The rings of a tree trunk correspond to years of growth. Some years are better than others meaning the amount of growth varies from year to year. The pattern of growth is typical for a region and once the standard of a regional growth pattern is established, the years in which trees start to grow (centre ring) and are cut down (outer ring at the bark) can be determined. This method of dating is dendrochronology.
Quite a few timbers were rotten and were replaced. Sufficiently sound cross sections of the removed timbers were identified and 1.5" sections made. These were sent to the Cornell Tree Ring Laboratory as part of their Northeast North America sample collection program.
I later also sent sections of the bottoms of the door frame to the basement that were embedded in the foundation wall. Note also that I sent sections of the east, west and north sill plates of the addition. The east and west plates were not squared.
Figure 1. Timbers sampled from Ham House
The frame was mainly constructed from white pine while most of the sill plates and ground floor timbers were white oak. The basement door frame was white cedar.
Figure 2. Dendrochronology Results
Only an oak ground floor beam (timber-A1) had bark on (B). In addition one of the oak sill plates (timber-B) and the white cedar door frame had a waney edge (W) suggesting the outer ring. All three of these timbers were felled in the winter of 1816/1817. The remaining timbers were consistent with this fell date. "v" indicates close to bark and "v v" indicates an unknown number of rings removed.
One of the most remarkable results was the year the NW sill plate (timber D, white oak squared to 8"x10") started growing - 1498! This was the oldest historic timber from eastern North America yet seen by the Cornell Lab.
The east and west sill plates of the addition were both felled in 1805 with the other sill plate being squared, but possibly felled around 1818. The timbers of the addition had clearly been reconfigured from their original construction. It seems it was originally an out building of John Davy and was reconfigured as a summer kitchen some time after the construction of Ham House.