When creating a grading plan, a typical production plan shows a "pavement" and "top of curb" location in the exact same spot. Obviously, if you show the label at the same spot the "pavement" (P) and "top of curb" (TC) will show the same elevation. The best way to avoid this is to label the pavement elevation and add an offset expression to modify the text output of the TC.
Take a look at the label below:
Image 1
Notice in the image above the P and TC are offset by 0.5', the depth of the curb height. To do this, I ensured I was consistent in labeling the pavement and not the curb (if you happened to add offset feature lines) from the surface model (I have presumed you already have your surface modeled).
Go to the "Settings" tab off of Toolspace. Expand Surface, then expand Label Styles. There, you'll see Spot Elevation. For reference, see the image below. Notice there are already several Spot Elevation label types created. The ones with the yellow triangles signify that they are still be utilized. The reason multiple label styles are created is obviously to accommodate the different type of curbs/gutters and combinations.
Image 2
I am going to explain the Label in use named "TC and P" shown on the Settings tab above.
Notice above the highlighted Expressions text. This is where you create a mathematical relation between the two elevations (notice the calculator icon :) )
Right click on Expressions and the following dialogue box will open:
Image 3
Fill out the dialogue box as required. For a 0.5' high curb I filled it out as shown below:
Image 4
Let me provide a brief explanation as to what is going on above. First click on the button next to the "function- F(x)" button. You shouldn't have as many options as shown above, but you should be able to select Surface Elevation. Add the term Surface Elevation to the expression, and it will be added with the brackets shown above. Subsequently, I added 0.5' to come up that distance from the pavement. Finally, I subtracted 4000'. This was done so the elevations were only read to the tens value, for example TC=40.57 rather than TC=4040.57. You can imagine how messy the labels would read if we actually had to show the actual elevation. A note on the plan is added to ensure that the 4000' additional feet is presumed. If it wasn't, I would suspect a new contractor would be in order. (NOTE!: In the image above I am editing an expression rather than creating one. When you're first creating one, you'll be prompted for a Name as shown in Image 3. I used "imperial tc")
OK. Now, we've created the Expression. Next step is to include it in the label.
Create a Style name for your new Spot Elevation style. For this style I used "TC and P".
Image 5
Once you have the style created. Go to the Layout tab.
Image 6
Surely, you may have to make some adjustments to aesthetic style, but I'm only going to go into detail of how to apply the Expression. Under "Component Name:" Select Surface Elevation. The Expression is applied on the Contents dialogue box under Text. Notice above it shown as a long string of text that includes "{\fArial....". This will be easier to understand when you open the dialogue box.
Image 7
The dialogue box is present above. Notice now you should have the expression you created available. As I mentioned earlier, I had named my expression "imperial tc". On the right side a preview shows underlined text of "TC=" with the expression appended to the text value (all underlined). In this step, you have to select the correct Expression with the correct output format and click on the "right-arrow" to register the value to the contents.
All the work you have done so far was to create only the TC value. Now you have to create the P value. Once you create the P value, you may find that you will have to alter some of the values/variables in Image 6.
To add the pavement elevation you have to create another component (see below).
Image 8
You can name the new component "Pavement" if you like. I accepted the default "Text.1" for the time being. Now, for the new component open the Contents dialogue box.
Image 9
You'll notice above that I am selecting an expression named "two digits". This was an expression I created earlier that would truncate the 4000 additional from the label, similar to what was done in Image 4 (with the exception of adding the 0.5'). Now you have your main "P" and "TC" labels created in the style. As I mentioned earlier, you'll have to adjust some anchor points, offsets and variables for the label to show correctly, but this should show you how to get started with applying Expression in Civil 3D.
Don't forget to worked on you Dragged State settings!!!! You love Civil 3D, don't you??!!!