Square Footage and Dimensions
When you buy a set of blueprints for a home, you get hundreds of
dimensions and thousands of details. Before you buy the blueprints, you
look at simplified “house plans” that give overall information about
the blueprint. The house plans give you general information such as square
footage and overall dimensions.
In this article, when we talk about rounding or approximations we are
referring to the floor plans you see before you buy blueprints and not the
actual details found on the blueprints.
A house plan's square footage tells you how many square feet of finished
space a plan occupies. The finished space is the heated area of the home.
Finished space usually has floor coverings such as wood, vinyl, ceramic,
Unfinished areas such as garages, porches, decks, attics, courtyards, and
driveways are not included as part of the finished square footage of a
plan. A basement is not included in the finished square footage unless the
basement is finished. A 3-season porch is not considered finished square
footage because it is not heated space.
Unfinished bonus rooms (such as a room over a garage) are not considered
finished square footage. However if you finish the bonus space then it can
be considered finished square footage. On our website we sometimes give a
minimum and maximum square footage range for a floor. The minimum square
footage shows the size of the floor if the bonus space is not finished.
The maximum square footage shows the size if the bonus space is finished.
Square footage is not the same as the floor space. Typically the square
footage is calculated by using the dimensions starting from the outside
studs of the home’s exterior. The square footage doesn’t include
exterior wall coverings such as brick, stucco or siding. The square
footage does include space that is taken up by walls.
For example if the outside dimensions of a one story home are 20 foot by
50 foot then the home has a square footage of 1000. In this example, if
the home's walls are 4 inches thick then about 47 square feet of the
square footage is used up by the thickness of the exterior walls.
Therefore, of the 1000 finished square feet in this home only around 953
feet of interior space exists and the exterior walls take up the rest of
the "finished" space.
Cantilevered floors also affect square footage. A cantilevered
(overhanging) room such as a bay window is counted as finished square
footage if the floor joists are part of the cantilever. If a cantilevered
space does not include floor space (such as boxed window) then the
cantilevered area is not counted as part of the square footage. If a
fireplace cantilevers then the square footage of the cantilever is counted
as finished square footage on the floor that has the fireplace but not on
For stairways in a two-story home, usually the space occupied by the
staircase is counted once when calculating square footages. However a few
designers or builders consider a stairway transitional space and sometimes
count it as square footage on both floors. The floor space of an interior
balcony or loft is included in square footage calculations.
If you are comparing two plans that have the "same" finished
square footage you may want to remember that wall space is part of the
square footage. For example, if you see a one story home that has the same
finished square footage as a two-story home, then the one story home will
actually have more interior space. This is because the two-story home has
another floor of exterior walls that are considered part of its square
footage. Also a two-story home needs more space for hallways and stairways
and the useable square footage of a two-story home is usually less when
compared to a one-story home that has the same square footage.
Square footage does not include any area on a level where a floor has not
been built. For example, if a two-story home has a family room with a
two-story ceiling then the square footage of the main floor would include
the family room space. However, on the second floor there is no useable
floor space over the family room and there is just airspace. Therefore on
the second floor the family room's square footage would not be counted as
part of the square footage for the second floor.
A low ceiling can also reduce the finished square footage of a room. The
parts of a room where the ceiling is less than 5 feet tall do not count as
finished square footage. Also, typically at least 50% of a room needs to
have a minimum ceiling height of 7 feet for the room to count as finished
space. This guideline is usually used for tax or real estate purposes, but
some builders or designers may consider areas with low ceilings as
finished square footage if the room is finished.
On floor plans, the width is usually shown first and the depth is shown
next. For example if a room dimension is shown as 10’ x 12’ then the
width is 10 feet and the depth is 12 feet. “Width” means measurements
going from side to side. “Depth” means measurements going from the
front to the back of the home.
When a floor plan gives the dimensions of a room, it shows the interior
dimensions. Room dimensions are measured from interior wall to interior
wall and are usually the same as the floor covering dimensions. However,
in some rooms the room dimensions are larger than the floor space
dimensions. For example kitchens and bathrooms have built in cabinets and
fixtures that take up floor space. Other rooms such as the great room may
also have built-in bookshelves or cabinets that take up floor space.
Closet space is usually not included in a room’s dimensions.
House plan companies usually show room dimensions in feet and inches and
the square footage dimensions to the nearest foot. Usually the room size
given indicates the distance from one interior wall of the room to the
interior room on the opposite side of the room. However, some designers
describe floor plans by measuring from the middle of the wall stud. Some
designers also round off the room size. Therefore the room size dimensions
given on a floor plan may be around 4 to 6 inches different then the
actual interior room dimensions given on the blueprint. Sometimes
designers do this to discourage illegal usage of the floor plans and when
you buy the blueprints you will get the exact dimensions on the
If a room is not a traditional square or rectangular room such as a room
that has angles or curves, then it is difficult to note room dimensions.
In these cases the room dimension on the plan usually gives an overall
rectangular dimension. For an unusually shaped room, the blueprints will
give much more detailed dimensions to properly represent the room.
Most house plans show only ceiling heights that are different from the
primary ceiling height of other ceilings on the same floor. For example,
if the main floor has a ceiling height of 9 feet, then typically only
rooms that are not 9 feet tall will have a ceiling height shown on the
floor plan. When a ceiling height is shown it usually describes the
highest point the ceiling reaches in the room. For example if a room has a
cathedral ceiling then the ceiling height describes the height of the
ceiling at the peak of the ceiling.
When giving width and depth dimensions for a home’s footprint, usually
the width and depth is based on the exterior walls of the home. Roof
overhangs or structures without a roof are typically not included in the
overall width and depth dimension. For example, decks, exterior steps,
gates, and fences are usually not included when describing the footprint
size of the home.
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