There are many differences between woodworking in today’s machine age and the 19th century. Contemporary carpenters and furniture makers rely on drawings, dimensions, and precise measurements to help them plan and build things. Before the Industrial Revolution, however, things were very different. Although 19th century house joiners did rely on pattern books, these books didn’t contain measured plans with precise dimensions for Federal or Greek Revival doors, windows and molding. Instead, these pattern books had drawings of various elements with proportions.
What do I mean by this? Lets look at a 1797 plan book by Asher Benjamin and see. If you wanted to build an interior door today you would buy a set of measured drawings for a 2/8, 2/10 or 3/0 door which would give you the standardized width of the stiles, bottom, top and lock rails, etc. If you look at the plate from Benjamin’s 18th century plan book, you will see that the drawing is much simpler.
The first thing to notice is the series of 9 marks beneath each door. Rather than dimensions, Benjamin instructs the house joiner to divide the width of the door opening into 9 equal parts or steps with a pair of dividers. If you are building a 3/0 door, which is 36 inches in width (as in the example Benjamin gives here), you would have 9 parts or steps of 4 inches each. On this 4-panel door each stile, muntin and top rail is one part or step wide (or 4 inches), the bottom rail is 1 1/2 steps wide (6 inches) and the lock rail is 2 1/2 steps wide (10 inches).
The genius of this approach is its simplicity and flexibility. If your door opening is an odd size like 2/9, 2/11 or 3/2 (as is common on older homes), you simply step off 9 parts on the door opening’s width with a pair of dividers and record them on a piece of wood called a story stick. You then have your measurements for the entire door and can use the story stick to lay out the different parts. Regardless of how wide or narrow the door, the proportions of each component in relation to the entire door are exactly the same. This preserves the proportional harmony without having to do a bunch of arithmetic.
What’s better yet is you don’t even need a ruler or to know the dimensions of the opening. You simply mark the width of the opening on a scrap piece of wood or story stick, use your dividers to divide it into 9 parts and start laying out your door. The idea of not knowing or caring about the dimension of a door is counter intuitive for modern tradesmen, but in the 18th and 19th century this was standard procedure.
Why is this important? These differences in approach explain why modern replacement doors often look so odd in older homes. In an age when everything is standardized (e.g. the width of door stiles and rails), when a modern shop builds odd-sized doors for older homes the proportions of the door parts are usually off. They just don’t know the proper proportions governing the dimensions of the door’s various parts in older building. As a result, they don’t adjust their designs and the doors won’t match the originals.
Whenever I visit an historic home I take careful measurements of doors, windows, molding and other millwork and determine the proportions of each piece. Then, if I make a hand-made door for a Greek Revival home, I can check the measurements and proportions for doors in similar homes and use them to make the replacement. Not only does my replacement door have appropriate tool marks and construction for the 19th century, its proportions, molding and shape are also correct.