Finish Carpentry: Measuring and Marking Tips
Measuring is the key to success in every carpentry project. Measuring requires no strength or fancy tools – just common sense and concentration. Think about what you are doing and double-check your measurements. You will save time, save waste, and save yourself from doing sloppy – or even dangerous – work.
Measuring the Building
Much finish carpentry simply consists of fitting boards and panels onto the part of the structure that is already completed. To ensure that the finish work covers the framing without overlapping or leaving gaps, take the initial measurements from the framing. You may need a 50-foot or 9oo-foot tape to measure the length of a fascia board, for example. For most measurements a 16-foot steel tape should be sufficient. The hook on the end of the tape makes it possible for you to work alone.
A few situations call for more specialized tools. Measuring the inside opening of a window frame, for example, is easy if you use a folding rule with an extension slide. To measure the thickness of a board, panel, or piece of molding, a caliper is handy. Some bench rules have a caliper built into one end.
Don’t assume that walls, floors, and ceilings are square and plumb. A wall that measures 14 feet 6 inches at the baseboard may be 14 feet 6 ½inches at the ceiling. To cope with this unevenness or to correct it, use a plumb bob or a spirit level. A 24-inch carpenter’s level, which is the most versatile size, can also be used to even picture rail, chair rail, and door and window casing. When you work with smaller pieces of trim, such as balusters, use a torpedo level.
Measuring at the eaves and around stairways entails transferring angles onto your work. To determine the degrees in an angle, use a steel protractor with a swivel arm. If you simply need to transfer the angle, a sliding bevel is simple to use and will hold a setting for repeated markings.
Measuring and Laying Out Boards
Measuring the boards themselves is just as important as measuring where they will go. First, don’t assume that the boards are square. They probably were cut square at the mill, but lumber often distorts as it dries, and there will usually be checks (cracks) at the ends, which must be trimmed off. Start by cutting off one end of the first board in ½-inch increments. When there are no more checks, repeat with the other end. Then square both ends with a try square. Repeat the process for each board.
Interior finish work may require more than fresh end cuts. A damaged surface or an oversized board may have to be planed. To trim boards with accuracy, use a bench rule or a folding rule rather than a steel tape.
When you lay out cut lines on boards, always mark the angles – even if the angle is 90 degrees. All work on the job should be marked with a V to indicate a point, and a thin but dark pencil line to indicate a cut. Bisect the V with the cut line. Then cut just outside this line, remembering to allow for the saw kerf.
Right (90-degree) angles should be marked with a try square. All other angles should be calculated or transferred using either a steel protractor with a swing arm or a sliding bevel. A combination, or speed, square is good for marking 45-degree angles; a framing square can be used to mark any angle.
Marking a compound cut is a challenge. Start by determining the point that represents the farthest reach of the board. From this point mark both the side angle and the top angle. Set up the saw to follow both lines simultaneously. Experiment on scrap wood first.
Mortises, dowel holes, and other joint lines should be scribed with a marking gauge. This handy tool will also scribe accurate lines parallel to an edge for cutting strips or grooves.
