We try to ensure this doesn't happen, but occassionally it's unavoidable. Sometimes a client asks for extra things, sometimes unexpected issues come up that need to be worked around. For us, the key is that you are kept informed every step of the way. This allows you to make informed decisions. We also do everything in our power to keep costs down by making recommendations for how a project can be done in the smartest possible way - we call this 'value engineering'.