How To Read Blueprints: Follow This Complete Step-By-Step Guide

They say a picture’s worth 1,000 words. If that’s true, then blueprints are worth volumes. On a construction site, in a manufacturing plant or any number of jobs that require blueprints, drawings are the vision of the project on paper, combined with as much detail as possible. To understand how the project must come together, both on a large- and small-scale, reading the drawings and plans is a must. While the process of reading and understanding blueprints is pretty simple, a lot of people struggle with reading blueprints in the beginning. Not to fear, though, because it just takes a little practice and guidance to understand them. So how do you read blueprints? Follow this step-by-step guide! Click the links below to jump ahead:

• Why Are They Called Blueprints?
• Typical Drawing Sample For Discussion
• 5 Common Types Of Drawings On A Construction Project
• Drawings In Each Phase Of A Project
• 3 Typical Views On Plan Drawings
• How Do You Read Blueprints?

Why Are They Called Blueprints?

Let’s get this one out of the way. Blueprints are no longer blue!

Construction drawings have been used for centuries, albeit much less advanced in the past. In the 1800s, a method called blueprinting was developed for creating copies of documents. One must first create a drawing on translucent paper. Separately, a chemical compound of potassium ferricyanide and ferric ammonium citrate is mixed and layered over a blank piece of paper.

The original translucent drawing is placed on top of the chemically-coated blank sheet, and a reaction occurs when exposed to bright light. All blank areas of the original drawing become blue on the new copy, while lines from the original remain whatever color the blank sheet is. This blue is known as Prussian Blue.

While drawings are all computerized now, the name “blueprint” has stuck, and now means any type of construction or detail drawing.

Typical Blueprint Drawing Sample For Discussion

Throughout this guide on how to read blueprints, we will refer to the sample construction blueprint below. This drawing shows information that is typically found on most blueprint drawings.

Now that we’ve seen a sample of what a typical blueprint looks like, let’s discuss the types of blueprints and drawings that exist, along with the purpose of each.

Types Of Blueprints & Drawings

On a large construction site, you’ll find thousands upon thousands of drawings. This because there is just so much information to account for. Between drawings that are drafted prior to construction starting, drawings that are produced when construction is underway and all of the different trades associated with each phase, working on a large construction project requires an understand of all the different drawing types you’ll encounter.

5 Types Of Drawings On A Commercial Construction Project

• Architectural – “A” – Architectural Drawings Depict The Overall Intent & Appearance Of A Structure, Along With Expected Dimensions, Orientation & Details.
• Structural – “S” – Structural Drawings Combine Architectural Drawings With The Calculations & Analysis Performed By A Professional Engineer. Structural Drawings Are Labeled With Exact Sizes, Dimensions & Requirements Of Structural Components.
• Electrical – “E” – Electrical Drawings Depict Panel Locations, Conduits, Wiring, Electrical Fixtures & Anything Else Related To Power.
• Plumbing & Sewer – “P” – Plumbing Drawings Depict Fresh Water & Sewer Lines, Tanks, Drains, Sink & Shower Locations & All Other Components Related To Plumbing & Sewer.
• Decorative ‘Finishing’ Drawings – “F” – Finishing Drawings Depict Non-Structural Decorative Work. This Includes Things Like Sheet Metal, Tile, Woodwork, Plaster, Moldings, Etc.

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Types Of Drawings By Phase Of A Project

Depending on where the project’s at in its’ life cycle, different types of drawings are required. Here are a few common blueprint drawing types:

• Design Drawings – Also Known As “Bid” Or “Concept” Drawings, Design Drawings Are Drafted For The Purpose Of Showing Intent. They’re Drawn By Design Professionals, Such As Architects & Engineers, Before The Project Is Underway. They’re Used To Illustrate The Desired End Product, And Are Also Used For Contractors & Manufacturers To Establish Costs.
• Surveys – Produced By A Licensed Surveyor, A Survey Illustrates Information Critical To The Land On Which A Structure Will Sit. This Includes Elevations (Relative To Sea Level), Property Lines, Grid Lines (More On These Later) & Other Information Pertinent To The Landscape.
• Shop Drawings – Shop Drawings Are Drawn By Or On Behalf Of Contractors Who Will Actually Build The Structure. These Drawings Are Produced With Constructibility In Mind. For The Most Part, They Take Into Account Actual Products To Be Used, Verified Field Dimensions, Final New Dimensions & The Actual Details On The Job.
• Fabrication Drawings – As One Can Imagine, These Drawings Are Produced By The Person Or Company Who Will Actually DO The Fabricating. For The Most Part, Fabrication Happens Offsite. The Items Getting Fabricated Will Become Part Of The Structure Once Fabricated & Installed. These Drawings Include Information Like Highly-Accurate Dimensions, Exact Placements, Angles, Etc.
• As-Built Drawings – Drawings That Are Created To Show Final In-Situ Conditions On The Project Once It’s Finished. Essentially, As-Built Drawings Depict Deviations That Have Occurred From The Approved Set Of Design, Shop And/Or Fabrication Drawings During The Actual Construction.

