Additions and ADUs in Longmont, CO

Space for the People Your Home Has Been Waiting to Welcome

Why Longmont Homeowners Choose Christie's

Because the Home You've Outgrown
Has More Room in It Than You Think

For more than 25 years, Christie’s has helped Longmont homeowners turn the equity sitting in their current home into something their family can actually live in, a garage that’s been storing dusty gear for a decade, finally converted into a two-level ADU with a real kitchen and a mountain view from the balcony. A second-story addition on a ranch that doubles your square footage without touching the backyard. A private in-law suite where your parent has their own entrance and their own space, just close enough.

At Christie’s Design/Build Remodeling, we start by asking what your Saturday morning looks like right now, and what you wish it looked like. We know Longmont’s updated ADU regulations, we know what a pre-1990 panel usually needs before a garage conversion can move forward, and we know how to tell you the honest all-in number before you’ve committed to anything. From Kensington ranches to Old Town bungalows and established neighborhoods near McIntosh Lake, we plan around the home you already have.

In Business

25+ Years

Helping Longmont homeowners convert underused garages, ranch footprints, and untapped square footage into real, independent living space for the people who matter most.

Our Model

One Team

Your Longmont addition or ADU is guided by one coordinated team from garage assessment and design through permitting, construction, and final walkthrough.

Where We Work

Longmont, CO

Serving homeowners throughout Kensington, Old Town, Somerset Meadows, McIntosh Lake, and established neighborhoods across Longmont.

Peace Of Mind

5-Year Warranty

Your new Longmont addition or ADU stays covered after construction ends, so you can settle into the space without worry.

What Makes Additions & ADUs Different In Longmont

The Space You Add
Should Feel Like It Was Always Home

Adding onto a Longmont home means you’re starting with a specific set of conditions, a ranch footprint that hasn’t grown since 1978, a detached garage that’s been storing bikes instead of housing your parent, and lot setbacks that may quietly redirect your first-choice detached ADU toward an attached suite or basement configuration. The families we work with here have usually been thinking about this for a while, and the question that comes up every time is what the project actually costs when you include permits, utility runs, and the panel upgrade that most pre-1990 homes in Kensington and Loomiller need. At Christie’s Design Build, we put all of that on the table before design begins, six-week plan check, utility connection feasibility, lot coverage math, so the number you see is the real one. The goal is an addition or ADU in Longmont, CO that earns its square footage and fits the home so naturally that it’s hard to tell what was always there and what you built.

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Longmont Ranches Have Real Bones

Longmont’s ranch homes, split-levels, and detached garages each create different starting points for added living space. We study your structure and lot first so the right direction is clear before a single line gets drawn.

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Your Ranch Lot Sets the Starting Point

Longmont’s 1960s–1990s ranches carry their own load paths, rooflines, and detached garage configurations. We read those conditions first so the addition connects naturally and holds up as one home.

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Pre-1990 Panels Need a Real Look

In Longmont’s pre-1990 ranches, a single circuit to the garage and an undersized panel are the norm. Finding that early means the budget reflects the real project from day one.

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Longmont's Climate Drives Every Material Choice

Longmont’s freeze-thaw cycles, summer hail, and dry winters put real pressure on roofing, cladding, and insulation, especially where new construction meets old framing. We plan those details so your new space stays comfortable and holds up through every Front Range season.

Longmont, CO Neighborhoods

More Room Without Leaving
the Longmont You Already Call Home

Longmont is full of homes that families bought before the price run-up, 1970s and 1980s ranches in Kensington or off the older residential grid, with detached garages that have solid bones and zero plumbing, sitting twenty feet from the back fence doing nothing useful. Some households need a fully independent space for a parent who wants their own front door, their own kitchen, and the dignity of coming and going on their schedule. Others have an adult child back in the picture, or a caregiver who needs somewhere permanent that isn’t a guest room. Longmont’s updated ADU regulations make the path through permitting more navigable than it was even two years ago, but your specific lot, its setbacks, coverage limits, and utility connections still shape what’s actually possible before design begins. We start every conversation by asking what your family genuinely needs from this space, then work backward from that answer to find the right fit for the home you already own.

