Adding On Without the Guesswork
Wondering what a home addition actually costs before you call anyone? Worried the number you find online won’t match a real quote?
In this post, you’ll learn what a home addition costs in our area, what moves that number up or down, and why two quotes for the same project can look so different.
By the end, you’ll know how to read an addition quote, what’s worth paying for, and whether an addition is the right call for your family.
What Does a Home Addition Cost in the Denver Metro Area?
“Home addition” covers a lot of ground, and so does the price.
A home addition in our area typically starts around $250,000 and climbs from there based on its size, the type of addition, and how much it ties into your existing home. They can even get up to the $1 million range.
The Types of Additions We Build and How Each One Moves the Price
The type of addition you choose is a big part of what sets your budget.
Bunn & Sons Custom Builds builds additions that add real, finished living space, from a single new room to a full second story.
We don’t take on small bump-outs, decks, patios, or repair-only work.
A Single New Room
A single new room is one finished space added onto your existing home, like a bedroom or a dedicated home office.
Homeowners usually reach for one when running out of bedrooms or there’s nowhere quiet to get work done.
It’s the simplest type of addition, so it sits at the lower end of the cost range.
Check out this room addition (and more) we did in Flatiron.
A Primary or In-Law Suite
Here’s a video testimonial of a first-floor bedroom addition we built in Longmont.
A suite is a bedroom built together with its own bathroom and closet as one connected space.
Families add one when a parent is moving in, or an adult child is coming home, and the house has no room for them.
Because a suite includes a bathroom, it brings plumbing into the project, which increases the cost.
We build these for families sharing a home across generations, and we plan the suite, its bathroom, and how it connects to the rest of the house together so the new space flows with the old one.
A Second-Story Pop-Top
A pop-top adds a second story on top of your existing home instead of expanding the footprint outward.
It lands at the higher end of the range because of what it takes structurally.
When we build up, that means reinforcing the existing structure, removing and reframing the roof, and reworking your stair access.
A Kitchen-Plus Main-Floor Addition
A kitchen-plus addition isn’t a single room; it’s a main-floor reconfiguration built around the kitchen.
It usually means opening up a closed-off main floor so the kitchen, dining, and living areas work together.
Because the kitchen anchors it, this is the most finish-heavy type of addition.
Your material choices drive the number more here than anywhere else, so this is the type where the selections you make in our design phase show up most directly in the budget.
What Actually Drives the Cost of an Addition
Once you know the type, a handful of factors decide where your project lands.
Some are about the addition itself, and some are about the house it’s attaching to.
Here’s what moves the number the most:
- Size and square footage, since more space means more materials, labor, and systems work.
- How it connects to your home, including foundation work, structural beams, and the engineering that supports a second story.
- Roofline tie-in and exterior matching, so new siding, trim, and windows blend with the original house.
- Mechanical systems, since heating, plumbing, and electrical often need to be extended or upgraded for the new space.
- Finish level, from flooring and tile to cabinetry and fixtures.
- Site and access, since a flat lot with easy access costs less to build on than a tight or sloped one.
Even a foothill lot like the ones around Golden can change the engineering, which we plan for before we price the job.
Every jurisdiction we work in handles permits and energy codes a little differently, which can affect the price as well. We manage all of that as part of the project.
Why a Price Per Square Foot Won’t Tell You Much
You’ll see national calculators quote a tidy figure like $160 to $420 per square foot for Colorado.
The trouble is that the number averages a small bump-out and a full second-story addition with a new kitchen into one figure.
That average barely resembles what a real, complex addition costs once structural, mechanical, and finish work are priced properly.
Local energy codes, design review, and a competitive labor market push real pricing here above what those calculators assume.
A per-square-foot figure isn’t really wrong; it’s just answering a different question than the one you’re actually asking.
Why Two Addition Quotes Can Look So Different
Getting a few quotes and seeing a wide spread is normal, and it rarely means one builder is just charging more.
Most of the gap comes down to what’s actually inside each bid.
We commit to a fixed-price contract, not an open-ended, time-and-materials number.
We get there in two steps: a Project Development Agreement that plans and prices every detail first, then a fixed-price build contract.
The number you sign is the number you pay, outside of changes you choose to make.
Here’s how a complete bid stacks up against a cheaper one:
| What our price includes | What a cheaper bid often leaves out |
|---|---|
| Full design and engineering, settled before pricing | Design figured out on the fly, mid-build |
| Permit management and inspections | Permits you’re left to chase yourself |
| Structural work and the tie-in to your home | The structural connection, priced as a change order later |
| A dedicated superintendent or project manager running your job day to day | The real cost of daily management, skipped when one person is stretched across many jobs |
| Real finish and fixture selections | Placeholder allowances that grow over time |
| A fixed price and a detailed schedule | An open-ended number that climbs through change orders |
That management line is the one that quietly disappears from a lot of bids.
Running a remodel or addition well takes a superintendent or project manager 15 to 30 hours a week, which is half to three-quarters of a full-time person for the length of your build.
That adds up fast over the months a project runs.
Without someone whose job is your project (and who isn’t already stretched across ten others), your build starts to slip.
Beyond the price itself, a few things in a bid are worth a closer look.
They’re the spots where a low number usually hides its gaps:
- A price handed to you without an in-home visit, since a firm number takes seeing the house.
- A vague, one-page scope, which is where change orders hide.
- A jump straight from a ballpark guess to swinging hammers, with no real planning in between.
It helps to know what to look for when hiring.
Is a Home Addition Worth It for Your Family?
An addition is a real investment, so the honest answer depends on your situation.
Many homes around Boulder were built with layouts that don’t match how families live now.
It’s usually the right move when:
- When you love your location and lot, but your house has run out of room.
- If your street, schools, and neighborhood are right.
- When the need is structural, not cosmetic, like a real bedroom suite, a dedicated workspace, or a kitchen and family room that finally works.
It’s probably not the move if you only need cosmetic updates, if you’re planning to sell in the next couple of years, or if your lot and zoning won’t support the space you want.
An addition adds value, but you usually won’t get the full cost back if you sell soon after the work is done.
How Long Does a Home Addition Take?
Timeline tracks scope, just like cost does.
A simple single-room addition usually runs about 3 to 4 months of build time.
Larger additions with a full kitchen, a second story, or major foundation work can run 6 to 9 months or more.
Before we break ground, every project gets a firm schedule built during planning, and you get regular updates plus your own online project log, so you always know where things stand.
Your Next Room Starts With a Real Number From Bunn & Sons
We plan every detail of your addition before we start, then hold to a fixed-price contract for the build.
The result is a new space that adds real room and ties into the home you already own, without the budget moving around on you mid-project.
If you want a real number for your home instead of a rough guess, fill out our contact form today or give us a call.
