Installing molding and trim around doors and windows and at the top and base of the walls is called finish carpentry. The pieces must be cut accurately and fitted together so they are aligned properly without noticeable gaps.
Most do-it-yourselfers can, with time and practice, install molding so it looks good, but professional carpenters can install the same molding more quickly and with fewer mistakes. That is because they have developed tricks of the trade that make basic finish-carpentry tasks easier.
Most professionals try to avoid taking measurements. They do not measure a length, then try to transfer that measurement to the work piece, the piece to be cut to length. Instead they try, whenever possible, to hold the work piece in place and mark its length.
If, for example, the carpenter wants to fit a piece of molding over a door opening, he will hold the molding against the jamb and mark the length, thus eliminating the need for a ruler.
In situations where it may be difficult to hold the work piece in position, such as fitting a long piece within an opening, the carpenter will use a folding rule that has a sliding extension on the end. The sliding extension makes it easy to transfer inside dimensions without even having to read the scale.
Extension rules
Most finish carpenters prefer extension rules to flexible tapes for taking critical measurements because the rules remain rigid when extended. Tapes often flex and bend. This can distort the final measurements.
Most carpenters are aware that certain tools have built-in measurements, and they often use them to mark off a length. The blade of a combination square is 1 inch wide. Many framing hammers are 16 inches (the distance between wall studs) from the head to the end of the handle.
If a carpenter knows he will be using a particular dimension repeatedly in a layout, he will make his own measuring stick (sometimes called a story pole) by cutting a board to a certain measure.
Using tools with standard dimensions eliminates the need to measure and read numbers off a scale. In most cases, trim cuts for molding or doors are made at right angles so that the ends are square. This works if the frame is a perfect rectangle, but in many houses, even new ones, angles may be a little off.
If you try to trim the bottom of a door to fit into a doorway where the floor is out of level, the resulting gap between the bottom edge of the door and the floor will be uneven, even though the angles on the door are square.
This may seem like a minor flaw, but the eye picks up on divergent lines and the tapered gap at the door bottom will look like some sort of mistake.
The solution here is to trim the door so that the bottom edge is parallel to the floor. This will create an even and more pleasing gap under the door that looks right.
When fitting the last piece of molding into place, professional finish carpenters are careful not to cut it to exact length.
Instead, they cut the piece slightly long then shave it gradually with a plane, file or power miter saw to achieve the best fit.
Sometimes, however, it is difficult to achieve perfection when doing a large installation, like running molding around the perimeter of a room. The last piece may not fit exactly as planned, no matter how much it is trimmed and shaved.
Professional carpenters are aware of this problem, and they plan the installation so the last piece will be positioned in an inconspicuous corner of the room where a slight gap will go unnoticed.
An important rule in all carpentry is to complete the job. While this may sound obvious, a large number of do-it-yourselfers (and even professionals working on the molding in their own homes) run out of time, so they leave a job half-completed. Gradually, they become accustomed to a window without the casing, missing baseboard molding or a door that never gets a coat of sealer.
In addition to being eyesores that are obvious to visitors, these unfinished projects can create problems. Without the casing, cold drafts may flow through the framing around the window. The door without sealer will absorb moisture and warp.
If you cannot finish a job in the time you planned, immediately pencil in a date on the calendar when you can return and complete the work.
