Building an addition is often more like remodeling than new construction, especially where the addition meets the existing structure. Joining the new to the old — "tying in" — doubles the chances that a problem will sneak up on you. On top of all the problems of new construction, it may also be difficult or impossible to uncover crucial construction details in the existing building before work begins. Look Before You Leap The best place to solve problems is in the design, estimating, and contract- writing phases of a job, where it can be done without the use of a nail puller. For instance, in a 20 x 28 two-story addition I recently bid on, the architectural plans specified 2x12 joists