One story....you don't have to change anything, when your needs change. It provides more flexibility and less obstacles :)

manhattan42 -- At last! A definitive answer -- including the reasoning! Thank you.

In addition to the savings for smaller lots, I see why builders profit more selling multi-story homes (on smaller lots). The buyer sees more square feet of house. I see *stairs* and more difficult maintenance.

I grew up in a Georgian Colonial and lived in a townhouse for a few years. For the last forty-some years I have enjoyed single level homes. DH and I hope to continue in the current one until we need more assistance than we can get with home services.

Following. It's a worthy discussion.

Taller homes tend to have more maintenance with more windows and wall area exposed to blowing rain. Harder to re-paint and clean gutters.

Taller homes could be less efficient if they don't pay attention to air-sealing the ceiling/roof plane due to a stronger stack effect.

From Better Houses, Better Living by Myron E. Ferguson -- grammar mistakes are straight from the book, not my own creations -- I really think this guy knows his stuff, but he should've hired a ghost writer when he attempted to set it all to paper:

One story or two?

In deciding between a one- and two-story house, consider:

- Stairs

- Space taken by stairs and outside walls

- Heating and cooling

- Lot requirements

- Shading from roof overhangs

Stairs -- Older people, even those without physical disabilities, prefer not to have stairs. Two-story plans with the master bedroom on the first floor are helpful but most often single-floor arrangements are the choice of senior citizens.

Space taken by stairs -- A typical stairwell, including framing, is 4x13 feet, which is over 50 square feet on each floor of space that isn't needed in a one-story house. Landings also take away from useful floor area.

Outside walls -- The area on each floor taken up by outside walls is included in the stated square footage of the house. (Square footage is measured on the outside, not the inside, of a house.) With two floors this lost area occurs twice, once on each floor. In a typical 2400 square-foot house, the floor space taken by the walls will be about 40 square feet more for a two-story house than for a single-story with the same number of square feet.

Overall -- For the same amount of square footage the single-floor house will often be higher priced than a two-story unit. But don't assume that a two-story house is a better buy until you take out the floor space used by stairs, landings, and outside walls.

Heating and cooling -- As you know, upstairs rooms are noticeably warmer than downstairs areas. Most builders don't do anything about this even though there are ways to correct it. It will cost money and is another item to think about when comparing one- and two-story houses.

Lot requirements -- For the same amount of useful floor area, the two-story house takes up less of the lot. And in many areas the pressures for putting more houses in a given area are making lot sizes smaller and smaller. If this is the case where you are or if it is important to you otherwise, it may be the deciding factor in selecting your floor plan.

Shading -- Roof overhangs can be used to shade windows on one-story buildings but not the lower walls and windows of two-story houses. This can be important in the dessert and other hot climates -- which is why most houses in Arizona are one story. And every place, this lack of shade makes the summer cooling bill higher.

In FL, they built millions of single story block houses on slabs, and they were the cheapest of the cheap. Most of them had little or no insulation. A second floor would be unbearably hot. We once considered buying a lot and having a house built, and they wanted significantly more for a two story. The builder said that it cost a lot more to lay block for a two story, and that the insurance for roofing companies was a lot higher for two story work. I imagine it was mostly because the builder wasn't used to or geared up for two story houses.

I guess one story makes sense in places like FL that are hot, and have a very high percentage of retirees.

manhattan42 -- Does your opinion change on percentages, considering the *useable* square footage in the two-story that is reduced by the need for stairs, or were you going with appraised square footage?

The appraised square footage is based on the exterior measurement of all heated/cooled interiors, but the two-story loses living space to stairs. Homes with taller ceilings lose more space to the actual steps. More is lost if you don't want 'killer' (straight run) stairs. Living space is also lost areas that eixist only to give access to stairs.

Maybe the difference is less than 25% if we compare only *living spaces*?

The differential costs of one level vs 2 levels should not determine the organization of a house. The needs and desires of the owners, the siting and climate should be the important issues to consider.

There are many other decisions that will change the cost of the house far more than this decision so its a red herring and not worthy of serious debate.

I've read comments from several builders/architects who support what JDS says (although I don't think discussion is bad, people learn from it). The attached link is one example of
someone going through a very detailed analysis of his options building
in a restricted area. Deep in the article he looks into the cost of up
versus out. His architect told him that in her experience single-story
homes were less expensive to build. He talked to his GC who told him, "With a new single-story you might end up spending more on foundation and
roofing cost, but depending how it's designed, the production rate of
construction will be faster. A second-story might have more
construction challenges which will result in a slower production rate,
and perhaps deeper foundation and added cost of stairs. You might need
scaffolding or special equipment to deal with the height issues, but
overall, I'd have to say that new construction single-story and
second-story homes are comparable in price provided they have the same
quality finishes." This homeowner ended up going with a two-story, but not for cost reasons.

http://www.newpaloaltohouse.com/2012/03/mythbusters-edition-single-story-vs-two.html

A great thread. As a former member and chair of the Palo Alto Architectural Review Board, I can sympathize with the conclusion that, when it comes to cheaper up or out, it really does...DEPEND!

The thing is - when building a house the cheapest square footage is typically attic, followed by basement, then additional floors and finally the main floor. Since a second floor is always cheaper than the same first floor many people take this to mean that a two story is cheaper than a one story, but that is not what the above actually says. It just notes that adding an additional floor to a planned first floor will be cheaper than the first floor was, but it says nothing about comparing the cost to an entirely different first floor.

