Design the Architecture

• Enlist the help of a home designer to help you draw the room addition. The roofline should work well with the rest of your house. The pitch of the roof must complement the existing roof. The overhang and soffit areas must be designed to blend with what's already in place. To fit well, the addition should look as if it was part of the original house plan.
  
  

Planning the Foundation

• You will need to dig footings and create the same type of foundation for the new room that your home presently has. For example, if your home is brick with a brick foundation, you will need to brick the room's foundation to match. In planning the foundation for the new area, you will need to allow for vents and ductwork to connect to your home's heating and air system. If you decide to add a bathroom, consider routing of all plumbing as well. Plan the foundation's crawlspace to be deep enough to provide easy access for repairs on pipes or ductwork in the future.
  
  

Evaluating the Framework

• Once the foundation is constructed, you will need to have framing erected for the new room and get it under roofing. To save future money, think of adding extra insulation in the building process. One good way to do this is to build exterior walls from two-by-12 boards to allow for 12 inches of insulation. Attic insulation can be a high R-value as well. You'll need to decide whether you want to have roof trusses built onsite or ordered premade. Consult with builders to decide whether you want to cover the exterior framing with particle board or exterior-grade plywood. Each type of sheathing has its advantages.
  
  

Designing the Roofing

• Roofing for the new space should match your present roofing. It can be difficult to match the color of shingles exactly, but if you shop carefully, the difference should not be noticeable. As you plan materials and details for the roof area, remember to allow space for exterior housing for a bath venting system. Some builders merely vent steam to attic areas, but moisture problems can arise from this arrangement. Hire someone who will do a nice job of finishing up overhangs and soffit areas. These small details can make a huge difference in how any home addition turns out.
  
  

Finishing the Exterior

• As you plan your budget, don't get tempted to skimp on the quality of windows, doors or siding you will install. The exterior of your new room should harmonize expertly with the rest of your house. Otherwise, it can detract from your home's value. If your budget is tight, ask the opinion of local builders on how to incorporate part brick and part siding, for example. Or, consider buying recycled windows from another project that are high quality as opposed to installing cheap windows. By planning carefully, you will end up with an exterior you can feel proud of.