True, Tim. We can't prove any of this. Probably ever. Al we havve learned through the past few centuries of studying the history of these things is that just about everything we have thought about origins is wrong. That's why I'm not putting these ideas down in any published material -we can't really do any more than speculate over a lot of it. But exploring and learning new things, changing our viewpoints and perspectives is always rewarding.

The planks in that picture, here for the benefit of others, simply lodge atop the joists (these beams are called 'Unterzug' in contrast to the normal word for a joist which would be 'Deckenbalken'. They are in function closer to a summer beam, but at the same time like a joist. Hard to explain, since they are unlike anything we are familiar with here in this country)



The planks are set into grooves cut into the walls -here this is a log structure- which are the primary bearing surfaces. Other than the groove -1 1/2 or 2 inch deep- the unterzug is the only support for the floor planks. Much of their strength is derived from the fact that they are wedged tightly in place.

In the timber frame structures, we sometimes use this same flooring method. It is also common for the floor joists just to sit atop the plates and the 'deckenbalken' (as they are called in this case, different region=different terminology) rather than be set into grooves. Newer structures used more beam support and thinner floor planks, and often even just set planks into rabbets cut onto the top edge of the support beams. The floor boards remain stationary by virtue of the fact that they are splined together. Fasteners are uncommon. Nails are rare.

If lodged on top, the unterzug seem to very thin in vertical section, does it not? The ceiling is not used as a floor above? So no load other than the dead load. I was in hopes the planks set into a groove cut into the side of the unterzug.

It seem they were running low on trees and decided to use thinner logs for the side wall, they typically ran horizontally? No, the planks are substantial. Or how does the types of trees available determine how they built? Bigger trees yielded planks smaller trees gave log structure? Could soils, elevation, species and such things have an impact on building styles, to some degree.

The plank system is the floor for the story above. The grooves the planks set into are in the walls. Each room has its own floor system. The boards on the edges are cut with a taper and the middle board is cut with the opposite taper, this middle board is inserted through a hole in the wall and wedges the planks tightly together.

Yes the 'Unterzug does appear to be smaller than it should be. But keep in mind, it laps or dovetails into the wall logs at its full height.

As to the question of trees,

Swiss forests are incredibly well managed. Unlike most of Europe, these resources were never depleted -and at the same time have managed to stay surprisingly wild (you don't have the orderly groomed forests that you might see in Germany, for example) Very large trees are still to be found here, I don't know how many spruce trees I saw with diameters in excess of 3 feet and even larger, it was quite impressive really. Here are some pictures of the forest situation:











So changes in building process and the switch to half timber cannot be attributed to a shortage of large timber. It is probably more due to the typically Bernese obsession with efficiency, even where efficiency isn't important.

The types of trees is fairly universal across the canton, even from the mountains to the lowlands. The primary building material is Fir and Spruce, which is by far the most common timber. The biggest difference is what they use for sills, lowlanders use oak because they have it. In the mountains oak cannot grow, so they use larch.

But I do think the matter of space and movement affected the changes. In the lowlands it is easier to build an expansive timber frame, and you build larger structures because your operations tend to be more spread out. In the mountains, space is important. It's also a matter of weather. The lowland timber frame would have a hard time surviving mountain weather -think 15 feet -that's right, FEET, of snow. It's kind of hard to explain, but it really does just make a lot of sense to build a log structure in the rugged mountains.

I will have to put up some good pictures of these wall styles some time so it is clearer what I am referring to

OK, here we are then. Here is some frame-and-plank construction, and one example of the Half timber style. Hopefully this will help to put things in context.

Most of these are built in the platform style, number 6 is a high-posted style structure. Image number 4 is a good example of how the frame and plank wall looks on the inside. Often the interior walls are paneled and you cant see this detail.
On image 6, observe the boards projecting out of the front of the wall, Tim. These are the tapered floor boards inserted through the wall timbers to wedge the floor in place. In the timber frames, this system often was replaced with a system of simple lodged floor boards without the tapered boards projecting through to the exterior.

1
2
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6
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10

I'd be interested in comparing what you see here with some New England and other Colonial framing methods, those of you with experience in those areas.

So the unterzug is a tensions member.

