The last argument in itoa is the radix of the outputted number. Using 10 will give you a decimal number (the 'normal' kind). 2, like you've typed, will give you a binary number (1010101110101) which may not be what you expect...
Also, remember that strings contain a NULL terminator so if you have 2 characters i it, it must be 3 characters wide.
Oh, and the easiest way would be to add the integers first, then transform them into a string. Integer addition is a lot easier to perform than string concatenation.
Assuming they are max 2 digits long each.
int Total = (feet * 10000) + (inch * 100) + six
itoa(Total, Buffer, 10);