Timber framing methods

[General Strike]

My in-laws live in a German fachwerk timber framed house, built in the Viking long-hall style of Lower Saxony, and I'm quite familiar with the multiplicity of styles found around Germany. Many other countries have similar timber framed buildings, with a lot of variety of forms but constructed using very similar techniques - and until recently, every traditional timber framed building I had seen was build using mortice and tenon joints - that is, a tongue in one beam fitting into a slot in another, pulled together by a peg driven through slightly off-set holes.

However, I recently stayed in an alpine chalet in France, and although the structure was very similar to other timber-framed buildings, it was constructed almost entirely using a kind of pegged halving dovetail joint - that is, a wedge-shape was cut into the end of each horizontal, and a corresponding notch cut in the side of the verticals - a peg then went squarely through the middle of each joint. This meant that each horizontal beam didn't sit in the middle of each vertical, but was instead offset to the side. However, it got me thinking.

Firstly I couldn't see why this joint was favoured over the mortice and tenon joint I usually see. Was it perhaps because the construction was of softwood rather than hardwood? Secondly, it made me wonder why the mortice and tenon joint is usually favoured - perhaps because it's easier to work with green wood when using hardwoods, and a mortice and tenon joint would tolerate movement and shrinkage?

 

[Fraxinus]

In timber framed buildings various types of joints are used depending on the timber used and the load it has to bear or position of the joint.
In green oak buildings the draw bore pegged mortice and tenon joint is most common as it will stay solid as the timber dries and shrinks, often the slightly tapered pegs have to be given a final whack home a year after construction. Green oak is less wearing on the tools and easier to cut than old dry oak that gets like steel.
I would think that the pine was dry for the chalet build so a dovetail could be used as it would not be affected by shrinkage and become loose. The carpenter may well have thought it would look nicer too.
Another reason for using a dovetailed joint is that it is very strong in resisting directional force, hence the use of them in drawer construction as an example. Without seeing a pic of the actual use of the joint I can not say for certain as to why it was employed.

Rob.

 

[mrcharly]

I'm speculating, but the dovetail you describe would be easier for a small team to erect without much gear. They could put up the uprights, saw in the joints then lift and place each horizontal, one at a time. I've helped build barns like this and done whole sections by myself. Once the uprights are up, if a beam can be lifted by one or two people the job is easy and doesn't require much gear, just a rope to pull up a beam.

With a mortice and tenon, each panel has to made and then 'tipped up' - that needs much bigger lifting gear.

 

[milius2]

As mentioned, I think it's a lot easier to erect a building using dovetail joinery when you can put a piece up one at a time. I've build simple structures myself with my grandad an that was all the power needed.