hello everyone tonight

Thanks DL for the clarifier--half dovetail let in braces are a very different ball game, I can see some reasoning for their use.

One thing though I would like to discuss is that timber frame structures, including other out buildings such as barns, mills,and drive sheds to name a few, are notorious to move slightly due to winds but also other factors

saw mills, with their repetitive jerky saw carriage movements, grist mils with their grinding stones to name a couple of examples, need some freedom in their supporting framework connections so that these destructive movements will not cause fame work failure, and or wall failure

Half dovetail lap connections are noted only where rigidity is not a problem, and one place that I noted these connections used were in the attics as collar ties

I suspect that in Swiss building practices, structures relied on one another for support, and the rigid frameworks worked together as a team

separating the structures such as here in North America created a need for a new approach and I suspect someone realized houses, shops and other buildings, with their finished interiors needed a real stable fame work

I am not saying therefore that one should not use dovetail let in braces, but for me if I was approached to change a tried and proven method of bracing, I would proceed very cautiously in that regard

The above ramblings on this topic is the culmination of my experiences, It would be nice to hear from others on this topic, I am curious as to how widespread let in braces were used.

NH

Thanks Richard for your input

I also would like to hear some other chime in.

Actually the Swiss frames are extremely rigid, far more rigid than the American frames of largely English origins. There are 2 approaches to the matter of surviving stresses like unpredictable wind, sawmills, and even earthquakes. Frame design I think reflects which approach a culture chose to follow.

Some traditions designed frames to be somewhat flexible -I believe this is the thinking behind English timber framing. Other traditions designed frames to be incredibly stiff and rigid, instead of surviving stresses by elasticity, these structures survive them by distributing them through a great many members. This is the approach used by the Swiss, and I suspect is inspired by log buildings. It is often said that the timber framers among the Germanic tribes abandoned their framing styles when they came to the mountains and encountered the incredible rigidity of the log buildings there. I also think this rigid construction made its way out onto the plains and affected the development of Swiss and South German methods of timber framing (which in the late Middles Ages gave rise to the famous German Fachwerk style of framing). The log builders say that the timber frames were unsuited to the mountains, I'm not so sure this is true but either way, the log structures as built in the Alps are far more rigid than any timber frame.

I'm not quite sure I follow what you are saying about structures relying on each other, separating structures, etc. The same rules of design apply to structures both large and great, even to bridge building.

As for changing a tried and true method, I'm not suggesting that. Fact is, let in bracing is just as tried and true as mortise and tenon braces. Fact is, it's a much older method.
It actually surprised me to learn of its history in the English tradition, how in the Middle Ages it was the dominant practice and gradually fell out of use around the same time North America was being colonized. Same thing happened in Germany where dovetail braces were previously the normal method but were abandoned with the rise of Fachwerk construction -Fachwerk, you should note, achieves its bracing by setting some of the posts in at an angle, an incredibly effective solution.

When it comes to building frames in a certain tradition, by all means keep what is normal and what you are accustomed to. I am just exploring the thought process different cultures use to approach this subject.

It might surprise you to know that the large walls in these enormous buildings of frame-and-plank construction usually lack bracing completely. Carpenters discovered that the planks provided more than enough rigidity to the frame, and the braces just added an unnecessary complexity.

I'm kind of hoping Jay with his experience and knowledge of eastern bracing practices will chime in here. Figure if I call him out directly, maybe he will respond...

hello everyone tonight

I can see that you are a very deep thinker on this subject and enjoy this conversation immensely

Another angle on this thought or line of discussion is the foundations that hold up the structures, whether it be one with let in braces or those that use mortised and tendon-

I suspect that your Swiss/Germanic style buildings especially the outbuildings such as the barns sat on a permanent foundation--here in North America large flat stones were used at the bearing points, making it a necessity to allow for movement--this was the norm here in Upper Canada, also a major depth of frost to deal with, heaving could be as much as 2 to 3 inches, especially around the exterior walls

