Dendrochronology

[Tom King]

Dating a structure by taking core samples from timbers that have some of the bark edge left from the tree they were hewed out of, and comparing the ring sizes to others in the database of known dates.

Today, Mick Worthington came to an old house I've worked on, on and off, over the past 7 years.  The told history never made a lot of sense to me, and as I got into working on the house, there were things about it that made it look a lot older, to me, than the told history.  The only way to prove when the house was built was by Dendrochronology.  There are several possibilities for interesting, and important history, for the most likely dates that this house was built.  Anyway, this is about the dendro process, and not about that history.

Mick has done this for a living since the mid '90's.  It was required in the UK before any work could be done on old houses, which most over there are.  After spending 15 billion dollars hosting the Olympics, some things had to be cut.  Long story short, Mick came to the New World to work.  Today he was pulling cores for the Foundation that this house belongs to, at my request.

The two main rooms in this house had the plaster taken out, the ceilings dropped, and sheetrock put up, by the family that lived in it up into the 1970's.  We pulled all that new junk out this past Fall, and it exposed prime candidates from which to pull the Dendro cores.

The drill bits are very specialized.  For these particular ones, that leave the least damage to the timber, the cutter is only about 5/8" long on the business end, and open in the middle, to leave the core.  There are several different lengths, so you don't just use the longest one for the whole core because it is possible to bend them.  The tubular shaft is not very thick, so regardless of how fancy the steel is in it, it's still possible to bend one, and they're not cheap.

It takes a lot longer to drill one core than you might think.  Mick pushes the cutter in until the cutter end fills, then has to withdraw it, clean the end with a small brass welding brush, and take another 1/2" cut, repeating over, and over, until after switching to the longer bit when the shorter ones go to their max depth, he has drilled all the way through the timber.  The bit is pulled back out, with the core in it, and the core is very carefully pushed out with a dowel.  He then marks on it which framing member it came out of by counting joists from the end, or whatever type of framing member it is relative to where it is in the structure.

Big Mike and I helped him move his stuff around, and using one of my plastering stages, he was surprised that he was able to pull ten cores in about 6 hours.   He's not used to having help, and mostly works off of ladders.   Most of his time spent on these jobs is at the microscope measuring the core rings, and most of the time a computer finds the match once the data is all entered.

He had done many buildings, with such interesting ones when he was in the UK as the Tower of London, and several of the Royal Palaces.

I think the pictures will make it a little clearer.   We finished the day up in the attic, which was probably 130 degrees, and when we came down in the house, it felt like the AC was on even though the house has no electricity, and it was probably really 88 degrees in there.

Some friends of ours that bought one of my lake houses over 25 years ago weren't using their house, so Mitch and his Archaeologist Wife are staying in that, and have been eating with Pam and I.   We've had a great time, and they're staying an extra day, just to enjoy the lake tomorrow. 

This is either going to turn out to be a major historic find, or I'll look like a chump for convincing the Foundation to spend this 2,500 dollars.  More later on that, after we know for sure.

I haven't told this story yet, even to the Foundation Board, but thought you guys would appreciate it.

[Just Bob]

Thanks, that is really interesting to me, I appreciate your explination.

[Steve B Anderson]

That’s awesome Tom. Maybe in the near future someone will come up with a “Dendrochronologymeter” with pins similar to a moisture meter that can date the timber on site. With the advancements in technology today it may not be a question if,but when.

[Pondhockey]

Fascinating!!

Thanks, Tom.

It does remind me of a story about a grad student in dendrochronology (I can't even type that fast, never mind say it).  He broke his bit in a bristlecone pine, was ok'd by the forest supervisor to "just cut it down - we have lots of older trees", and wound up cutting down the oldest known tree in the world.  The reputation supposedly haunted him for his career.

[PS I like the portable, adjustable scaffold/platform.]

Edited June 29, 2018 by Pondhockey

[Tom King]

I use those platforms when I'm plastering a ceiling.  They're made to be the right height for working in a specific room.  We make them to take up a little over half the space in the room to be plastered.   That one Mick is on is one of the short ones we had at another old house, made to take up the end space beyond the long platforms.   Rather than changing the legs-just screwed together, we just scabbed on some scraps to raise this one to the right height for Mick to work in these rooms.  The others that go with it are 8' long.  If we used that one in another room, with different ceiling height, we would change the legs so they can all be jambed up together, with nothing to trip over while looking up spreading plaster.

The one I'm on in this picture were made the right height, and took up the full width of this hallway.   None of the commercial scaffolding ever works out to be exactly the right height, or width, and in the middle of putting up plaster, I don't want to stop and wait for scaffolding to be moved.

[Tpt life]

Saw this in a nat’l park today and thought of this thread. 

[Tom King]

This is an interesting read on the subject:

http://www.history.org/foundation/journal/spring02/dendro.cfm

[Mark J]

That was a great story, Tom.  Thanks for taking the time to write it.

[Tom King]

As is often the case, this house turned out to be a different age than the told story.   It was built in 1796, rather than the told history of 1780.   Long story, but I knew it was no way the owner built it when he was a young man, and especially during the Revolution.  It all makes a lot more sense now.