How to Read Construction Plans

January 7, 2021

Before you put together a bid on a construction project, you’ve got to know the scope and the amount of work that’s involved. Information about the work to be performed is provided through construction drawings (plans) and specifications. Contractors use these documents to quantify the work and estimate what it will cost to complete the project.

When you first look at a set of construction plans, they may look a little foreign. There’re so many symbols, abbreviations, and both large and small drawings. It’s hard to tell what they are trying to represent. Knowing how to read construction plans is a skill that construction professionals must acquire and continue to develop as they go through their career.

So, here are some tips on how to read plans before putting together a bid.

What are construction plans?

Construction plans are drawings that provide visual instructions for contractors about what to build and how to build it. They offer both a general representation of the project as well as detailed illustrations of specific installations. They represent the entire scope of the project and include all disciplines and scopes of work needed to complete the project.

How are plans used in the construction bidding process?

Plans communicate the architect’s and engineer’s design intent so the owner can visualize their completed project and everyone on the job is working from the same instructions. In the bidding process, plans are distributed to contractors to bid on the work outlined.

Contractors and subcontractors use plans to determine the scope of work and whether they want to bid on a particular project. Once a decision has been made regarding bidding on a project, estimators use the plans to quantify the work and provide pricing. If they have questions regarding the plans during the bidding process, they can submit their concerns to the design team for a response.

Answers to questions, and even revised plans, are often issued during the bidding process. Contractors should expect these kinds of changes up until bid day.

Plan components

Cover page - The cover page gives comprehensive project information, including the project address, code requirements, a map of the area, a site plan showing the area of work, a list of project team members, a list of drawings, and the symbol legend.

Set - A group of plans for a specific project is called a set of plans.

Sheet number - Sheet numbers identify individual sheets or drawings. They often include a leading letter that specifies the discipline or scope of work (A-architectural, S-structural, C-civil, M-mechanical, E-electrical, P-plumbing, L-landscaping). Unfortunately, there’s no consistent system for numbering sheets, as each architect or engineer often has its own.

Scale - The scale is used to determine dimensions on a plan if they aren’t given explicitly. It shows how many linear feet or meters are represented by a unit of measure on the drawing. Each drawing, or even each drawing component, may have a different scale in a set of plans.

Schedules - Schedules provide a list of materials or equipment that are needed for the project. They often offer detail on the type of material, manufacturer, size, or other characteristics. More detailed information about materials can often be found in the specifications.

Elevations - Elevations are cross-sections of the surface of a wall or room. They are usually used to show finish materials and placement.

Sections - Sections are cross-sections of the interior of a wall or room. They are usually used to show interior construction of walls or a roof.

Details - Details are maximized drawings that show the details of the construction in a small area. They are represented by a circle divided in half, with the detail number on top and the sheet number on the bottom. A symbol is placed near the area the detail is representing, and then again on the sheet, the detail is shown on.

Tips for subcontractors on how to read a set of plans

1. Review the first few pages of a set of drawings to get the general project information. Pay special attention to any notes.

2. Look at the cover page and drawing index to find the drawings for your scope of work and note the sheet numbers.

3. When reviewing the sheets for your scope of work, read the notes on each one to get details of the work you’ll be performing.

4. Take note of any materials included in schedules, like the finish schedule or door schedule, in your scope of work. For more detailed information, review the specifications.

5. Use a scale ruler, electronic scale, or take-off software to determine the amounts and quantities for your work. Always double check measurements for accuracy.

6. Always review the specifications for your scope of work for detailed information on materials and execution procedures.

7. Reference the drawings for other scopes of work and review them to coordinate and verify locations and measurements.

8. If something isn’t clear or there’s a conflict in the plans, submit a question to the general contractor using an RFI.

Reading plans takes practice

Design teams use construction plans to communicate a building’s design to contractor teams. They include drawings of the overall structure or project, as well as more detailed drawings showing a specific area of the building or even a particular building assembly. Contractors then use those drawings in their construction bidding process, as they help them understand the work involved to develop a price.

While not all plans are the same, many conventions are used on most of them that make reading easier. If you’re reviewing a set of plans and come across something you don’t understand, and you can’t find information on the symbol legend, then it’s best to ask someone. Guessing what the plans are trying to say can lead to mistakes in your bid or problems on the job site.

As you get more practice reading different plans, it will become second nature. Just take it slow at first, ask questions, and you’ll be a master plan reader in no time.