• Installing an exterior door is a simple do-it-yourself project if you follow the procedure. carefully and thoroughly.Door image by Mimis nena from Fotolia.com
  
  Install a new exterior door for a serious home update, both aesthetic and practical. Most likely, you'll be buying and installing a pre-hung door. Unless you've fashioned your own door, most doors you can buy will already be hung from a matching door frame. Installing the doors simply consists of cutting a rough opening and fitting the door and frame inside. Pay attention to details, and work carefully for a plumb and level fit.
  
  

Level and Plumb

• In order for your pre-hung door to open, close and swing properly, you'll need to ensure that it's square: both level, horizontally, and plumb, vertically. Use shims to make the new door frame fit snugly and evenly within the rough opening. Place a shim above the top edge of the door frame, lodging the whole frame into place. Next, add shims to either side of the door frame, both at the hinge-side and strike-side jambs. As you work, continuously use a good, long carpenter's level to keep things square. While a higher hinge-side will not cause problems, having a slightly higher strike-side will interfere with the door's closing. If you're building in an older home with irregular angles, keep the door square with regard to the level. This will keep gravity from disrupting the door's free-swinging movement. When working with shims, always use them in pairs, each one facing the opposite direction, to create level surfaces.
  
  

Sealing

• Once the door frame is squarely in place, take precautions to create a tight seal around its edges. For an exterior door, this step can dramatically affect your home's energy efficiency. Expanding foam caulking works well to seal any gaps between the rough opening and the door's threshold. If using a wooden frame, use the foam conservatively; otherwise, the force of the expanding foam can easily shift the frame out of alignment. To seal the door's bottom edge, apply a 1/4-inch line of caulking before putting the frame in place. For many climates, you may also wish to add weather stripping. Once the door is in place, replace the weather stripping regularly, checking for breaks in the seal at least annually.
  
  

Switching Door Types

• You may decide to change from one kind of door to another, such as a single door to double doors, or a solid wood door to an aluminum one with windows. If doing so, consider consulting with a professional before beginning the installation yourself. Replacing the door with a larger one will require more extensive remodeling. Before starting this project, ensure that expanding the opening won't disturb any weight-bearing elements. Likewise, if you plan to install sidelights, you'll need to make room for more extensive new framing. Should you switch from one material to another, research their respective energy efficiencies and consider the long-term heating or cooling costs.