Building Costs: Single- vs. Two-Story Construction
Michaelluscri
| Posted in General Questions on
Is it cheaper to build a two-story house versus a one story house on a per square foot basis?
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Replies
Michael,
Typically, yes. A two story plan would be a bit cheaper per square foot because the second floor is generally occupying the same footprint with equivalent foundation and roof area.
Smaller foundation and a smaller roof. However you lose floor space to stairs, which are typically a higher priced millwork item, have more difficult circulation, and during the build have to work off scaffolding or ladder-jacks.
An interesting question would be whether comparable houses built each way were worth the same when sold.
I worded that poorly. Yes, less roof and less foundation to hit the same square footage. If the building form is simplified and overall exterior surface area is reduced, which is usually the case going to two-story, I stand by the small cost/SF reduction. Buyers in the Midwest prefer single story over basements or walkouts but the real estate agents count square footage above grade all the same.
Jason,
My reply was poorly word too. I agree, in theory, in most cases an apples to apples house would usually be cheaper to build if it were two storey - although i've never managed to realize those possible savings. Once you factor all the other variables which affect cost, the difference isn't significant enough to use as a determinant of which way to go. In those types of situations, where any gains are at best marginal, the choice should be determined by architectural, considerations, owner preferences, or those dictated by the site.
Michael,
I have built lots of both and have never been able to differentiate between the two on a cost basis. There are certainly circumstances when one could cost more than another, but my experience has been that it isn't worth making the design decision based on the number of stories, unless there is something about the site or style of the proposed house that would definitely drive some difference.
So far, from the discussion by people more knowledgeable than I, it seems like the cost is a wash. As far as green attributes, the reduced amount of concrete in a two-story building would make it better on up-front emissions; possibly also a reduction in the amount of land that needs to be cleared, if there's potential to leave trees standing. At first glance, it would seem that a two-story building, being closer to a cube, would be more favorable from an energy use perspective, but the added roof area doesn't hurt much, given that it's inexpensive to put high R-value insulation in a vented attic floor, and the floor area doesn't hurt much since the earth isn't nearly as cold as the outdoors in winter. And the wall area can actually be less for a give floor area in a single-story building.
The comparison also depends on size. In a small building, the area penalty for including stairs is more than in a large building.
You can eliminate concrete altogether and use helical piers. Piers aren't cheap but they are very green. Of course a larger footprint = more piers = more $$, just like concrete.
We are going 1 storey. After adding up the framing for the second floor, finished flooring, stairs, railings, ceiling finishes, hallways versus none of those things but some extra exterior walls and roof? Easy decision. Managed to design it with only 4' of hallway so no space is wasted.
One other consideration - the amount of wall square footage will generally be greater for any given amount of floor space with a two-story house as opposed to single story - therefor two-story houses are generally, inherently less energy efficient than single story - this may or may not be a consideration depending on climate, budget, house shape, and other factors - but, the energy loss can be calculated if of interest.
Also will be potentially easier to heat a 2-story house of a square or rectangle dimension compared to equal square footage single story.
But building a two story house is not easy or fun IMHO. Too much ladder and scaffold time. More risk of serious injury.
We wanted to build a bungalow but also ended up with a bunch of dead or wasted space without starting to add a bunch of bump outs. We wanted to keep the shape of the house simple for cost and energy efficiency purpose but also to make it easier to build.
Arnold