Understanding Construction Drawings: Guide for Contractors (2024)

Reading construction drawings is an essential skill for the construction professional. But you need to know more than just how to read the plans — you need to know how to sift through all the detailed information find what you need quickly.

We’re going to walk through everything you need to read construction plans quickly and efficiently.

Key Takeaways

• The construction drawings show how the parts and pieces of a building fit together.
• Understanding the contents of the construction plan drawings and how they are organized allows you to find needed information quickly.

What are Construction Drawings?

Construction drawings are a part of the construction documents that serve as a comprehensive guide to the owner and architect’s design intent for the construction project. They are a graphical representation of the building or the project and are often called blueprints because, historically, they were blue and white. They show the locations of the walls, roof, doors, windows, and other building components and how they fit together. For instance, you would look at the drawings if you wanted to know where the rebar was located.

The Design Process for Construction

The design process for buildings is led by an architectural firm, which puts together a design team. This team is made up of several consultants who assist with the design, often including a landscape architect, an interior designer, and civil, mechanical, electrical, and structural engineers. On some projects, the GC is hired as a construction manager during the design process to address cost, schedule, and constructability issues. Typically, the architect works for the owner; however, in a design-build contract, they work for the GC.

Historically, construction drawings have been drawn in two dimensions using software like Autodesk’s AutoCAD®. Drawing them in three dimensions using Building Information Modeling (BIM) software like Autodesk’s Revit is becoming more common. Drawing the building in three dimensions helps catch more errors, like having two building components occupy the same space, much easier.

The drawings for buildings typically pass through the following stages:

1. Schematic Design

The schematic design establishes the criteria that the building’s design needs to meet. In this stage, the architect works with the stakeholders to establish the building’s requirements, like the number and type of rooms, space allocation for each room, and the relationship between the rooms. This is referred to as “programming”. Additionally, how the building is situated on the site, its size, footprint, number of floors, and overall shape are established here.

2. Design Development

The building’s design begins to take shape during the design development stage. The programming requirements are developed into workable floor plans that define the rooms. Preliminary designs for the exterior and interior elevations are prepared to show the building’s overall aesthetics. Building and wall sections are developed, elevations for key interior features are designed, and types of finishes are identified.

Design development is a time when various design options are explored. When GCs are involved in the design process, they prepare cost estimates for competing designs, assess constructability, and provide other construction-related information (like material availability) needed to evaluate the designs.

3. Construction Documents

During this phase, the construction documents needed to obtain all approvals and bids on the project are prepared. This includes the final set of construction drawings, bid documents, contracts, and technical specifications. The design team should verify that the design meets zoning and building codes and may submit the drawings to the local building department for plan review before the construction process begins.

Different Types of Construction Drawings

Several different types of drawings are used to show how the building is constructed. Let’s talk about the various types of drawings you are likely to encounter.

Plan Views

Plan views are drawn from an overhead perspective and show the spatial layout of the building or construction site. A building’s plan view shows what you would see if you took a saw and cut the top of the building off at a height of about four feet. If you wanted to find a room’s horizontal dimensions, you would look at a plan view.

Elevations

The elevation drawings show the vertical surfaces of a building, providing the vertical and one of the horizontal dimensions of the surface. They are used to communicate the heights and architectural features on the surface. Elevations are commonly used to show the building’s exterior and key interior walls, such as kitchen and bathroom walls. Elevation markers on the plans indicate the elevation where you will find information about the surface they point to. For instance, if you wanted to find the mounting height of a fire extinguisher cabinet, you would look at an elevation.

Sections

The section drawings show the construction of individual building components as if you cut vertically through them and looked at their interior details. Construction drawings typically contain sections throughout the entire building showing the relationship between the foundation, floor, walls, and roof. Additional sections are provided for the individual walls. Cutting plane lines (a line with a dash and two dots) on the floor plans indicate the section where you will find information for the building or wall. For example, if you wanted to find the framing material for a wall, you would look at a section.

