Home Additions
Updated September 2026
Building up adds rooms without losing yard, and it changes the whole house: the foundation carries more, a stair takes a room downstairs, the roof comes off. Here's how feasibility is checked and how it compares to building out.
9 min read
Written by Mike Schwartz, Built by Design | Published May 4, 2026
A second story is the addition people reach for when the lot is tight or the yard matters: it adds bedrooms and a bath without touching the footprint. It's also the addition that changes the most of the existing house. The foundation and the walls below have to carry a floor they weren't built for, a stair has to land somewhere on the main level, the roof comes off while the new floor goes on, and the family usually lives somewhere else for part of it.
This guide walks the feasibility questions in the order a design-build team checks them, with the code numbers for the stair, what zoning limits to verify with your city, and an honest comparison with building out. One thing to say plainly: Built by Design's published case studies include a roughly 1,000 square foot ground-floor addition in Overland Park but not a completed second story, so the addition examples here are that project, and the second-story guidance is the process, not a photo tour.
For the money side of the same decision, read is a home addition worth it in Johnson County and what a home addition costs in Kansas City. For the service, see home additions with Built by Design.
A one-story house was designed to carry its roof. A second story asks it to carry a floor, walls, a new roof, and the people and furniture on that floor, and the load has to get from the new floor to the ground through a continuous path: floor joists to bearing walls to the foundation to footings. A structural engineer evaluates each link: the footing size and the soil, the foundation wall or slab, which main-level walls are bearing and whether they line up with the new loads, the headers over the openings in those walls, and the connections between all of it. The answer is rarely "no" and rarely "as is." It's usually a list: a new beam and posts under the new floor where the walls don't line up, new footings under those posts, sistered or added studs in a bearing wall, and in older houses, work on a foundation that has already settled. Get this evaluation before anyone draws bedrooms, because it decides where the new walls can go and how much of the main level gets opened to do the work. Bring any existing drawings and records of prior remodels; the engineer will still need to see the house.
The stair is the decision that most changes the main floor. A code stair is at least 36 inches wide, with risers no taller than 7¾ inches and treads at least 10 inches deep, 6 feet 8 inches of headroom, and a landing at the top and bottom (IRC R311.7). For a typical 9-foot floor-to-floor, that's about 14 risers and a straight run of roughly 11 to 12 feet, plus landings: call it a 3-by-14-foot slot through the main level, or an L or U shape with a landing that takes a squarer footprint. Somewhere downstairs, that footprint is a room, a hallway, or a garage bay. Decide the stair location first, on both floors at once. It wants to land in circulation, not in the living room; it wants daylight if it can get it; and upstairs it wants to arrive at a hall that reaches every bedroom without cutting through one. Your city's inspector confirms the edition of the code it enforces; the numbers above are the residential code Johnson County cities adopt.
| Stair element | Code minimum (IRC R311.7) | What it means for the plan |
|---|---|---|
| Width | 36 inches clear | A 3-foot slot plus walls, about 4 feet of floor width |
| Riser height | 7¾ inches maximum | About 14 risers for a 9-foot floor-to-floor |
| Tread depth | 10 inches minimum | A straight run of roughly 11 to 12 feet |
| Headroom | 6 feet 8 inches | Decides where the stair can pass under the existing ceiling |
| Landings | At top and bottom, at least 36 inches deep | Adds 3 feet at each end, or the corner of an L |
At some point the existing roof comes off and the house is open to the sky until the new floor and roof are on. The plan has to say how that's sequenced and protected: how much roof comes off at once, what temporary roofing or tarping covers the house, how the ceiling below is protected, what happens to the attic's insulation and the ductwork and wiring that live up there, and which season the work is scheduled for. Kansas City weather makes this a real design question, not a detail. A good schedule takes the roof off when the framing crew and the materials are ready to close it fast, and it builds weather days into that stretch. The new roof also has to meet the old one where the second story doesn't cover the whole footprint, and the exterior has to read as one house: siding, windows, trim, and roof pitch chosen to match or deliberately contrast. That's the part neighbors see, and it's the part a rushed second story gets wrong.
A second floor with bedrooms and a bath adds heating and cooling load, electrical load, and plumbing that has to reach the main stack and vent through the new roof. The HVAC question is whether the existing system can serve a new zone or whether the second floor gets its own; a single system pushed to serve two floors is how upstairs bedrooms end up hot in July. The electrical question is panel capacity: an addition often triggers a panel upgrade, which is its own permit and inspection. The plumbing question is where the bathroom sits relative to the existing stack, because the drain has to reach it with slope, and the closer the new bath is to the old one, the shorter that run.
Before design, verify three things with your city's planning or building department: the maximum building height in your zoning district (many residential districts cap it in the low thirties of feet, and a second story on a raised ranch can get close), the setbacks (a second story usually stays inside the existing footprint, but a bump-out or a new stair enclosure may not), and any lot coverage or floor-area rules. Then the permit itself: a second story is a full building permit with structural drawings stamped by an engineer, energy code compliance for the new envelope, and the full inspection sequence from footings to final. Separately, check your HOA's architectural rules if you have one; a covenant can be stricter than the city.
