A little bit about bracing...

It has come to my attention that I should deal with the matter of rigidity of frameworks. The American frame is a very flexible assembly. It can move a great deal without any danger to the structure. Unfortunately modern codes require us to stiffen our frames somehow when we build them.

The Germans, on the other hand, build frames to be immovably rigid. They are built so that they just will not be swayed.

This simple fact is very likely a big reason for the drastic difference between the bracing techniques in American and German framing. Knee braces are all but unheard of in later German framing, instead they rely on very long braces. This is because they are expecting their braces to do two things, resist racking and resist lateral force. A short knee brace does an excellent job of resisting racking, but a terrible job of resisting lateral forces.

Since they are expected to bear 2 forces simultaneously these braces must be treated a lot differently. They have the potential to have a lot more force transferred through them than a knee brace typically will have, and for this reason it is considered bad practice to brace them against a post without an opposing brace on the same post (never on a corner post) The forces during a storm could potentially push the post out of its joint.

The reigeln also help a great deal in this regard. They by themselves don't do anything to prevent racking of the frame -dividing a rectangle into two rectangles doesn't make it any less likely to change its angles- but they do greatly limit the flexibility of the frame. The assembly makes it so that all of the posts are pushing against each other, almost eliminating the possibility of any timbers flexing under lateral loads.

When you add to this the long braces which cross the reigeln and bring them into bracing action, the frame has very little ability to rack or flex much at all.

The is 1 potential weakness with the German frame. A very long wall with no supports in this system is unstable, and the building has the potential to flex in the middle which is certainly not good, particularly with a masonry infill.

There are 2 commonly used solutions to this. The first is to brace the walls against each other and against flexing with an interior wall built in the same fashion as the exterior walls, perhaps a little thinner. The second is to use a series of framed buttresses, usually on the inside. Essentially these are wall frames about the length of 1 or 2 cavities, complete with braces and riegeln. The first is the most common, and can be easily incorporated into the floor plan of the building. The second is used if there are no walls close to where bracing is needed, such as in a large hall.