Before explaining how to read blueprints,
it may be valuable to understand what blueprints are. It is quite
difficult to build a structure to scale when the scale you are working
from is very small. To make things easier to read, architects and
designers complete their drawings on large scale vellum sheets of
various sizes; probably the most common sizes for residential structures
is 18" x 24" or 24" x 36". Twenty years ago,
we didn't have the technology that we do today where most plans
are drawn on computerized equipment. Plans were drawn by hand on
a semi-transparent film called vellum. Blueprints are made by overlaying
the vellum drawings on top of blueprint paper, which is then run
through the blueprint machine, which exposes the paper to intensified
light and ammonia. This exposure to ammonia and light causes the
blueprint paper to develop and the drawings are transposed in a
dark blue color.
The Vellum drawings were very valuable
since it represented hours and hours of work that the architect
put in to creating the drawing. These days, house plans are most
commonly created using computer aided drafting software. Once complete,
the drawings are plotted (printed) on a large-scale printer called
a plotter. If the vellums are accidentally destroyed the architect
has the plans on file to re-plot. As consumers often have minor
changes to personalize their home plan, vellums are quite commonly
purchased rather than a package of blueprints. Consumers can then
draw any changes onto the vellums before making Photostats or blueprints.
Vellums generally cost more since it gives the consumer the opportunity
to make as many blueprints as desired for a single construction.
Home plans are drawn to scale
so that if any specific dimension needed is missing, the contractor
can scale the drawing to determine the right measurement. The main
floor plans are generally drawn to ¼" scale which means
that every ¼" on the plan equals 1' in actual length.
Other details like framing layouts or built-in details may be drawn
at another scale like 1/8" or even ¾". The scale
of each drawing is usually called out beneath the drawing or somewhere
on the page, usually next to the title.
Elevations are a non-perspective
view of the home. These are drawn to scale so that measurements
can be taken for any aspect necessary. Plans include front, rear
and both side elevations. The elevations specify ridge heights,
the positioning of the final grade of the lot, exterior finishes,
roof pitches and other details that are necessary to give the home
its exterior architectural styling.
The basement or
foundation plan delineates the location of bearing walls that will
support the structure. It also identifies locations of footings,
steel (rebar) placement, hurricane strap placement and other structural
elements that are required to support the loads of the upper floors.
Floor plans are actually quite easy to understand. A floor plan
layout on blueprints is basically an overhead view of the completed
house. You'll see parallel lines that scale at whatever width the
walls are required to be. Dimensions are usually drawn between the
walls to specify room sizes and wall lengths. You'll also see on
the floor plan locations of fixtures like sinks, water heaters,
furnaces, etc. Among the walls and dimensions you will often find
notes to specify finishes, construction methods, or even symbols
for electrical or to reference cross sections.
are sometimes on a separate page to make reading them a little easier.
The layout will show locations of light fixtures, fans, outlets,
light switches etc. There is usually a legend on the page which
explains what each symbols represents. For illustration purposes
we have included such a legend below. There may be such legends
for heating systems, door swings and sizes, or even to specify certain
The framing drawings
are also drawn to scale and outline the layouts of items such as
floor joists and trusses, beam locations and other structural requirements.
Framing layouts don't usually get into the details of each stud
location in the walls since framing contractors are required to
follow certain rules and regulations to assure that the home meets
the required building code specifications. Though there are often
cross section within the plan pages that outline the general methods
of wall construction or floor assembly.
These systems are generally
not covered extensively on the blueprints other than locations of
fixtures and main service lines. If you are going to the expense
of more complicated heating systems like in floor radiant heat or
even an engineered forced air system, these drawings need to be
completed by a heating or plumbing specialist.
Overhead views or floor plan views of the structure
don't always provide enough information on how the home is to be
built. Often times cross section or details will explain certain
special conditions more appropriately. A cross section is basically
a view of the home if it were sliced down the center. This allows
you to view the home from the side and understand a little better
the relativity of varying floor heights, rafter lengths, and other
Plot Plans are drawn to determine
the placement of the home on the building lot. A plot plan again
is an overhead view of the construction site and the home as it
sits in reference to the boundries of the lot. Stock house plans
usually do not include plot plans since they are drawn specific
to the site where it will be built. Plot plans can be drawn by a
local professional draftsman, architect or engineer. Plot plans
should outline location of utility services, setback requirements,
easements, location of drives and walks, and sometimes even topographical
data that specifies the slope of the terrain.
These are the basics of reading a
house plan; keep in mind however that what is included in plans
will vary according to the designer who drew them. House plans are
a very important part of the homebuilding process. It is crucial
to purchase a plan drawn by a home design professional since they
have a thorough understanding of how homes are built. If there were
any terms on this page that you did not understand or would like
a more thorough description of their meaning, please visit our construction