There are a lot of options when it comes to selecting a new entrance door for your home. The most popular materials are steel, fiberglass, and of course, wood. There are single doors, double doors and doors with single or double sidelights and transoms (windows above the doors). Doors can incorporate opaque panels, clear glass panes, and a variety of frosted and/or textured glass panes. And, you can select from a multitude of door designs based on Craftsman, Shaker, Mission and Contemporary styles.
Steel doors, which obviously won't warp or twist, and are unaffected by mildew or moisture (when properly finished), have a middle insulating layer (typically a polystyrene core ) that offers a better R-value than composite or wood doors. The R-value shouldn't be a major determining factor in selecting a door, as the square footage of a door represents a small proportion of the total surface area of a house. Steel doors typically come in a smooth finish and are factory primed. If you don't have access to spray equipment, or don't enjoy finishing, I highly recommend purchasing a pre-finished door. Some manufacturers and some retailers offer pre-finished doors. Choose a steel door if low maintenance, high durability, and optimal security and protection are key factors. Typical warranties are for 10 years. The main drawback of a steel door is that it can be fairly easily dented, and it can be very difficult, if not impossible, to repair the dents.
Fiberglass doors have similar characteristics to steel doors; they are dimensionally stable and come in a wide range of styles and colours. A polyurethane foam core gives high R-values, and the doors come with a smooth surface or a realistic wood grain surface that is more resistant to denting than steel doors. As with steel doors they come factory primed and have to be stained or painted before installation. Standard fiberglass doors are warranted for five years, premium doors for up to 25 years. Choose a fiberglass door for extreme climates and high traffic entrances, or if you want a faux wood look.
For a truly custom look that lends an air of uniqueness, and offers a warm, rich appearance, look to a wood door. There are two options: have a custom door shop build a door for you, or, build it yourself. Building a door is not overly complicated; however it does require that you are comfortable working with mortise and tenon joinery, have a good sized workspace, and a high level of precision in your woodworking. It's definitely not a project for the novice woodworker.
Solid Wood Doors
Some of the more popular woods for doors are Honduran mahogany, white oak, Douglas fir, eastern maple, and cherry. Regardless of the wood you select, choose kiln-dried straight grained stock free of knots or other defects. Quarter-sawn lumber is a good choice. You'll need 8/4 (2") or 10/4 (2 1/2") stock in 8" lengths for the stiles and 3' to 4' lengths for the rails. It's a good idea to mill the lumber slightly oversize, sticker it and set it aside for a week or so to acclimatize it to the humidity level in your shop.
As with many large scale projects it's a good idea to draw the plan for your door to scale. I use a scale of 1:4, and draw out each of the major joints full size.
There are a number of ways to build a door, but the easiest is using mortise and tenon joinery with a solid wood floating panel. Solid wood doors weight quite a bit, and you want to use joints that won't come apart over time. You could use loose tenons, wedged tenons, or draw pegs on the M&T joints. Ensure you use waterproof glue or epoxy on all the joints. An expansion gasket will allow normal expansion and contraction, and eliminate moisture leakage while keeping the panel centered.
If you have access to a shaper, or a router table equipped with a 3 1/4 HP router, then you can use a raised panel bit to shape the panel and a profile bit set to shape the stiles and rails. An alternative is to apply raised molding on the stiles and rails to hold the panel or insulated glass insert in place.
Before you begin building a door, purchase the hardware. You'll need an entrance set, three hinges and chrome or nickel plated screws. For doors 1 3/8" thick and 32" wide use 3 1/2" hinges, for doors 1 7/8" thick and 37" wide use 5" hinges. For intermediate sized doors use a 4" or 4 1/2" hinge. Typically, hinges are placed 7" from the top of the door, and 11" from the bottom, with the middle hinge centered between the two. If you're replacing an existing door you'll want to use the same hinge placements on the new door. Use a durable, easy to maintain finish on the door. An enamel paint is an ideal finish, but completely obliterates the look of a wood door. Oil-based varnish and spar varnish are two commonly used finishes, as are penetrating finishes like Cetol and Penofin. If the door is exposed to the elements and receives a lot of direct sunlight, expect to refinish the door every three or four years, sooner under extreme conditions. If the door is protected by an overhang or by a storm or screen door, you may only need to refinish every five to seven years.