Somerset Meadows

When a Well-Built Home Still Has More to Offer

Somerset Meadows was designed from the ground up with quality in mind, larger lots, contemporary finishes, energy-efficient systems already dialed in. But even a newer custom home can leave a family reaching for something it wasn’t originally configured to provide: a fully independent in-law suite for a parent who needs proximity without losing privacy, or a dedicated ADU that earns its keep for years to come. We work closely with Somerset Meadows’ architectural review process from the start, so the addition integrates with the home’s existing design language rather than reading as an afterthought. The lot is already doing most of the work, we help it do the rest.

McIntosh Lake

Add the Space You're Missing Without Losing the View That Sold You

Homes around McIntosh Lake already have the thing most families spend years searching for, water out the window, Long’s Peak on the horizon, and a neighborhood that earns its price tag every single morning. What’s often still missing is the space that lets the whole family actually stay: a private suite where your parent has their own entrance and kitchen, or a garage conversion that finally becomes the independent dwelling someone in your family genuinely needs. We plan every addition around the lake orientation, the sight lines, and the outdoor living this neighborhood is built on, so nothing you add ever crowds out what made you choose this address in the first place.

Clover Creek

When the Family Outgrows the Floor Plan You Loved

Clover Creek’s two-story homes have a lot going for them, good bones, well-kept yards, walkable paths, but a 3-bedroom layout with school-age kids and a parent who needs to be closer has a way of running out of room faster than you’d think. An addition can carve out the dedicated in-law suite, home office, or expanded family area your household actually needs, while a garage conversion can turn underused square footage into a fully independent living space with its own entrance and kitchen. Because Clover Creek’s HOA has an active architectural review process, we handle that approval step before permits are ever submitted, so you’re not spending money on plans that haven’t cleared the right hurdles. Every roofline, exterior material, and proportion gets considered early, so the finished space feels like the home always had it.

Terry Lake

Build Space for the People Sharing Your Life

Terry Lake’s ranch homes from the 1960s and 1970s were built for a specific moment in time, and if your household has shifted, a parent moving closer, an adult child coming back, a family that’s simply grown past three bedrooms, that moment is long past. The detached garages on many of these lots have solid bones and real potential, and an ADU or in-law suite addition can turn that unused structure into independent living space without giving up the lake access and neighborhood character that made staying here the right call. We plan around the original foundation conditions, mountain view lines, and the neighborhood’s mix of vintage ranch and newer custom construction so what gets built looks intentional, not added-on.

Prospect New Town

Build the Space This Neighborhood Was Designed to Grow Into

Prospect New Town draws people who’ve thought carefully about how they want to live, the walkability, the mixed energy, the rooftop terraces, and most of them aren’t going anywhere. But even a well-considered townhome or live/work unit stops fitting when a parent needs independence nearby, or a growing household needs a room that isn’t pulling double duty. The intentional architectural character here means additions and ADU conversions carry real design responsibility. We work with the rooflines, exterior materials, and proportions this neighborhood was built around so whatever we add feels like it always belonged, not like it arrived later and apologized for it.

Our Longmont Additions & ADU Process

From the First Conversation to the Day They Move In

Adding an addition or ADU in Longmont brings questions that are specific to this city, a detached garage with solid bones but no plumbing, a ranch footprint that’s been carrying your family for thirty years, a lot where setbacks may quietly rule out your first idea before design ever begins. A home near Old Town has a completely different set of considerations than a newer build in Somerset Meadows. Our process walks each project through site evaluation, design, permitting, utility coordination, construction, and final completion, one clear track so you always know where things stand.

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Site & Structure Review

Every Longmont addition or ADU starts with a clear-eyed look at what your property can actually do. We walk the lot, assess the existing structure, check setbacks, lot coverage limits, and how your household moves through the home right now. On the ranch homes and detached garages that define so much of Longmont’s established neighborhoods, we also look at foundation conditions, rooflines, and electrical capacity before design decisions get made. That honest groundwork shapes everything that follows.

