While the idea of enlarging a room with an addition is an appealing thought, you should understand everything involved before you begin. Room additions are like building a new home. You need to develop a plan and a budget that includes footings, foundation, framing, walls, floor, insulation and siding, windows, doors, roof and connective lines that include plumbing, electrical and HVAC. Any renovation that changes bearing walls in a home requires a building permit. Before you go tearing into a wall to enlarge a room with an addition, visit the local building department to find out what it requires of you.
All buildings must meet the setback requirements from property lines as per local building code specifications. Some jurisdictions require a minimum setback of just a few feet from the side property line, as in Bellevue, Washington where only a 5-foot offset is needed, but it varies by jurisdiction. If your planned addition encroaches within the setback area of your property, the building department will not issue you a permit until the plans meet the requirements. Check with your local building department to find out what your setbacks are. Measure the distance from the exterior wall to the property line before you begin the planning and blueprint phase of the process to ensure that you have enough room for the addition.
Create a set of blueprints that details the construction plan. Blueprints must also contain windows, doors, electrical locations and fixtures and any plumbing. Besides these elements, include any built-in cabinetry or plumbing fixtures, as when you enlarge a bathroom or a kitchen. Unless you have experience, you will require the services of a drafter or an architect to create the blueprints. The blueprints need to meet all local building code requirements before the building department will accept your plans and issue the building permit.
To enlarge or add on to your home, obtain a building permit from the local building department before beginning construction. If you do not obtain a building permit, it creates problems later on when you go to sell the house. Without a building permit, the building department can "red tag" your house, which can define it as unsafe for human habitation. It can also force you to take down the addition if it does not meet code. The building permit ensures that you meet all building code requirements and that the construction work undergoes inspection and approval before completion and acceptance by the county.
Your local building jurisdiction defines whether your blueprints require certification or sealing through an engineer. An engineer completes the load calculations and defines the type of materials needed to enlarge your room with an addition safely according to code. Because enlarging a room with an addition usually requires going through a load-bearing wall, an engineer's review determines the best way to do that. His review ensures the safety of your project and your home when you follow his material recommendations, which include beam and support specifications.