In my early years of electrical, I didn’t understand the importance of cross referencing architectural prints to electrical prints.

I want to give a few examples of how to cross reference prints against each other so you can have a better understanding.

This is crucial to make the right decision the first time, trust me! (Having to redo work is the worst!)

What We Cover in This Article:

  • What is Cross Referencing Prints?
  • The Process of Cross Referencing Electrical Prints to Architectural Prints
  • Using Gridlines for Measuring Prints with a Construction Ruler (Scale Ratios)

What is Cross Referencing Prints?

Cross referencing is when you use multiple prints to get an accurate answer.

This could also involve talking with other trades and the general contractor to see if their prints line-up with yours, too!

Prints are kind of like a big treasure hunt at times!

You look at page one and it tells you to install a light in a certain spot, but then you see a little note beside it. It says to read the fine print. You go to the fine print and it says to go to page 8 to reference the ceiling height.

And then you may have to look at the architectural prints to see the ceiling type to know the depth to install your light at.

That’s a quick example of how we electricians deal with different types of prints to figure out what our engineer is wanting to accomplish.

The engineers are telling us a story, and we figure out that story over multiple pieces of paper.

And the funny part of the story is.. what it shows on a piece of paper isn’t what it’s actually like out there in the real world; that’s where things start to get fun 😉

Cross Referencing Electrical Prints to Architectural Prints

Both electrical prints and architectural prints have different jobs. Let’s do a quick little recap of what each print will tell us.

Architectural prints tell us:

  • A ceiling’s height
  • If the ceiling is drywall or t-bar
  • A wall’s thickness
  • The type of material used on the finish (is it a special drywall type, or nice wood finish on the ceiling?)
  • How things are meant to look exactly

Electrical Prints tell us:

  • Where to install equipment
  • What circuits the equipment needs
  • Often times security + fire alarm devices are on them too

And these are very important to know as an electrician:

  • We cannot have any electrical box inaccessible
  • T-Bar ceilings are our best friends (boxes are almost always accessible!)
  • Wall thickness is very important to plan for (proper mounting depth for boxes)

Alright? Let’s get into this!

Dealing with Ceiling Work as Electricians:

Let’s begin one of our examples.

In the morning we show up to work and our boss is getting us to install some lights.

These lights don’t have any circuits run to them yet, so we’re going to have to run some conduit and install some junction boxes to get these lights power!

Now before grabbing any material and instantly getting to work, let’s think ahead here.

Remember, I only like doing the job once. (Sometimes you can’t prevent this, but most of the time you can if you take 5 minutes out for pre-planning.)

Since we have to install a junction box, we already know it has to be accessible at all times. That means we can’t mount the junction box in a dry wall ceiling (unless you’re tricky and mount it right above a light you can remove.)

To check this, you go to the architectural prints. Typically if there’s a grid of squares or rectangles, you’re working with a T-bar ceiling. (These are our best friend as electricians, remember!)

This means we can run the conduit into that area and mount the junction box because we can easily pop out a tile to access the box when everything is finished.

And just something to mention when running conduit – if there is a pipe rack around, these will usually save you a lot of time. But be courteous of your fellow electricians, and don’t’ just take a space and cut off other pipes. Try to plan your route so you take your space, and don’t cut off other possible routes.

Also, before you run your pipe, you want to count how many circuits are going to be inside this pipe. We’re not just allowed to stuff a pipe 100% full until no more wires fit! You’d do this by looking at your electrical prints, and seeing which panels they all come from! (You can’t stick wires in the same pipe from different panels!)

See? If we take just 5 minutes of pre-planning, we avoided a lot of the silly mistakes.

Let’s say we’ve now run our pipe and mounted the box in the room where we are installing our lights.

We already prepared for wire-fill in our pipe and checked to see if the ceiling is t-bar or drywall.

Now we will check our electrical prints again to see the actual light type!

Don’t be that person who goes ahead and installs a light just because it fits.

When you work on a commercial job site, the lights ordered and shipped to your site have a specific place. You will look at the electrical prints and they will typically have an LD1 or LD2 for example.

You then go to where all your lights are being stored and look for this sticker.

Ba da bing, ba da boom – it’s as simple as that!