Details

Construction detail drawings provide a close-up view of building components, showing small dimensions and details that can’t be shown on the plan views, elevations, and sections. Details may be drawn in plan (from above) or section view. Cutting plane lines and reference marks on the plan views, elevations, and sections indicate the details where you will find more information about the component. For example, if you wanted to see the anchor bolt spacing for a column, you would look at a detail.

Schedules

Schedules are tables that list information about a specific class of building components, like doors, finishes, plumbing fixtures, and HVAC equipment. For example, a fixture schedule would show each fixture’s manufacturer, model number, and other pertinent information. A reference mark on the plans or elevations indicates the row on the schedule where you would find information about the building components.

Isometrics

Isometric drawings show 3D relationships for building components, like how the plumbing pipes are connected between floors. In an isometric drawing, the horizontal axis is drawn at a 30-degree angle from the horizontal, with one horizontal direction shown up and to the right and the other up and left. The vertical axis is drawn vertically. The components (like pipes) are often drawn using a single line.

Drawings Scale

The blueprints are often drawn to a reduced scale. For example, a 1/4″=1′ scale would be drawn where a quarter inch on the plans was equal to one foot in the building. Make sure you check the drawing’s scale when you read blueprints.

How Construction Drawings are Organized

All your construction team members need to understand how construction drawings are organized so that they can find information quickly. Let’s walk through how a typical set of construction drawings is usually arranged.

Cover Sheets

The cover sheets provide general information about the project. Often, the number of these drawings begins with a “G” for general. The following information is commonly found in these sheets:

• Title page with the project’s name, number, location, and contact information for the owners and designers.
• Index of drawings included in the set.
• Approval page for sign-off by the owners, the architect, engineers, and regulatory agencies (such as the planning and building departments).
• A boundary survey for the property.
• General notes, symbols, and abbreviations that apply to all the drawings.

Civil and Site Drawings

The civil and site drawings show the location of the building on the property and the construction of the site improvements. Often, the numbering of these drawings begins with a “C” for civil or “L” for landscaping. These drawings commonly contain:

• General notes, symbols, and abbreviations that apply only to the civil and site drawings.
• Site plans that show the locations of parking lots, sidewalks, patios, and other site improvements.
• Grading plans that show the existing and proposed contours of the site.
• Utility plans showing the construction of the site utilities, including sanitary sewer, water, gas, electrical, and communications.
• Stormwater plans showing the on-site features (like swells, gutters, and detention ponds) used to manage stormwater and drainage systems for transporting the stormwater off-site.
• Landscaping plans showing the design of the landscaping and irrigation system.
• Sections, details, and schedule for each of the plan views. They may be located with their plan views or at the end of the civil section.

Architectural Drawings

The architect prepares the architectural drawings which define the look and function of the building. Often, the numbering of these drawings begins with an “A” for architecture. In general, the drawings are organized as follows:

• General notes, symbols, and abbreviations that apply only to the architectural drawings.
• Floor plans for each of the building’s floors, showing the location of the walls, doors, windows, cabinetry, etc. These may include floor plans showing furniture and equipment layouts.
• Roof plans showing the design and slope of the roof.
• Exterior elevations showing the finish of the exterior walls.
• Building sections showing the construction of the floors, walls, and roof.
• Reflected ceiling plans showing the ceiling construction, such as the acoustical grid and tiles layout. These plans are drawn as if a mirror were placed on the floor so that the ceiling plans have the same orientation as the floor plans.
• Finish plans and schedules, which include critical interior elevations; enlarge floor plans for areas with lots of details (such as kitchens and bathrooms); door and window schedules; and finish schedule for the floors, walls, and ceilings.
• Sections and details (such as cabinets and stairs) for the architectural drawings.

Structural Drawings

The structural engineer prepares the structural drawings which show the design of the building’s supporting structural elements. Often, the numbering of these drawings begins with a “S” for structural. They typically include the following:

• General notes, symbols, and abbreviations for the structural drawings.
• Foundation plans showing the construction of the lower portion of the building that supports the building and transfers its weight to the soil.
• Framing plans for the weight-bearing members (like studs, columns, beams, joists, trusses) used to construct the building’s walls, floors, ceilings, and roof.
• Sections and details (such as base plates and connections) for the structural drawings.

