Minimum percentage in a grain bill?

[chriffle88]

When building a recipe is there a minimum % for any given grain? e.g. no point ever having less than say 5% of the bill as it will have no effect.

I guess the answer is that it depends what you are trying to achieve - my specific situation is I want to add some wheat to a recipe to help with head retention but don;t want it to mess with the flavour too much.

 

[MyQul]

As you surmise it depends on what your goals is. If for example you want to use a highly roasted malt (eg chocolate malt) just for coloring you might use 1%. (or less)
Im not sure about wheat malt but I use flaked barley for heard retention and use 5%