Trust me, sometimes you get 5 different types of pot lights on a job site, and 3 of them can look the exact same! But once the trims come for those lights, that’s where you can experience an oh oh moment.

I hope that makes sense!

Electrical is all about a systematic approach.

Plan, plan, plan, do the task!

Why Wall Thickness Matters as Electricians:

Electrical boxes are only allowed to have a certain amount of gap from being flush with the drywall. If your box is too deep, you’re supposed to use an insert (I started calling them oopsies on one job site lol), or you have to move the box down to be flush to meet code.

This is why knowing the wall’s thickness is very important before you start installing electrical boxes, and falls into that pre-planning stage.

On the architectural prints on every wall, it will show a certain code. We then take this code to a legend which will tell us how much drywall is going on that wall, as well as the type of drywall.

You may be thinking why does is it only allowed a certain gap from being flush with the drywall? It comes down to fire safety I believe.

You may also think, “Okay, well if the box is buried far back, I’ll just move it forward.” And the answer is, sometimes its just not as easy as that.

When a box is buried deep, it creates these hard angles to access a box for screwing into. And the biggest point is if the wall is finished (painted and good to go), you’re trying to do all this without any damage. As if you were never there!

Now get this:

In residential we typically use plastic boxes. They have tabs which we’d break off to mount the box out further.  If we make a mistake once drywall is up, it’s still possible to move the box back if need be. But in commercial we use mud rings (plaster rings), which don’t really give us much play if we screw up!

A mud ring goes on a 4x4 box which allows you to mount devices on it like a switch or plug after drywall is up. These mud rings come in different depth sizes depending on how much drywall is on the wall.

If a mud ring is too shallow, we don’t meet code as we’re only allowed a certain gap between the electrical box and the drywall.  But if the mud is too far out, it’s sitting outside of the drywall which the only solution is to switch it out!

And to fix a mistake like this with a mud ring, you typically have to do a bit of drywall damage which will require some patching!

Take the 5 minutes and look at the architectural prints before boxing to see your wall depths!

Ceiling Height is SUPER Important As Electricians:

We already talked about ceiling work, but I want to make another important point in regards to Architectural Prints and the height of the ceiling.

Ceilings height is VERY IMPORTANT to know as electricians because we must know how low we’re allowed to mount a box in the ceiling, or if we are going to mount a pipe on the wall, we don’t want to have to go back and fix this after.

If we’ve already pulled wire through that pipe, that’s just extra hours we wasted!

By looking at the architectural prints for exact ceiling height, you know if you’re safe or not. allowing you to just do the job once!

Let’s say the ceiling at 8 feet, don’t mount the pipe at 8 feet 1 inch. Play it safe and put it up a bit – this allows you to do the job once and only once!

Measuring Prints off Grid lines (Scale Ratios and Ruler)

Grid lines are crazy important for us construction workers.

Every trade uses grid lines for measurement to get as close as possible to the prints designed by engineers!

We can identify grid lines on our print typically by the letters and numbers just outside of the print’s content.

On the prints, there is a line between the same letter and same number.  So if A is on the top and bottom, a line is drawn between them, which we call a grid line.  If the number 1 is on the left and on the right, a line is drawn across them, too, forming another grid line!

This helps tremendously when finding the correct orientation of a building, where you are actually standing in a building, and where to install your equipment!

To go further, these grid lines are actually columns/footings that the building is built off of!  This is why it’s so important to use these for measurement because all trades are using them for their own measuring!

Using an Architect Ruler for Measuring Prints

If you look at an architectural ruler, it has a bunch of different ratios on it.  These can be 1:50, 1:100, or 1:125 for example!  Our print tell us what ratio to use, so be very careful to take note of that before measuring!

Let’s say we want to measure for some pot lights we will be installing in the ceiling.

We first take note of the print’s scale ratio.  We then turn our architect’s ruler and rotate it to the correct ratio.

You then start at 0 and measure your way to the center of the pot light.  Since I am in Canada, we often work with measurements in metric (centimeters and meters.)

If this pot light lands on 3 for example, that would be 3 meters from the wall, or grid line, depending on what you are measuring off of!  You would then measure in between your pot lights to know the exact measurement.  (To get really fancy, you’d set up some string, and make an awesome grid for precision!)