C#.asp.net 2010 development plan

Question

I am trying to decide the best way to develop and add some new web forms to an existing C# asp.net 2010 webform application. Basically my new webpages need to be kept separate from the other developer since his new pages are due sooner than mine are. I am basically going to have the user select my pages from the 'main' selection menu.
 
I am, thinking of using one of the following options:
 
1. I am thinking of using a version of the general webforms solution file and add my code to it in a new aspx file. This way I will use the same master pages, site navigation, and user login credentials. Thus when my code is ready, i will add the new aspx file to the general webforms solution. Is this possbile? How would i accomplish this task? Would i setup a user control?
 
2. I would create the new webforms in a solution file separate from the general webforms solution file. I would not put the 'master' pages logic into my individual web  forms. When I am finished, i will add by code to the  general webforms solution file.
 
Note: I am in a small company and we use subversion as our version control software.
 
What mehtod would you use and do you have any recommendations that I should follow? Would you accomplish this task differently? if so, would you tell me how to accomplish this task in a different manner?