It's always easier to start from scratch and build a building or an addition exactly the way you want it. But economic and practical considerations often dictate that we work on the creations of others. When you remodel a building, you have to undo something that someone spent a lot of time putting together. The first challenge is to understand how the construction system was fashioned, and particularly how the loads move through that system to find their final resolution in the ground. This is essential so that, when you take the building apart or add to it, you don't upset the happy state of equilibrium that has existed for years. Three cases in point will illustrate