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Goals & Design Direction

Before plans take shape, we talk through what this space actually needs to do, and who it’s really for. In Longmont, that often means a fully independent ADU where your parent has their own entrance, their own kitchen, and real privacy, or a second-story addition that doubles the ranch footprint your growing family has already outgrown. We think through how the new space connects to your existing home so every decision feels like it belongs there.

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Detailed Project Planning

Once the direction is clear, we translate your goals into a buildable plan grounded in what your Longmont property can actually support. That means working through the six-week plan check window, panel upgrade likelihood if your home was built before 1990, utility-run requirements for a garage conversion, and how new square footage ties into your existing structure. Resolving those specifics before permit submittal is what keeps your project honest and your timeline intact.

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Permits & Trade Coordination

Before construction begins, we coordinate Longmont’s permit filings, plan check submissions, trade scheduling, and any utility-connection sequencing your project requires. We account for the six-week plan check window, material lead times, and the order each specialty trade needs to arrive, especially on garage conversions where water, sewer, and electrical work have to land in the right sequence. That organization gives you one clear point of contact instead of chasing answers from multiple directions.

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Construction & Communication

With Longmont’s permits in place, your new space starts taking real shape. Framing, insulation, mechanical work, drywall, flooring, cabinetry, and finishes all move forward under one coordinated team, whether we’re converting a detached garage into a two-level ADU with a private balcony, adding a second story to a single-story ranch, or building out an in-law suite with its own entrance. You stay informed throughout while we protect the quality and the connection between new and existing.

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Final Review & Completion

When construction wraps, we walk the finished addition or ADU with you and go through every detail together, finishes, fixtures, how the new space flows into the home that was already there. We close out remaining items, confirm everything is working as it should, and make sure the transition between old and new feels natural, not obvious. The goal is a space your parent, your adult child, or your family can move into and immediately feel settled in.

Our Longmont Additions & ADU Process

From the First Conversation to the Day They Move In

Adding an addition or ADU in Longmont brings questions that are specific to this city, a detached garage with solid bones but no plumbing, a ranch footprint that’s been carrying your family for thirty years, a lot where setbacks may quietly rule out your first idea before design ever begins. A home near Old Town has a completely different set of considerations than a newer build in Somerset Meadows. Our process walks each project through site evaluation, design, permitting, utility coordination, construction, and final completion, one clear track so you always know where things stand.

.01

Site & Structure Review

Every Longmont addition or ADU starts with a clear-eyed look at what your property can actually do. We walk the lot, assess the existing structure, check setbacks, lot coverage limits, and how your household moves through the home right now. On the ranch homes and detached garages that define so much of Longmont’s established neighborhoods, we also look at foundation conditions, rooflines, and electrical capacity before design decisions get made. That honest groundwork shapes everything that follows.

.02

Goals & Design Direction

Before plans take shape, we talk through what this space actually needs to do, and who it’s really for. In Longmont, that often means a fully independent ADU where your parent has their own entrance, their own kitchen, and real privacy, or a second-story addition that doubles the ranch footprint your growing family has already outgrown. We think through how the new space connects to your existing home so every decision feels like it belongs there.

.03

Detailed Project Planning

Once the direction is clear, we translate your goals into a buildable plan grounded in what your Longmont property can actually support. That means working through the six-week plan check window, panel upgrade likelihood if your home was built before 1990, utility-run requirements for a garage conversion, and how new square footage ties into your existing structure. Resolving those specifics before permit submittal is what keeps your project honest and your timeline intact.

.04

Permits & Trade Coordination

Before construction begins, we coordinate Longmont’s permit filings, plan check submissions, trade scheduling, and any utility-connection sequencing your project requires. We account for the six-week plan check window, material lead times, and the order each specialty trade needs to arrive, especially on garage conversions where water, sewer, and electrical work have to land in the right sequence. That organization gives you one clear point of contact instead of chasing answers from multiple directions.

.05

Construction & Communication

With Longmont’s permits in place, your new space starts taking real shape. Framing, insulation, mechanical work, drywall, flooring, cabinetry, and finishes all move forward under one coordinated team, whether we’re converting a detached garage into a two-level ADU with a private balcony, adding a second story to a single-story ranch, or building out an in-law suite with its own entrance. You stay informed throughout while we protect the quality and the connection between new and existing.

