When comparing house plans, one of the most important features you will consider is the zone of the floor plan – the size of the floor plan – measured in square feet.
But I will tell you a little secret about “square footage”: it is not measured in the same way on every floor plan of the house. That means that two house plans that appear to have the same area may not actually be.
Does that make much of a difference when choosing a plan? For sure YES! A mere 10% difference on a 3,000 square foot plan could unexpectedly cost you tens of thousands of dollars!
Apples to apples
Builders, architects, real estate professionals, bankers, auditors, and appraisers often count square footage differently, to better meet their particular needs. Home plan services also vary in their area calculation protocols; To accurately compare the areas of the floor plans, you must ensure that the areas are counted in the same way.
Generally, builders and real estate professionals want to show that a house is as big as possible; allowing them to quote a lower “cost per square foot” and making the home appear more valuable.
County appraisers and auditors generally measure the perimeter of the home, a typically very rough way of calculating area, and call it a day, while architects break size down into components; first floor, second floor, porches, finished lower level, etc.
To come up with an “apples-to-apples” comparison of home areas, you need to know what is included in the totals. Does the area include only heated and cooled spaces? Does it include everything “indoors” (I’ve seen garages in some areas of the plan!) Or just “living space”?
Up and down, inside and out
But even when you’ve figured out exactly which spaces are included in the area calculation, you’ll need to know how volume is counted, and if the total is net square feet or stupid.
The gross area is the total of everything that is inside the outer edge of the perimeter of the house; the net area is the same total, minus the thickness of the walls. In other words, the net square footage is the part of the floor that you can walk on; the gross includes the parts it cannot walk on.
The difference between the two can be up to ten percent, depending on the writes of the floor plan design. A “traditional” plan (with more different rooms and therefore more walls) may have a net / gross ratio of ten percent, while a contemporary plan may have only six or seven percent.
Likewise, bigger houses tend to have more walls, because bigger houses generally have more rooms, rather than just bigger rooms.
You will probably never see the volume of a house plan listed on a plan site, but the number that represents the area of a floor plan often depends on how the volume is counted. Generally, the “upper area” of two-story rooms (foyers, family rooms) is not counted as part of the floor plan. Also, stairs are only counted once. But not always – check how volume is counted to make sure you know how big the plan really is.
Plan services that design their own plans will have a consistent policy on area (and volume), but services that sell plans on consignment probably will not.
How does the designer or service of the plan you are buying from calculate the size of the plan? Sometimes that information is found on the service’s website or book, and sometimes you need to call them to find out. But you should definitely find out – it can make a huge difference in the cost of the house you will eventually build!
