A caching design strategy

A caching design strategy
 
In my application I cache objects in my BLL, each BLL class has a Cachable variable that can be set to true or false.
 
In my logic I check if the class has set cachable to true and accordingly I look in the cache for the item or if it is not in the cache I fetch it from the database and add it to the cache.
 
My problem is that in the public user areas I want to always cache, this area can show "stale data" and in the priva ...