.06

Final Review & Completion

When construction wraps, we walk the finished addition or ADU with you and go through every detail together, finishes, fixtures, how the new space flows into the home that was already there. We close out remaining items, confirm everything is working as it should, and make sure the transition between old and new feels natural, not obvious. The goal is a space your parent, your adult child, or your family can move into and immediately feel settled in.

What Longmont Homeowners Want From Their Addition or ADU

More Room for the
People Who Matter Most

Addition and ADU projects in Longmont are almost always driven by a moment, a parent who needs to be closer, an adult child who’s back, a detached garage that’s been quietly sitting there for years while your family keeps bumping into each other inside. Longmont’s large inventory of 1960s–1990s ranches with detached garages creates a specific and timely opportunity: those structures already have solid foundations and framing, and post-June 2025 ADU regulations have lowered the barriers to turning them into fully independent dwellings with a private entry, a real kitchen, in-unit laundry, and separate climate control. Kensington and Loomiller ranches in particular tend to have the lot depth and detached garage configurations that make these conversations productive from the first site visit. What Longmont homeowners want most is a space designed for a real family scenario, not a rental unit template, that works beautifully for decades and feels like it was always part of the home.

Space for Every Generation

Space That Earns Its Place

In Longmont's established neighborhoods like Kensington and Loomiller, most ranches were built for households a fraction of today's size, and without the multigenerational configurations families now need. A thoughtful addition or garage conversion can create a genuinely independent suite, open the main living area, or finally give a parent their own front door without leaving the home you already love.

Designs That Shift With Life

Room Already Within Reach

Many Longmont ranches are carrying floor plans that made sense decades ago but feel like a daily frustration now. Rethinking how old and new space connect, with real flow and no awkward transitions, is where these projects start feeling like home again.

Garage Space That Finally Works

Independence Right Out Back

Longmont's larger established lots give you room to solve more than just square footage with the right addition. Built-in storage, a dedicated mudroom, and a properly planned laundry space make the finished area feel calmer and genuinely easier to live in.

Their Own Space, Your Yard

Close, With Their Own Door

For homeowners in Kensington and around McIntosh Lake, a garage conversion or attached in-law suite can make multigenerational living feel genuinely sustainable rather than improvised. A private entrance, a full kitchen, and independent climate control change how the whole arrangement feels, for everyone involved.

Built for Front Range Winters

Designed for Longmont's Real Life

Longmont additions have to hold up against freeze-thaw cycles, hail seasons, and hard winters that test every exterior connection and roofline seam. Exterior cladding, insulated envelope details, and interior finishes chosen for real Front Range conditions keep the new space performing and looking exactly the way it should.

What To Consider When Building An Addition or ADU In Longmont

Plan for the Space Your Longmont Home
Was Always Meant to Hold

An addition or ADU can completely change how a Longmont home holds the people who need to be close, but the best projects start with understanding what the property can honestly support before a floor plan gets drawn. A 1970s ranch in Kensington with a detached garage brings a very different set of possibilities, and real questions about utility runs, panel capacity, and setbacks, than a newer home in Somerset Meadows where a second-story addition makes more sense. Knowing who the space is truly for, what their day needs to feel like inside it, and how all of it connects to your existing home is where the right project actually begins.

Who is this space really for, and what does their day actually look like inside it?

It’s easy to plan around square footage and miss the person. Think about whether your mom will be cooking her own meals in there, whether your adult child needs a quiet place to work from home, or whether a caregiver needs to come and go without moving through your living room. The clearer you are about whose rhythms the space has to hold, the more the design decisions, private entry, kitchen size, soundproofing, start making themselves.
A lot of Longmont homeowners are eyeing that detached garage and seeing a future ADU, and in many cases, the bones are genuinely there. But before you fall in love with a floor plan, it’s worth thinking through what isn’t there yet: water, sewer, and real electrical service rarely exist at the structure, and running those utilities can shift the budget significantly. Getting honest about the starting condition early saves you from a very unpleasant surprise once plans are drawn.
Longmont’s updated ADU regulations have made the permitting path more accessible than it was a couple of years ago, but setbacks, lot coverage limits, and HOA overlay rules can still redirect you from the detached structure you imagined toward an attached addition or basement suite. Finding out early, before you’ve invested in plans, is the difference between a smooth pivot and a frustrating and expensive restart. Your lot’s zoning and your HOA documents are both worth reviewing before design begins.
The construction phase is temporary. The space you’re building is for the long run, and the best projects are the ones where the family eventually stops noticing it’s finished and just lives in it. Think about whether the finishes will still feel right when they’re a few years old, whether the layout will adapt if your parent’s mobility changes, and whether the connection to the main house feels natural or forced. Those are the questions that separate a project you’re proud of from one you’re already mentally revising.