You can imagine the strain the would come to bear on very rigid let in braces situated in positions adjacent to exterior vertical wall posts, and its connecting cross tie timbers especially as it slowly raised and lowered due to frost heaving year after year- the centre posts being protected from this frost extreme would hardly show any movement, but at the same time feel the unrelenting pull and push of the opposite timber as it rose and lowered, it appears to me that failure could occur.

one final thought on this subject--the word "brace" in my opinion means just that so in any framework where there are opposing braces, and as the framework moves one of the braces is "bracing", as the movement changes direction, the opposing brace does the "bracing"--in my feeble mind a "let in brace" so to speak is not really a "brace" but rather should be named another term to address its real role in the framework

just food for thought

NH

Richard, thanks again for the thoughts

Those are some good considerations, let's examine.

The Swiss Bauernhaus, the large farm structure, does often sit on a very sturdy foundation, but it hasn't been so for very long. Old structures were set on boulders or foundations of random stone. Later on, they built more substantial foundations of mortared stone, this largely arising with the advent of cellars and more important in southern regions where the mountainous terrain requires building on heavily sloped ground.

But the biggest thing is the sill. The sills are huge and very securely joined together. They may be as much as 18" deep, and the corners are joined either with a heavy passed lap joint or with a double through wedged mortise and tenon (Don't know what we call it in English, in German it's Steckzapfen)

As for the final thought on bracing,

the word 'brace' works equally well for a member that pushes or one that pulls to prevent distortion. A steel cable, for example, braces a structure. One that pushes can be more specifically referred to as a 'Buttress' which is a member that acts by pushing the forces of one thing into another. For example, buttresses on arched structures such as Gothic Cathedral push against the walls and against the ground to redirect the spreading force of the arch. Mortise and tenon braces work similarly by buttressing the forces of one timber into another. (Though the word is more accurately used to describe an angled member that actual redistributes primary load forces, for example a strut under a balcony that buttresses the weight back into the walls of the structure)

Braces in many modern structures are designed to pull, for example in large steel framed structures we will often use long steel cables in a 'X' pattern between the posts to brace the frame. These can only act in tension.

hello everyone tonight

Well DL I do not feel comfortable working modern thought into this conversation, we all know that cables only work under tension, and were slowly adapted as the technology improved in certain instances

The early wooden bridges used wooden trusses, and cross members of wood as bracing, wrought iron rods were used as needed for additional strength, I don't really remember cables being used during that period

The 18"sills would have needed quite large trees to have remained 18" square or rectangular at 40 feet or longer, I know from experience that to square 12" at 36 feet takes quite a tree indeed,--I am guessing 4.5 to 5 feet on the butt ends or larger for those 18" timbers--just to move them around would have been a chore, unless they hewed them where they fell

NH

Your right, it does require massive trees. But they have them, in plentiful supply.

They also weren't afraid to splice the sills. This was necessary, actually, since the building might be over 100 feet in length, 50 feet wide...

And these are oak too so ya, moving would have been quite the task.

Thought you might find this interesting, here is a photo from some time ago, taken in the Emmental region at the completion of the frame of a new farmhouse. This is the modern half-timbered style that replaced older methods in the 19th century (sort of like the Swiss equivalent of stick framing in that it plowed over all of the regional framing methods, but it is still timber framing)



I thought this was an interesting picture worth sharing

Is that a flag attached to the bush atop the frame?

My recent plank walled frame is the most rigid frame I have stood upon in 20 years. No movement detected, usually I can feel things sway when someone is moving about. And, basically it only had three walls, one whole end was left open for doors, which have not been installed yet. It does have some crucky bracing, too.

I also, just today, put a porch floor down on a re do on my house. The floor consisted of 2" pine planks 12-16" wide, with a spline spanning 8' no joist. With out the spline the plank would clearly sag with my weight on it, deflect 1-1/2" in the middle, with the spline installed you would need to look carefully for the deflection, almost unnoticeable.