StringBuilder.Append("
") does not create a new line in the text file

I am outputting a Gridview as text file and this is part of the code
Dim str As StringBuilder = New StringBuilder()
  str.Append("<BR>")

In the output txt file,
instead of going to next line or creating a line break in the textfile when it read next row of Gridview, it adds an undesirable <BR> at the end of the line in the text file.
How can I modify this line of code ?
Thanks