Our Reviews

Trusted by Longmont Homeowners
With the Spaces Their Families Live In

Choosing a team for an addition or ADU in Longmont means trusting them with the space where your family’s evenings will actually unfold, where the light softens, dinner stretches long, and the people you built this for feel genuinely at home. Our reviews reflect the transparency, care, and steady communication Christie’s brings to every Longmont project from the very first conversation through the final walkthrough.

Areas We Service Across Longmont

Space to Stay
Right Here in Longmont

Across Longmont, homeowners are sitting on ranches and split-levels they bought years before prices ran away from them, and they’re realizing the smartest move isn’t to leave, it’s to build what the house has always had the bones for. From the mid-century lots in Kensington and Loomiller with their underused detached garages, to the newer subdivisions in Somerset Meadows where finished secondary suites simply never got built, every property holds a different opportunity. Christie’s works through the real details, setbacks, HOA overlays, utility runs, Longmont’s updated ADU code, and builds space that fits the family you have right now.

Other Areas We Service

Broomfield County

Longmont Addition & ADU Frequently Asked Questions

The Questions Behind
Getting the Space Your Family Actually Needs

Adding onto a home you already love in Longmont brings a particular set of questions, especially when you’re eyeing that detached garage out back and wondering what it would actually cost to turn it into a real dwelling. The answers here depend on your lot’s setbacks and coverage limits, whether your pre-1990 electrical panel can carry the load, how far utility lines need to run to reach a new structure, and what Longmont’s updated June 2025 ADU regulations now allow. Some neighborhoods also layer HOA rules on top of city zoning, and that sequence matters. These are the questions we hear most from Longmont homeowners who want more room without leaving the place they’ve already built their lives around.

Still Have Questions?
We're Here To Help.

How do Longmont's updated ADU regulations affect what I can build on my lot?

