The sum function doesn’t seem to be working, it is placing the numbers next to each other. see the image below.

I have put a line between the two numbers that should be added together.

the bottom shows what the sum should look like.

Can anyone help ?

It looks like you’re pulling one of the numbers from a Revit TEXT parameter. That means that it’s actually a string object and not a number. You’ll have to convert it to a number first if you want to perform any arithmetic calculations on it:

You’re trying to add two *strings*. You’ll need to convert them to n*umbers*