One Story vs 1.5 Story: Which to Build and Why
Choosing between a one story house and a 1.5 story house is one of the first big decisions you'll make before you ever pick a floor plan. It shapes your budget, your build timeline, and how the house will actually feel to live in for the next twenty or thirty years. At Home Plan DIY, it is one of the questions we hear most from owner-builders who are comparing plans, so here is a clear, practical breakdown of what each option really means.
What "1.5 Story" Actually Means
A one story house puts every room, bedrooms included, on a single level. There are no stairs to navigate day to day, and the roof and foundation cover exactly the footprint you're living in.
A 1.5 story house has a full main floor plus a partial upper level, usually built into the roofline with dormers or gable windows to bring in light and headroom. That upper level often holds a loft, a bonus room, or one or two secondary bedrooms, while the primary suite and main living space stay on the ground floor. If a plan we sell includes this kind of upper space, we always describe it as 1.5 story rather than a full second story, because the upstairs square footage is smaller and shaped by the roof pitch, not a flat, full-size floor.
Cost: What Actually Drives the Number
Build cost for both styles typically falls in the $130 to $220 per heated square foot range, depending on your region, finish level, and site conditions. For a 1,800 heated square foot home, that works out to roughly $234,000 to $396,000 total, regardless of whether that square footage is arranged as one story or 1.5 stories.
Where the styles actually diverge is in what drives the cost within that range. A one story home needs a foundation and roof sized for the entire living area, which is straightforward to build but uses more material per square foot of usable space. A 1.5 story home needs a smaller foundation and roof footprint for the same heated area, but the upper level requires steeper roof framing, dormers, and more detailed stick-framed construction, which adds labor. In practice, many owner-builders find the two styles land in a similar place on cost, so the decision usually comes down to lot size and how you want to live, not a guaranteed dollar savings either way.
One Story: Pros and Cons
The biggest advantage of a one story house is simplicity, both to build and to live in. There are no stairs, which matters a lot if you're planning to stay in the home long term or want it to work for aging parents or young kids. Maintenance is easier too. Gutters, roof repairs, and window washing all happen at a lower height.
The tradeoff is that a one story house needs a larger footprint for the same square footage, which means it needs a wider lot. If your land is narrow or you're working around setbacks, a sprawling one story plan may not fit without redesign.
1.5 Story: Pros and Cons
A 1.5 story house lets you get more living space on a smaller footprint, which is a real advantage on narrow lots or when you want to keep site work and foundation costs contained. The upstairs loft or bonus room is also flexible. It can start as a guest room or home office and later become a bedroom as your family grows, without adding on to the house.
The downside is that the upstairs space is shaped by the roofline, so ceiling height near the walls is limited, and not every square foot up there is fully usable. You'll also have at least one staircase, which is worth thinking through if aging in place matters to you.
Roof Pitch and Lot Fit
Roof pitch matters more for 1.5 story homes than most owner-builders expect going in. A steeper pitch, generally 8:12 or higher, gives you more headroom and usable floor space upstairs, but it also adds material and labor cost and may need to meet specific wind or snow load requirements depending on where you're building. If you're drawn to a 1.5 story plan, it's worth checking the roof pitch called out on the plan and confirming it works with your local building code before you commit to a lot.
Lot shape plays a role too. A one story plan generally wants a wider, more open lot to spread out on, while a 1.5 story plan is a natural fit for narrower lots, infill sites, or land where you want to preserve yard space.
Which One Should You Build?
If your priority is single-level living, easy long-term maintenance, and you have a lot with room to spread out, a one story house is usually the more straightforward build. If you're working with a smaller or narrower lot, want a flexible bonus space that can grow with your family, or like the look of dormers and a more vertical roofline, a 1.5 story plan is worth a closer look.
Our Single-Story House Plans collection is a good place to start comparing layouts if single-level living is your priority. For a real-world look at how a 1.5 story loft space comes together, our Modern A-Frame Cabin Plan with Loft shows how a compact footprint can hold a full loft bedroom upstairs, while our 2 Bedroom Single-Story House Plan shows the same living area laid out entirely on one level.
Every plan we sell includes a full PDF drawing set plus a material list, so you have what you need to price the build and get permits, with editable CAD files available as a paid add-on if your builder needs them. If you're weighing square footage against budget more broadly, our recent post on tiny house plans under 800 square feet walks through the same cost-per-square-foot approach at a smaller scale.
Frequently Asked Questions
Is a 1.5 story house cheaper to build than a one story house?
Not necessarily. Both typically fall in the $130 to $220 per heated square foot range. A 1.5 story home needs a smaller foundation but more complex roof framing, so the two styles often land in a similar overall range once you calculate the total for your square footage.
Can a 1.5 story loft be used as a full bedroom?
Often, yes, as long as it meets local code for ceiling height, egress windows, and square footage. Check the specific plan's dimensions and your local building code before assuming a loft counts as a legal bedroom.
Does a 1.5 story house need a steeper roof?
Usually. A pitch of 8:12 or higher is common on 1.5 story designs because it creates enough headroom upstairs to make the space usable. Lower pitches can leave you with a loft that's more crawl space than living space.
Which style is better for aging in place?
A one story house is generally the better fit if single-level living long term is a priority, since it removes stairs from daily life entirely.
What's included when I buy a plan from Home Plan DIY?
Every plan comes with a PDF drawing set and a material list. Editable CAD files are available as a paid add-on for buyers who need them for a builder or engineer review.
