• Lot line and size. Check with your local building inspector's office for restrictions on how close you may build to your property line. Even if your planned addition falls within established guidelines, evaluate how much of your yard it will consume. Will you still have space for casual entertaining, gardening, children's play, or other outdoor activities? Though the addition will add value to your home, a postage-stamp lawn could undermine its resale potential.

• Terrain features. Does your property slope? Lie perfectly flat? Cross a floodplain? An addition may affect water runoff and drainage, which could result in long-term foundation problems or basement flooding if not addressed properly. Will trees or a hill block the light you crave? Note that the removal of mature trees could deprive your home of cooling shade in the summer.

• The compass. Think about the direction the room will face. If you envision a room flooded with sunlight, don't build it on the north side of your home. On the other hand, glare or heat from west-facing windows could chase you out of your beautiful new room on summer evenings.

• Impact on existing rooms. Consider how the addition will affect traffic flow and available natural light in other parts of your house. Don't forget that a high roof line on the addition could impact the view from rooms on the second floor.

• Proximity of neighboring homes. Obviously, you don't want a new picture window to look straight into your neighbor's living room. But other factors can influence where your addition goes and how large it can be. For example, an addition that blocks sunlight from reaching a neighbor's solar windows could land you in court.

• Aesthetics. Other factors permitting, you can tack an addition onto any side of your home, but do you want to? Consider how the proposed addition will affect the overall appearance of your house from multiple angles.

From the magazine, Remodeling Planning Guide