In general, additional floors are cheaper because the same roof and foundation are required and so those costs can be skipped as you add a floor. But two stories can require a larger area of exterior walls, which can destroy any savings on roofs and foundations.

For example, an 1800 square foot house that is 36' deep and 50' long will have 172 linear feet of walls and if the walls are 10' high, it will be 1720 square feet of exterior surface. Adding a second floor will double the exterior square footage to 3440. However, lengthening all walls to make it 48' deep and 75' long, will result in only 2460 square feet of exterior walls for more living space. If the exterior cladding and insulation is expensive enough then the extra exterior wall square footage will destroy any savings from roof and foundation.

In the end, how you add the square footage to a one story home is a bigger determining factor than just the square footage alone, so the comparison becomes impossible without further details.

A one story house can save quite a bit of exterior wall area compared to a two story house of the same floor area but that reduces the wall area available for windows and usually forces spaces like kitchens to be windowless interior spaces or that look over a dining space to windows. These plans are frequently posted on the GW. The addition of an attached garage reduces the wall area available for windows especially if it is recessed into the massing of the use due to a narrow lot.

The job of the house designer is to see these pitfalls and avoid them either by stretching a one story plan out and using connectors or courtyards or adding a second story. A good designer should be able to figure out what will work best from the initial site plan analysis and avoid the pain so often seen on the GW.

This issue should not be about money but livability. You could save a few thousand dollars but reduce the resale value by much more than that in addition to creating a dark house with a lot of corridors to access bedrooms.

JDS -- Your post about a one-story limiting windows interests me. Yes, you can only put windows on more than one side of a room at the 'ends' of the house, but isn't that true for a two-story? Maybe a brighter house is easier when it is smaller -- fewer 'inside' rooms?

We built a 2900 sq ft rectangle, two rooms deep. Rooms in the middle of the rectangle have big windows on their single exposures. Minimum 36" doorways let light spread. Our garage is at a 120-degree angle to the house and opens to the back hall -- window at one end and half-glass door at the other. Back hall opens between a breakfast room with French doors on two sides and the kitchen with a double-height wide archtop over the sink. The foyer door has a glass surround. Every room has natural light except secondary bathrooms and one 18 ft corridor that gets light from the three rooms it serves.

There is not only less wall area for windows but the strength of light from a window decreases by the square of the distance from the window. For equal sized houses the floor area within 10 ft of the exterior walls is much greater in a 2 story house making it potentially considerably brighter. Skylights can change that but are not always an acceptable substitute for windows from a psychological perception point of view.

Compare two 2,500 s.f. houses, one a single story and the other a two story. Make them square to make the math easy. The one story house will have 1,600 s.f. within 10 ft of the exterior walls and the two story will have 2,029 s.f. within 10 ft of the exterior walls. The two story house would have 17% more floor area within 10 ft of the exterior walls. That allows it to be brighter and provide a greater sense of the outside. Some ancillary spaces are fine in the center of a house but not living spaces.

As for the area of stairs in a two story house, a one story house has a similar space dedicated to an entry foyer and bedroom corridors.

On the other hand, people with disabilities need to be on one floor so other considerations are irrelevant. However, this issue can be usually be accommodated with a story and a half house.

PS

It is possible to configure a one story house so it will have as much space within 10 ft of the exterior walls by using wings and courtyards but that requires more land and increases the cost of the house. In short, in order to make a house as cheap as possible you will be forced to give up much of what makes a house great.

One story houses don't seem safe to me. If flooding is an issue, your bedrooms get wet. Your bedroom is at street level, where people can look in your windows. Plus it's easier to sleep when you are a story above anyone else awake and doing things, or any street activity.

But in a fire, I'd rather be in a one story house, or at least downstairs.

I don't know Ed. We are main floor master with the kids up and I can hear them walking around - and there is no living space above our bedroom.

No, the question of "Is It Cheaper to Build UP or OUT?" can't be settled.

Yes, this question is too general.

;-)

Lovely answers, everyone! Some say there's no answer. Yet some say the two-story is cheaper -- just not by what percentage. I'm happier with the convenience of one story -- for both young family and as a senior.

edlincoln -- I've been quite safe and dry in a a couple of one-story homes for over forty years. I like the one I live in now best, with a full basement where the mechanicals 'live'. Your water and safety questions have to do with location more than home style.

JDS -- Seems to me every house has an entry foyer, but a single-level needs no staircase. I understand the concept of more light, but can't that be compensated for by larger windows? (Windows that can more easily be kept clean!)

By now it should be clear: "Cheaper, up or out...?" is the wrong question, even if there was a definitive answer. Which there isn't, since there are so many variables and unknowns in the equation to solve for "x"! The better question is "Better, up or out--for my own living and personal needs?" What good is a cheaper x or y, if it really doesn't match your living and personal needs? Let us know how you solve your equation!

I asked because I prefer single-level and am continually told that is the more expensive choice -- but not why. I've already guessed that 'UP' is more profitable because that's what mass developers build -- perhaps not entirely due to putting more houses on less land.

I'd guess a buyer is thinking more along the lines of how many square feet he's getting than the utility of the footage. (This beyond 'preferences' for up or out.)

manhattan42 was able to make a like-like comparison. I wondered if the percentages were a bit high.