How Do You Read Blueprints?

Now the fun part. Let’s talk about how to actually read these blueprint drawings!

It’s worth mentioning that all construction drawings essentially show one of three vantage points – that is, the viewpoint of where the ‘observer’ of the drawing will be looking from. Here are the three detail types:

Plan View – Otherwise Known As ‘Bird’s Eye’ View, A Plan View Drawing Is Drawn From The Perspective Of Looking Downward From Above. See Photo Below.

Elevation View – This Viewpoint Is From Standing Next To The Structure. If You Are Standing On The Sidewalk And Looking At A House Across The Street, You’re Seeing It In Elevation View. See Photo Below.

Axonometric View – Also Known As A ‘Three-Quarter’ View, An Axonometric View Of An Object Is Essentially A 3D Depiction Of An Object On A 2D Drawing. Take Our Elevation Example From Above. Once Standing Directly Across From The Front Door Of The House, Walk To Either The Left Or Right So You’re Now 45 Degrees From The Front Door. You’ll Still See The Front Of The House, But Also The Side. This Is An Axonometric View. See Photo Below.

A General Approach To Reading Blueprints

There are a few approaches that are best to follow when reading drawings. Here are a few general approaches to reading blueprints before we go through the details:

• Think Big-To-Small. Get A Good Handle On The Biggest, Broadest, Most Overall Details First Before Diving Into The Details.
• Know That Drawings Aren’t Perfectly Coordinated. Architectural Drawings Will Show SOME Information Related To The Structure, But Not All. This Is Because Multiple Parties Are Responsible For Producing Their Own Drawings. The Plumber, For Example, Is Not Concerned With Getting Every Architectural Detail Right, Nor Are They Responsible. Look To The Appropriate Trade Set For The Most Accurate Information Related To The Scope.
• Use The Latest Version! Construction Drawings Get Updated All The Time. Refer To The “Revisions & Changes” Table On Each Drawing.
• Make Sure Drawings Are Stamped. If They Aren’t Stamped, They’re Not Legitimate For Construction, For All Intents & Purposes.
• Orient Yourself First. Look At The Drawing Title, Compass & Perspective To Properly Visualize Where The Drawing Is Seen From.
• Refer Only To Structural Drawings For Actual Component Size, Type & Assembly. Before Building Anything In Reality, ALWAYS Refer To The Drawings Put Together & Stamped By A Professional Engineer.

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How To Read Blueprints: What To Know About Written Information

Let’s take a look at the typical construction viewpoint for a residential home from earlier in this article. Please see below.

Notice how there are images drawn, but also a lot of writing. Let’s start with the written portions on the righthand column.

This is drawing A-101. The “A” labels denotes this drawing as an Architectural drawing.

The address of this new home will be 13 Paradise Lane in Great Falls, MN. The Owners of the home is the Cardanza family.

The Architect who drew these plans is listed, along with the General Contractor and Land Surveyor.

There’s also a log of revisions and changes. This notes how many times the drawing has been updated since it was originally drawn (on 9/14/18). This drawing was submitted to the Dept. of Buildings (DOB) on 10/31/18. The Architect drew in Gridlines on 11/11/18.

The most recent revision (no. 3) was drawn on 12/24/18. The Cardanzas decided that they want an attached garage, so the Architect drew this in after the original drawing was made.

This ‘revisions and changes‘ section is important, because drawings change many times after being originally drawn – working off the most recent version is essential!

You’ll find other key information on the righthand column too, such as the drawing title “Foundation Plan, Dimensions & Details – Ground Level“, the Architect’s project no., the drawing name A-101 and how many drawings are in the total set (63).

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The scale of the drawing is also listed. In this instance, 1″ on the drawing equals 10ft in reality. While this drawing is something I made for this article and not really to scale, a proper Architectural drawing can be measured with a ruler to calculate the exact dimension that the building will actually have.

