Remember the dovetail's weakness lies in geometry: If the slope is 1 in 8, then 1/8" of shrinkage in the height of the tenon allows a whole inch of withdrawl. CB.

Man O man, geometry is every where, even in the arc of the sledge hammer used in driving the wedge. If you just place the wedge so as to make contact, home, than the above statement of 1/8" of shrinkage would be more than likely be true. Now apply some force behind the wedge and push it beyond home say 1" or until it just simply stops. Now how much withdrawl will you have? This should be calculatable, if we know how much futher the wedge is driven, this is still unknown. They very from 1"-3" beyond home. 3" is more likely due to a cutting error. I suppose one could even dry the wedge in an oven just before it is applied. Driving the wedge is different then driving a peg, there is no relish to blow out, this is when using a draw bore. These are just some thoughts bank around in my head. Tim

Yes, then you'd be counting on the compression on the top of the tenon to keep it tight, which may counteract the shrinking. Will the compressed fibers stiffen up, and lose their spring? Before the tenon is done shrinking? I don't know it that's calculable. But even if this results in a withdrawal of only 1/4", then all the bearing moves to the pegs anyway, and the dovetail stops helping. It's a cool joint, but I have my doubts about how well it works in practice. Of course there are historical examples where it worked well. I wonder if there are historical cases where it did not work so well, but no evidence was left behind :-) CB.

Is there an option for a joint on the end of dropped tie beams? The historic examples in my area show any other joint in the drop tie configuration has had to of been fixed at some time. Not all of them but most, they also far out number WHDT. Examples of fixes are the large iron staples, cables, and reenforcing nailed to the side of the tie and to the post. I have seen no repair work on WHDT, in other words they work where the simple through tenon is failing. How about in your part of the world. The only failed WHDT I have seen was the one I mentioned before. It had pulled apart I think mostly due to the structures state of being. Tim

Hi TIMBEAL,

Re reverse assembly (tie below wall plate)- this is quite an archaic form of construction and is found in a few very early and mainly aisled buildings in England (think 1100's till early 1300's) and of the examples that remain most of these are liable to be found in quite large important buildings like Great Coxwell Barn. I suppose that these buildings are of similar dimensions to the relatively large modern mid west American barns and so there might just well be a correlation between size and preferred joint design (research study ?). The dropped tie approach is much more likely to be a continental practice imported into the States by mainland European migrants. Without checking my reference books I seem to recall from correspondance with John Macfarlane that the German "Liegender stuhl truss" exhibits this type of construction and thus American practice might well be more related to a cultural design melting pot approach than evolutionary design progression.

Take care re drawing widespread conclusions on English practice from The CBA "Recording Timber Framed Buildings" book. This is a serious attempt to document joints encountered during academic study of timber framed buildings but it gives no indication as to the widespread use and practice of specific joint types. A well known Timber Frame Building book author once said to me that this book smacked of "stamp collecting" and I now know what he meant. English timber frame style and practice is not universal across the country but more specifically related to regions or even just county wide practice which might not travel very far.

Regards

Ken Hume

Ken, the U.S. is a melting pot, that is for sure. Our historic building methods alone reveals that. In my area I have a theory based on the last names of folks in this area, the Scotch/Irish, and how the area was settled starting from the early 1600's to a firm settling around the mid 1700's. I am trying to figure if there is a connection with building styles and the Scotch/Irish. I'm not sure how exactly to go about this it will take a while and a bit of poking around, mostly taking pictures and getting familiar with the local buildings.

That was the only joint of that type I found in the book. I'm not sure I made a conclusion, more like a thought in print. What is meant by "stamp collecting"? I like the book for it's simple drawings which translates into joinery options. Please elaborate with your opinion of this book. How about some suggestions on other books which could be helpfull. Thanks, Tim

Hi TIMBEAL,

Being a natural born Scot (and emmigree to Canada) I suppose that I am at liberty to reveal a few home truths about the country of my birth and its people. I am not aware of any great traditional timber building tradition being present in Scotland. That is not to say that it does not exist - more that what does exist is hidden from view behind masonry walls unlike the south of England and the continent where everything is on show. There is rude jointed cruck buildings to be found in farm settlements but a considerable number of these were raised (burnt) during the Highland clearances (in favour of sheep) when the resident population was forced to consider opting to migrate to the new world. Scotland's oldest ally is France (not England) and therefore it is not surprising that English framing traditions tend to be absent in Scotland with French design influence being dominant in many of the more important early buildings. Ireland has a similar story to tell with many of its old buildings destroyed by Cromwell and their own desperate exodus experience due to the potato famine. These countries are both windy, wet and rocky so it is no surprise that since timber does not survive well in wet external situations that masonary construction should be favoured. I doubt that very much timber building tradition translated to the new world from Ireland or Scotland but equally since both of these proud celtic nations are intelligent and highly inventive they no doubt adapted quickly to the new set of circumstances that they found in the new world. Personally, having some experience of both sides of the big pond, I have seen little in America that reminds of home grown building practice but the story in Canada is different where French, Scots and Irish styles are evident in the many masonary buildings present in that country - especially in the east.

I think that it is important to draw from personal observation and experience as well as that information contained within the pages of books and articles. Not all authors are created equal. I shall leave you to ponder about "stamp collecting".

I was recently faced with the question - "If limited to a choice of 5 (timber framing) books what would they be" ?

Answer :

1 Discovering Timber-Framed buildings by Richard Harris.

This little book can easily be purchased by those persons operating on a tight budget and having sufferred (in the biblical sense) under his marking hand on my Masters Degree essays I can vouch that he knows his stuff and rarely will he be found to be wrong or defficient in his thought processes.

2 English Historic Carpentry by Cecil Hewett.

Cecil employed his artistic skills to good and great effect in combination with his analytical skills to produce this master work. Many are critical of Cecil, quick to point out his errors here and there but this must not be allowed to detract from the value of this corpus of knowledge.

3 The Framed Houses of Massachusetts Bay (1625 - 1725) by Abbott Lowell Cummins.

This is a well researched, beautifully written and illustrated book that provides a snap shot in time that can be employed equally on both sides of the Atlantic since at that time we were the same nation.

4 Timber Frame Construction by Jack Sobon & Roger Schroeder.

Jack's knowledge, enthusiasm and understanding of his subject is hard to beat. His Garden Shed must be the most built timber frame structure in the world and it has now spawned many variants. I learned directly from Jack that sometimes it is important to see and interpret the detail in order to understand the bigger picture.

5 Building the Timber Frame House - the revival of a forgotten craft by Tedd Benson, James Gruber and Jamie Page.

This was the first timber framing book that I bought and it is notable for its inspiration and achievement in helping to set a whole industry in motion.

Regards

Ken Hume

Thanks Ken, I appreciate the input in the Scot/Irish area. Rocks, we have rocks, they probably felt right at home. I belive they moved into this area from the other parts of New England, they did not move here directly from Scotland. So they picked up building types from the south. I need more time to put some thoughts together.

I am going to the TTRAG meeting and will look those books up with Summer Beam Books. Tim

HI evryone on this thread

I do have a good slide of a half dovetail connection used in an early (1865) bridge truss. It was part of the ceiling structure of a 45 foot span framework. It shows clearly the wedge protruding on the upper surface having been driven from underneath, and only one being used.

I also contemplated if the wedge bore against a taper cut into the side of the mortise that was in line with the slope of the wedge, in my books that would have to be the case. The wedge protruded about 3 " above the surface of the 14" timber, and the shoulder of the post had raised slightly out of its original position about 1\2" due probably to its age and the steady pressure applying to the connection.
NH