Merge .net web app and wcf solutions

I have two solutions; a web app and a WCF 4 service. They use the same folders, databases and tables (but, obviously, different filenames).

I can publish one (the app or service) and have it run fine while breaking the other. This used to work.

My question:

Should I try to add the existing service files to the app project and publish them together or is there another/better way to accomplish this?

Thanks!