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How to Read House Plans

by Don Vandervort, © HomeTips

Before you can get a building permit or contractor bids for a remodel, you’ll need a set of house plans (also called working drawings or blueprints). House plans document and communicate every facet of the construction project to the homeowner, contractor, subcontractors, financial institution, and city building department. They are intended to ensure that everybody is literally “on the same page.” As discussed in How Architects & Designers Can Help, these are the work of design professionals.

As the homeowner, it’s important for you to know how to read these drawings so you understand the designer’s intentions, can make sure the construction is done properly, and can minimize disputes with the contractor.

House Plan Basics

Scale is used to reduce dimensions in drawings to a manageable proportion. Most blueprints are drawn so that 1/8 inch, 1/4 inch, or 1/2 inch equals 1 foot. Symbols are used to reduce the amount of description needed. A 1-foot architectural scale ruler is the tool you’ll need for easily scaling dimensions so you can study furniture layouts and the like.

A typical set of drawings for a remodel consists of floor plans that include plumbing and electrical layouts; elevation and section drawings; and structural plans. Drawings may also include HVAC and reflected ceiling plans. If the remodel involves expanding beyond the home’s existing footprint, the drawings will also include a site plan, foundation plan, and roof plan.

Floor Plans

Despite its name, the floor plan is much more than a plan of the floor. It’s a bird’s-eye view of the floors, walls, doors, windows, stairs, counters, built-ins, and other key elements. It shows the sizes of all rooms and spaces, the direction of door swings, the location of plumbing fixtures, and more. In addition, it usually includes the locations of lighting elements, switches, and other electrical devices, although more-detailed drawings of the electrical system are often done separately. A separate plan is done for each floor.

A floor plan is keyed to specifications and other drawings using symbols. Dimension lines, or stringers, specify all dimensions and are notated in feet or inches. Stairs are shown as a sequence of treads; an arrow indicates the direction—up for an incline, down for a decline. A door is specified by a symbol on the legend. The door’s direction of swing is shown with an arc.

Section lines and references indicate the point at which a cross section is taken for an elevation/section view. Like an arrow, they point to the direction of the view; letters and numbers on them tell you where to find the referred drawing. The letter or number on the top is the section, and the number on the bottom is the page.

Other numbers or letters in circles or hexagons refer to a materials schedule that contains complete descriptions of each building material, including any manufacturers’ specifications, and the quantity of each item. Notes also call out structural requirements.

A plan view is almost always oriented with “project north” at the top of the page. Project north may vary from magnetic north; it’s an approximation based on lot lines, streets, and so on. An on-page compass designates north and, where solar orientation is critical, true magnetic north.

Elevation & Section Drawings

Elevation and section drawings are different from floor plans in that they reveal the vertical—not the horizontal—elements of a house. These drawings show walls and roofs from a straight-on perspective.

Elevation and section drawings each serve a particular purpose. An elevation shows construction from a full frontal view, with outer coverings, trim, doors, windows, and so on. A section view peels away the coverings, taking a slice through the structure at a given point, which is specified on the floor plan, to see how the construction works. Such a view typically is taken through the center of a house to show how various floor levels interrelate.

In a full set of architectural drawings, elevations are given for the front, back, and both sides of the building. These may be labeled Front, Back, Left Side, and Right Side, or, more typically, by compass directions North, South, East, and West. Examining the elevations will give you a better idea of what a house will look like.

Like floor plans and other architectural drawings, elevations are noted with the scale, dimensions, materials, building instructions, symbols for specifications, references to other drawings, and so forth.

Interior elevations are drawn for key walls, such as those that are fitted with cabinets, stairs, or similar details. They are also used to show how windows and doors are seen from inside a room.

An exterior elevation includes windows, doors, siding, steps, chimneys, roof, and all other details you would see from that view. Standard graphics are used to designate common building materials such as wood siding, brick, and stone. These graphics are indicated on the symbol legend.

Where very specific dimensions or structural detailing are needed, section views are drawn. Sections are typically taken through the center of a house to show how various floor levels interrelate. A section view slices the house to reveal interior construction details. The location of this slice is called out on the floor plan and may be referenced on other drawings as well. Because section drawings are technical documents needed for construction, they usually include extensive building instructions and detailed dimensions.

Electrical Notations & Plans

An electrical plan may or may not be included as a separate sheet in a full set of architectural drawings; in many cases, this information is supplied on the main floor plans. A separate electrical plan, however, is a little easier to work with because it isn’t cluttered with all the other construction information. The electrical plan illustrates a home’s electrical lighting, switches, receptacles, phone jacks, doorbells, cable television jacks, and similar electrical devices.

Be aware that building codes, such as the National Electrical Code, set basic standards regarding the types of devices and wiring that may be used, as well as their appropriate locations. For example, code requires that every usable wall must have an electrical outlet no further than 6 feet from any point along that wall (in most cases, this means outlets are spaced 12 feet apart).

Electrical outlets are designated on an electrical plan by various architectural symbols. A split-wired convenience outlet, like a normal duplex receptacle, has two places to plug in lamps or appliances. One of the two is controlled by a wall switch. A weatherproof outlet is required outdoors. A ground-fault interrupter, which shuts off the circuit instantly if there is a short, is required in bathrooms, kitchens, and porches.

Switches, also available in several varieties, are designated by symbols that specify single-pole, three-way, four-way, dimmer, and weatherproof models.

Lighting is called out by a symbol that’s often connected by a dotted line to the switch that controls it. These dotted lines don’t necessarily show the actual path of the wires. Fluorescent fixtures have slightly different symbols.

Other devices called out on an electrical plan include thermostats, humidistats, doorbells, fans, chimes and buzzers, and telephones.

Site Plans

If your remodel will involve expanding the footprint of your house, the city building department may also require a site plan, which shows the shape, dimensions, and contours of a particular site and where the house and other structures on the property are (or will be) located. A site plan includes property lines, setbacks, utilities, drainage, sewer or septic lines, and a bird’s-eye view of the “footprint” of the buildings. A site plan also shows trees and may even include circular drip lines around them that indicate the root spread so roots can be avoided during excavation.

Perhaps the most confusing parts of a site plan are the contour lines, the wavy lines that show variations in grade. What’s important to know is that between each two lines the ground rises or drops 1 foot. This means that where the contour lines are close together, the site is hilly or steep; where they are far apart, it’s flatter.

A site plan utilizes the same types of symbols as a floor plan to reference other drawings and details.

To get free recommendations for top-rated local architects, call the most reliable and comprehensive referral service, HomeAdvisor, at 866-350-2983 (toll free).

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