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This article describes and illustrates different types of marks found on old wood boards and beams: adze and axe marks, hand sawn lumber, mechanical pit-sawn lumber, circular saw cut marks, and modern planed or sanded smooth dimensional lumber. We include a table of modern dimensional lumber nominal and actual sizes for kiln dried and treated wood.
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Generations of types of saws used in cutting beams, and similar details are readily available on many buildings and offer both clues to building age and wonderful aesthetic detail. Below, in rough chronological order, we illustrate different types of saw and tool cut marks in wood: adze cuts, hand sawn pit saw marks, mechanically-operated pit saw marks, circular saw marks, and unmarked, planed modern dimensional lumber.
Adze cut marks in wood - hand hewn beams and planks
The saw cuts visible by flashlight on this sawn beam form an irregular "vee" shape, a clear indicator that this beam was cut by hand using a two-person pit-saw.
Our photo-left, shows a hand-sawn pit-saw cut beam or plank. Hand-sawn planks and beams are marked by straight saw kerf cut lines that include intersecting angles marking the "up" and "down" cuts made by the sawyer who stood on top of the log (the "up" cut) or beneath the log in the pit (the "down" cut).
This beam was cut before mechanical saws were available, but after hand-hewn beams or raw logs were in common use. This places the age of this structure perhaps in the mid 1700's.
Parallel pit saw cut marks in wood - machine operated pit saws
We can contrast these saw marks with the mechanical pit saw which followed, then with circular saw marks, and later with planed dimensioned modern lumber of two generations. We include illustrations of these markings and surfaces below.
Our photo (left) illustrates a wood member cut on a machine-operated mechanical pit saw. In comparing the saw cut marks on this lumber with the hand-sawn wood above, you will notice that the saw kerf marks are all vertical across the wood, all parallel, and quite regular in spacing.
Depending on the location, mechanically-operated pit saws were in use as early as 1840 (in New York), later in locations further west in North America.
Unlike the hand-cut pit saw marks in our photo above, a mechanically-operated pit saw leaves vertical saw kerf marks that are parallel as the pit saw blade was moved consistently and vertically while the log was pushed slowly through the saw machine.
Rounded circular saw cut marks in wood - modern sawmills
Now a hand saw might also leave somewhat "rounded" saw cur marks on lumber depending on how the sawyer moved his/her saw.
But hand sawn kerf marks will be irreglular in the curvature and will not be neatly parallel to one another.
The radius of the curve of the circular saw cut marks in this beam is quite large - that is, the round saw blade marks are flattened on the lumber, indicating that this was a large-diameter saw blade.
Lumber that was cut on smaller -diameter saw blades will, of course, show saw marks whose rounded radius is smaller as well.
Our photo at left illustrates circular saw blade marks that may indicate lumber from two different sawmills or at least two different circular saws, as the radius of the curved lines appears different in the lumber at left from that at right in the picture.
Keep in mind that lumber within a single building may show a variety of saw cut mark types and ages. That is because lumber may have been re-used or may have been cut at various times and at different mills but all may have been used in a single structure.
Also a old building that has been repaired, remodeled, or expanded and extended is likely to contain wood cut at different times and using different generations of equipment and sawing methods.
Dimensional lumber - machine cut and machine planed lumber
Into the 1930's, dimensional lumber (2x lumber, or 2x4's, 2x6's, 2x8's etc.) was actually cut to a size quite close to its nominal dimensions: that is, a 2x4 was close to 2" x 4" in cross section.
By 1940 dimensional lumber was cut and planed to a smaller actual size. A modern 2x4, for example, is about 1-1/2" thick by 3-1/2" wide.
Our photo (left) illustrates a modern kiln-dried 2x4 wall stud, cut and planed to a smooth-surfaced dimension of 1-1/2" x 3-1/2".
Actual dimensions of modern 2x lumber vary, and vary more widely depending on whether or not the members are kiln-dried (more likely to be exact in width) or pressure treated (still wet) or not kiln-dried SPF (Spruce Pine Fir) lumber. Modern framing lumber is provided in these dimensions:
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