In the vertical plank wall system we recently completed we put a wedged plank in the center. It can't be tightened now but we used it to tighten the planks when laying them out.

I like pic #2, others seem on the large size. Are all structures built in this manner? What are the variables, modern construction, you may have covered this already.
Here you can drive down any road and see house trailers, modular homes, owner built stuff, high end homes and old farm houses.

1 and 2 I believe are the same structure. It is what would be called a 'Stöckli' which is a small structure built for the old managers of the farm to live in after they retire. The larger structures are what you would call a 'Bauernhaus' which are large structures that house a few apartments on one end and a barn on the other, with a very large hay loft above.

Yes the Unterzug is primarily a tension member in terms of horizontal forces, but it's main function is just to sit there and hold the vertical loads of the floor

Tim, did you take any measures to account for movement in your planks? In the plank floors, the final wedged plank is left proud so that the owners came come back after a year or two and drive it back tight. The disadvantage of course is that the projecting floor board is able to work its way out since there is noting to hold its end.

The vast majority of structures are timber framed in this region, though today buildings of the half timber style are as common as the frame and plank style. Keep in mind, though, that few rural buildings are under 100 years old and most are much older. 400 year old farmhouses are not overly uncommon here...

You are right about the size, Tim. These buildings are enormous. Remember, 2 or 3 families and a dozen or two milk cows and enough horses to meet the needs of the entire farm all would have called one of these structures home.

Hello everyone again,

I've been exploring the topic of bracing and how different people view the concept. While tension bracing is known in this country, carpenters in America most certainly favor the concept of compression bracing. Swiss carpenters are the opposite; compression bracing is used at times, but the vast majority of frames use tension bracing.

We all know the basics of this, tension braces are easy to set, being added after the frame is raised, but can come out or if they shrink they will fail. Compression braces have to be set as the frame goes together and once they are in they will not be coming back out.

But there is an important dynamic I've been thinking about here that has a major reflection of joint design. That is the reactive forces that result in a frame in response to the action of a brace.

For every action there is an equal and opposite reaction. Simple Physics

A compression brace pushes against wind loads,the framing members it connects react to this force. The result is that these braces can potentially pry timbers apart, for example a girt set into a post might be pulled out of joint by the brace connecting the two. The solution to this is to make a tenon long enough so that it can be secured against this force with pegs without shearing out the tenons. Another solution is to use a 4-brace network at every such connection.

But tension bracing doesn't do this. Tension bracing acts in reverse, it is designed to pull back against wind loads. There is of course a resulting force that happens, but it is again opposite. Instead of potentially prying members apart, tension braces actaully pull joints together. This is reflected in joint design, where Bernese Carpenters effectively use very short tenons to connect structural girts to posts.

They also use this aspect of tension braces to their advantage in some cases. They might add a brace where it is not needed to act against the wind. The brace in this case is there to pull the joint together and thus secure the connection.

The big disadvantage is that tension braces have to be very stable. If they twist or shrink excessively, they will fail. The stock used for these needs to be very straight and well seasoned to prevent this. Compression braces can be made of anything -in the past they were cut of the sticks that were not good enough to use for anything else.

Nevertheless, Carpenters in the Canton of Bern certainly consider tension braces superior and continue to use them today. Not to mention the fact that in log building practices, they are the only practical choice for reasons of assembly.

hello everyone tonight

good discussion

In a way I don't see your argument for tension bracing, it seems to me that you are putting a lot of faith on the wood pins holding the braces in place, which are situated in short tenons, with straight grained wood, these could easily fail

Compression braces due to their position and roll would have to actually be crushed in order for the building to collapse, and in all my examinations of old frames never have I seen any crushed, no matter how old

The only thing that I can say as a positive for pinning a brace is to hold it in position should the frame become very loose over time, thereby allowing it to remain for a compression thrust during a weather crisis like a tornado passing through the area

Could you explain how one would create enough relish on the end of a brace to enable a wood pin to do this heavy duty job assigned to it

interested

NH

Sorry I should clarify...

Tension braces discussed rely on a half dovetail joint, the let-in type. The dovetail pulls against the wood of the posts and beams. Not talking about mortise and tenon joints for these.
The only function of a peg in these dovetail joints is to hold the braces (which might only be 2 inches thick) in the joint pocket.