of that varies widely depending on what was done and when. The good news is that discovering it during discovery, not mid-construction, gives you options and keeps the project on track. We look for this specifically during the early planning phase so there are no mid-build surprises.
The short version: detached ADUs offer the most privacy and independence but come with the highest cost and complexity since you’re essentially building a small home from scratch on the same lot. Attached ADUs share at least one wall with the primary residence, which can reduce construction costs but requires careful soundproofing and design to make both units feel genuinely separate. Garage conversions work with an existing structure, which can lower the cost floor, but they almost always need full utility tie-ins, insulation, and sometimes foundation work, so the savings are real but not as dramatic as the lower sticker might suggest. Boulder’s city code caps detached ADUs at one thousand square feet, though an affordable ADU bonus program allows up to twelve hundred square feet for homeowners who commit to below-market rents. Which type makes the most sense depends on your lot, your use case, and your budget, and we’re happy to walk through that with you before anything is decided.
This is the conversation we have most often, and it’s one we genuinely love because the details matter so much. For aging-in-place use, step-free thresholds at every entry are non-negotiable, especially in Boulder where you might have a grade change between the main home and a detached structure. Wider doorways, a walk-in shower sized to accommodate mobility aids, blocking in the walls for future grab bars, and a ductless mini-split system for independent climate control all make a real difference in how livable the space is five and ten years from now. A separate entrance with its own outdoor space, even a small covered porch, gives your parents genuine independence without isolation. These aren’t add-ons; they’re the things we spec from the beginning when we know the use case.
Boulder’s expansive soils are a real site variable, and they affect foundation work in ways that don’t show up in a per-square-foot construction estimate. When soil expands and contracts with moisture, it puts lateral and vertical pressure on foundations, which means a detached ADU or a bump-out addition needs a foundation designed with that in mind, not just the standard approach. A geotechnical assessment is typically part of the planning process for new foundation work in Boulder, and the results shape the foundation design. The good news is that this isn’t a project-stopper, it’s a known condition here, and a firm with local site experience will account for it in the structural design from the start rather than discovering it after the slab is poured.

Start The Conversation

Build the Space Boulder
Your Family Actually Needs

When your Boulder home still feels right but the space no longer does, an addition or ADU can change everything. Room for an aging parent who needs to be close, but not that close. A place for an adult kid priced out of this market. A backyard structure that finally earns its keep. Christie’s Design/Build Remodeling carries the full process, design, permits, construction, so you’re not stitching it together yourself. No hand-offs, no surprises. Just a space built around how your family actually lives in Boulder.

Start Planning Your Project
(303) 833-4715

Our Other Remodeling Services

Kitchen
Remodeling

Learn More

Basement
Finishing

Learn More

Whole-Home
Remodeling

Learn More

Bathroom
Renovation

Learn More

Deck
Construction

Learn More

Outdoor
Living Spaces

Learn More

From The Blog

Your Boulder Home, Built
for the Life Ahead of You

Planning an addition or ADU in Boulder comes with real questions, about historic overlay zones, energy code triggers, permit timelines, and what it all actually costs on your specific lot. Our blog walks through the decisions that matter most, so you feel clear and confident before anything gets built.