Fire Sprinkler Drawings

The fire sprinkler drawings show the design of the automatic fire sprinkler system. Often, the numbering of these drawings begins with an “F” for fire sprinkler. These drawings include the following:

• General notes, symbols, and abbreviations for the fire sprinkler drawings.
• Fire sprinkler plans for each of the building’s floors.
• Riser diagram showing vertical piping of the fire sprinklers.
• Sections, details, and schedules for the fire sprinkler system.

Plumbing Drawings

The mechanical engineer prepares the plumbing drawings which show the design of the water supply system, the drain and waste systems, roof drains, gas piping, and other related system. Often, the numbering of these drawings begins with a “P” for plumbing. These are a part of what can be referred to as “MEP drawings” which are all your mechanical, electrical, and plumbing drawings. Plumbing drawings include the following:

• General notes, symbols, and abbreviations for the plumbing drawings.
• Water supply and waste plans, riser pipe diagrams, and isometrics showing the water, drain, waste, and vent piping layouts.
• Gas piping plans and isometrics for natural gas or fuel oil.
• Roof drainage plans showing how stormwater is conveyed from the roof.
• Sections, details, and schedules for the plumbing system.

Mechanical Drawings

The mechanical engineer prepares the drawings for heating, ventilation, and air-conditioning (HVAC) and other mechanical systems. Often, the numbering of these drawings begins with a “M” for mechanical. They typically include the following:

• General notes, symbols, and abbreviations for the mechanical drawings.
• Equipment layout plans showing the location of the mechanical equipment.
• Ductwork plans showing the location of the duct (supply, return, exhaust, makeup air, etc.) and its finishes (vents, diffusers, grills, etc.).
• Control diagrams showing the temperature controls and how the HVAC system is zoned.
• Piping plans for mechanical piping, such as condensate and refrigerant.
• Sections, details, and schedules for the mechanical drawings.

Electrical Drawings

The electrical engineer prepares the electrical drawings, which show the design of the electrical system. Often, the numbering of these drawings begins with an “E” for electrical. These drawings include the following:

• General notes, symbols, and abbreviations for the electrical drawings.
• Power distribution plans and riser diagrams showing how power is provided to the electrical panels, including single-line diagrams.
• Electrical panel schedules with load calculations, wiring size, and breaker sizes for each panel.
• Lighting plans showing the light fixtures and their switching and wiring.
• Power plans showing how power is provided to equipment and outlets.
• Sections, details, and schedules (equipment, conduit, wiring, etc.) for the electrical system.

Shop Drawings

The shop drawings are actually not a part of the construction drawings. The GC or their subcontractors prepare them to show how they propose to construct a building component, like a steel connection. They are submitted to the architect for review.

As-Built Drawings

The as-built drawings are also not a part of the construction drawings. The GC or their subcontractors prepare them to show where the construction differs from the design. They are submitted to the architect at the end of the project.

Tips for Reading Construction Drawings

• Check the drawing numbers against the index to ensure you have all the drawings.
• Start by scanning the drawings to get a feel for how they are organized and where things are found.
• Establish and follow a standard sequence for working through the drawings, like starting with large-scale drawings (plans) and working to small-scale drawings (details).
• Be sure to read the general sections.
• Follow the reference marks through the plans. Plans lead to building sections, building sections to wall sections, and wall sections to details.
• Cross-reference the drawings with the specifications to get a complete picture.
• Keep a list of items that need to be clarified.
• Mark off callouts, notes, details, schedules, and pages when they have been included in the estimate.
• Most importantly, pay attention to the little things.

Final Thoughts

We all know that time is money in the construction industry, and understanding where information is found on the construction drawings and how they are organized saves you that valuable time. That’s time that you can use to focus on managing a smooth construction process, growing your business, and meeting your customer’s needs.

Further Reading: Deciphering the Fine Print: A GC’s Guide to Understanding Construction Specifications