Note: for this scale to be correct, the drawing must be printed full-size! A smaller version like 8.5×11″ or 11×17″ will skew the scale.

Lastly, note the empty box labeled “Architect’s Seal“. This spot is reserved for the Registered Architect to stamp the drawing. This proves that a Licensed Architect has drawn and reviewed this drawing for completeness. On Structural “S” drawings, this spot will be stamped by a Professional Engineer.

The written content on the righthand portion of blueprints contains all of the essential information related to the specific drawing that’s pertinent to the project as a whole.

How To Read Blueprints: What To Know About Drawings & Details

With the written content on the righthand side now understood, let’s review how to read the blueprint itself. Below is the same drawing again.

First off, the General Construction Notes list all of the information, assumptions and qualifications related to the drawing that the Architect feels necessary to convey. Some of this basic information includes:

• All Dimensions To Be Verified In Field (VIF)
• Refer To Structural Drawings For Final Dimensions Of Components
• Drains, Utilities & Fixture Locations Are Not Final
• Gridlines Are Drawn In Accordance With Land Survey

Next, it’s crucial to review the drawing’s Legend. The Legend summarizes what all symbols, textures and icons mean. The Legend on A-101 above notes the symbols for slab-on-grade (concrete), typ. foundation footprint, floor drain, elevation marks and sand/gravel. The Legend should be referred to whenever a symbol or icon is not expressly labeled or understood.

The compass notes the orientation of the house relative to ‘magnetic north’ – the same north that’s seen on a traditional compass.

Blueprint drawings are made up of a series of details. Detail no. 1 shows the basement floor plan. This plan view drawing shows the dimensions of the main house’s foundation and the garage’s slab-on-grade foundation. One can see that the foundation for the house measures 40ft x 47ft, while the garage measures 20ft x 25ft.

Notice the ‘G.L.’ labels – this stands for gridlines. As the ‘Revisions & Changes‘ table notes, these were added to the drawing in revision no. 2 on 11/11/18. Gridlines are used like a map – they’re meant to help the viewer locate various components relative to a known mark.

See how each line runs along an edge of the house? On the job site, these gridlines are marked using stakes in the ground. They serve as an easy reference to determine where a wall or component of the house needs to fall.

Adjacent to the garage are some brackets and a no. 3 inside a triangle. This corresponds to the ‘Revisions & Changes‘ log on the right – revision no. 3 notes that the garage was added to this drawing on 12/24/18, and the no. 3 inside the triangle outlines what was actually added.

You can also see that a floor drain will be required in the basement floor.

Construction Blueprint Drawings: Details & Section Cuts

As they say, the devil is in the details. Construction blueprint drawings are no different.

A detail is exactly what it sounds like – a portion of the drawing that provides more detail and additional information that simply can’t be seen looking from afar. Details are always close up, and drawn from a specific perspective.

Details in blueprints either give a close up perspective, a different perspective or a combination of the two.

In our A-101 drawing, you’ll notice two call outs inside detail no. 1. They’re labeled A-A and B-B, referred to as ‘call-outs‘. What is a section cut on a drawing? It’s like slicing the building or structure along the A-A call-out, picking it up, and looking in the direction that the arrows are pointing.

A section cut is similar to cutting a slice of cake. When you cut the cake, you can see all of the layers that are inside it. You can’t see them from the outside, but once it’s cut, you can see all the layers.

Section cut A-A is labeled ‘typical wall section’. This is what the foundation looks like when slicing out a section of it. The top of the foundation will sit at 3,333ft elevation – that is, elevation relative to sea level, which is given an elevation of 0ft. The bottom of the foundation will sit at an elevation of 3,325ft, meaning the foundation is 8ft tall (3,333 – 3,325). Other information shown includes the width of the foundation (12″) and the thickness of the floor slab in the basement (6″).

If the wall in this detail was drawn to-scale, it’d take up too much of the drawing. This is why there’s a horizontal zig-zag line through it. This basically says that the wall looks no different in the portions that aren’t shown, so there’s no point in drawing it to scale.

Section B-B is just like section A-A, but in the garage’s foundation, not the house’s. This notes the final top-of-slab elevation as being 3,332ft above sea level. The slab is 9″ thick, with another 9″ of gravel/sand beneath it.

In Summary

We’ve covered quite a lot in this article. If you came here wondering “How do you read blueprints?”, you now have a fundamental understand of construction drawing types, the pertinent information shown on the drawings and how to interpret what’s being shown. I truly hope this article has been helpful for you. Thanks for reading!