PLUS-MINUS SIGN 0.00 SPOT ELEVATION IN REVIT

If you want to assign a ± sign to a 0.00 spot elevation in Revit, here's how.
Edit the spot elevation type's properties and find the "Elevation Indicator" parameter. Here you can write for example F.F.L. (finished floor level), or whatever you want, and right beside it you type ALT+0177 as shown in this picture:

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 Now just be careful when using this new spot elevation type. If you aren't, you can make mistakes such as this one:

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For all other elevations other than 0.00 you have to go back to your initial spot elevation family. The default will read negative elevations with a (-) minus sign automatically.

Negative spot elevation displayed correctly. Click to enlarge.

Now for the third situation, when you need your positive elevations to show a (+) plus sign, go back to the type properties and apply the following variations:

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Just go to "Units Format", uncheck "use project settings" and finally check "Show + for positive values".