Longmont adopted updated ADU regulations in June 2025, bringing the city into alignment with Colorado state law HB24-11. In practical terms, that means some of the barriers that stopped homeowners two or three years ago have been reduced. Detached ADUs, garage conversions, and attached in-law suites are all more accessible under the current framework than they used to be. That said, your specific lot still determines what’s actually possible, setbacks, lot coverage limits, and any HOA overlay rules in your neighborhood all apply on top of city zoning. The best first step is confirming your lot’s eligibility through Longmont’s Zoning Map before you invest in design, and we walk through that with you before anything else.
In most cases, yes, and Longmont’s inventory of detached garages with solid foundations and framing makes this one of the most project-ready starting conditions in the city. What ‘fully independent’ actually requires is water and sewer service run to the structure, a dedicated electrical circuit (most garage panels are a single circuit and will need an upgrade), and HVAC, typically a mini-split system that keeps the ADU climate-controlled without tying into the main home. The good news is that the bones are usually there. The honest news is that utility runs to a detached structure are a consistent budget line item that surprises homeowners who’ve only seen the construction estimate. We put all of that on the table early so there are no mid-project discoveries.
Longmont’s plan check for home additions runs approximately six weeks, and that window sits between the time you submit your permit application and the time you can break ground. It’s a real part of your project timeline, not a footnote. For ADU projects, planning questions go through the city’s Planning and Development Services team, and building permits are handled through the Building Inspection Division at 385 Kimbark St. The design-build approach matters here specifically because when your architect and builder are the same team, the drawings submitted for permit review are already coordinated, fewer revision cycles, fewer delays. We build the six-week plan check window into your schedule from the start so it doesn’t catch your family off guard.
The city doesn’t require HOA approval before permit submittal, but we strongly recommend getting HOA sign-off first, and here’s why. If your HOA restricts or prohibits ADUs in your community, finding that out after you’ve already paid for design work is a genuinely painful experience that we’ve seen happen to homeowners on local forums. In Longmont, older core neighborhoods generally have no HOA, but newer subdivisions on the eastern and northern edges of the city are more likely to have active architectural standards. We help you check both tracks, municipal zoning and HOA rules, before you’ve spent a dollar on plans, so the path forward is clear before you commit.
A garage conversion starts with a structure that already has a foundation and framing, which means you’re not paying to pour a slab or frame walls from scratch. That existing structure meaningfully reduces the starting cost compared to a ground-up build. The trade-off is that the garage’s existing footprint and framing determine your layout options; you’re designing within a box rather than drawing one from scratch. A new detached ADU, on the other hand, lets you purpose-build the layout, aging-in-place accessibility features, specific bedroom orientation for mountain views, an exterior that complements but distinguishes itself from the main home. The right answer depends on what your lot supports, what your family actually needs the space to do, and what timeline works for your household. We walk through both scenarios with you so you can compare them clearly.
For most ADU and garage-conversion projects, yes, your family can stay in the main home through the majority of construction. The work is happening on a separate structure or a defined addition zone, which limits the daily disruption compared to a whole-home remodel. Second-story additions on ranch homes are the most complex from a stay-in-place perspective because roof removal and structural work affect the whole house, but when the project is properly sequenced, temporary weather protection in place, construction phased to minimize open-structure time, most families manage it. We’re honest with you about what each phase actually looks like so you can plan around it, whether that means staying put, staying with family for a few weeks, or making other arrangements for a specific window.
Almost always. Adding a second story to a single-story ranch means the existing wall system has to carry a load it was never designed for. That requires a structural engineer to assess the current framing, specify any reinforcement needed, and sign off on the design before permit submission. The roof comes off and gets rebuilt, which is also the moment to address any existing roofline or envelope issues, especially given Longmont’s hail and freeze-thaw conditions. Mechanical systems typically need to be rerouted to serve both levels. None of this is a reason not to pursue it, second-story additions on Longmont ranches are one of the most efficient ways to double your livable square footage without touching your lot coverage. But it’s scope that rewards an experienced team, not a piecemeal approach.
Yes, and this comes up more often than most homeowners expect. Setback rules and lot coverage limits in Longmont can eliminate the detached ADU option on smaller lots, which redirects the conversation toward attached additions or basement configurations. An attached in-law suite, typically adding four to eight hundred square feet with a private entry, full kitchen or kitchenette, full bathroom with accessibility features, and soundproofed walls, accomplishes the same multi-generational living goal without requiring a separate structure on the lot. Finishing or expanding a basement is another path, particularly for homes in established neighborhoods where the existing footprint already covers most of the lot. We find out early, before design fees accumulate, what your lot can actually support, so the direction you choose is grounded in what’s real.

Start The Conversation

Build the Space
Your Longmont Family Has Needed

When your Longmont ranch has good bones, a detached garage with real potential, and a parent or adult child who needs somewhere to actually land, that’s the moment an addition or ADU stops being a someday idea. A private entrance. A full kitchen. Room to be close without being crowded. Christie’s Design/Build Remodeling walks you through every layer, setbacks, panel upgrades, utility runs, the six-week plan-check window, so nothing surprises you mid-project and what gets built genuinely feels like it belongs.

Our Other Remodeling Services

Kitchen
Remodeling

Basement
Finishing

Whole-Home
Remodeling

Bathroom
Renovation

Deck
Construction

Outdoor
Living Spaces

From The Blog

That Longmont Garage
Could Be Home for Someone You Love

When you’re turning a detached garage into a real home for someone in your family, or adding a full second story to a Longmont ranch, the questions stack up fast, from permit timelines to utility runs to what finishes actually hold up here. Our blog tackles those decisions honestly, so you walk in informed, not surprised.