See also: Johnson County remodeling permits: what needs one and where to apply
Many remodels are built with the family in the house; a second story is the one where that often isn't possible for the whole schedule. With the roof off, the main-level ceilings open for structural work, and the stair being cut through, there's usually a stretch of weeks when the house isn't safely livable. Ask for the plan up front: which phases require moving out, how long, where belongings go, and how the main level is protected. Then put temporary housing and storage in the budget, because they're real costs of building up that building out rarely has.
Compare a second story against the alternatives with the same list of needs, not against nothing. A ground-floor addition, like BBD's Overland Park project, adds space with a new foundation and no stair, but it uses yard and it changes the roofline where it meets the house. Reworking the interior, or finishing a basement, adds usable rooms with no new envelope at all. The right answer depends on the lot, the house, and which rooms you actually need.
| Option | Adds | Costs you | Best when |
|---|---|---|---|
| Second story | Bedrooms and a bath without using yard | Structural work, a stair’s footprint downstairs, roof removal, likely moving out | The lot is tight and the yard matters |
| Ground-floor addition | Living space, a suite, or a bigger kitchen on one level | Yard, a new foundation, roofline and exterior matching | The lot has room and the need is on the main level |
| Rework the interior | Better rooms in the same footprint | The rooms you give up | The house is big enough and badly divided |
| Finish the basement | Bedrooms, bath, living space below | Egress windows, headroom checks, moisture work | The lower level is unfinished and dry |
See also: Overland Park room addition case study
Built by Design's previously published addition range is $150,000 to $550,000, and building up sits toward the top of it because it touches everything: engineering and structural reinforcement, the stair and the main-level work around it, roof removal and a new roof, a full exterior, new HVAC and often a panel upgrade, and temporary housing. A ground-floor addition of the same square footage skips the stair, the structural reinforcement, and usually the move-out. The addition cost page walks the scope decisions that move a project within the range; the second-story rows are the ones about building upward.
See also: What a home addition costs in Kansas City, by scope
Built by Design starts a second-story conversation the same way it starts every addition: an in-home visit where Mike and Kristen Schwartz walk the house and the lot, hear what the house no longer does, and look at the structure, the roof, and where a stair could land. From there the sequence is the structural evaluation, the layout on both floors, the city's height and setback check, and a written scope with selections before a price. Bring the address, any drawings, what's wrong today, and where you'd live during the work. You don't need a design to begin.
See also: Home additions with Built by Design
Built by Design meets homeowners at the home, writes one scope before finishes are chosen, and builds with the same trade partners named in the case studies above.
FAQAnswers, by design
The questions homeowners ask about adding a second story, answered from the residential code Johnson County cities adopt and the way an addition is actually planned. Your engineer and your city confirm what applies to your house.
Most can with reinforcement; a few can’t without foundation work that changes the math. A structural engineer evaluates the footings, foundation, bearing walls, and connections and produces the list of what has to be added: typically beams, posts, and footings where the new loads don’t line up with the old walls. Get that evaluation before the layout.
A code stair is 36 inches wide with 7¾-inch maximum risers and 10-inch minimum treads, plus landings. For a 9-foot floor-to-floor that’s about 14 risers and a straight run of 11 to 12 feet, so roughly a 3-by-14-foot slot through the main level, or a squarer footprint for an L or U shape. It comes out of a room, a hall, or a garage bay downstairs.
Usually not for the whole schedule. With the roof off, main-level ceilings open for structural work, and the stair being cut through, there’s typically a stretch of weeks when the house isn’t safely livable. Ask which phases require moving out and for how long, and budget temporary housing and storage.
Built by Design’s previously published addition range is $150,000 to $550,000, and building up sits toward the top of it because of the structural reinforcement, the stair, roof removal and a new roof, a full exterior, new HVAC, and temporary housing. A written scope after an in-home visit and a structural evaluation is what produces a real number.
For the same square footage, building out is usually less, because it skips the structural reinforcement, the stair, the roof removal, and the move-out. Building up wins when the lot can’t give up the yard, or when the need is bedrooms and a bath that belong on a separate floor. Compare both against the same list of rooms.
Not among the published case studies. The addition on this site is a roughly 1,000 square foot ground-floor addition in Overland Park, built in 16 recorded weeks. The second-story guidance here is the feasibility process BBD follows; the first in-home visit is where it gets applied to your house.
Keep planning with these related guides.
Budget & Costs
An addition can change how a house works for twenty years and still not return its full cost at sale. Here's how to keep those two questions separate, what an appraiser actually counts, and how to compare adding on with remodeling or moving.
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Johnson County Guides
Walls, wiring, plumbing, structure, additions, decks, and egress windows need a permit almost everywhere in Johnson County. Paint, flooring, and cabinet swaps usually don’t. Here’s the line, city by city, and what happens on the schedule.
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Basement Planning
Most Johnson County basement finishes need a permit, ceiling height and egress are the two code questions that shape the plan, and BBD basements have run $80,000 to $550,000 and 9 to 16 weeks of construction. Start here.
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