Monday, March 15, 2010

Following Mazerolle: "Théorie Des Devers De Pas"

Here we are at the starting gate of the process I have set for myself of drawing a significant number of the examples shown in the 19th century carpentry text in traditional French timber work by Louis Mazerolle.

The first drawing I chose to tackle is close to the beginning of the book, and is called "Théorie Des Devers De Pas", which I translate, taking some liberty, as the Theory of the Diverse Feet. While the word devers, means 'inclination/slope', I am choosing to use the word 'diverse' instead as I think it gives the meaning a little better.

You see, drawing the footprints, that is the outlines of a stick where it meets the floor, is a core technique in French layout. Imagine a square piece of timber with a square cut on its end - if you were to ink or paint the end, and then place it upright upon the floor for a moment, the mark left behind on the floor would be an exact outline of the stick itself. If that same square stick were cut with a slope on one end, and the same procedure were followed, then the footprint left behind would be a rectangle, the more acute the cut angle, the longer the rectangle. If the piece inclines in a compound manner, i.e., in two directions at once, or the stick is not a square section, but irregular or polygonal, and is one slope, determining the footprint shape becomes a bit more difficult. The théorie presents a method for determining the footprint of any stick of wood at any slope and rotational position.

Why figure out the footprint? Well, once the footprint is established, it is then 'easy' to determine the alignment of any face of the piece in relation to the plan, to mark intersections of the piece with the plan so that these marks can be easily transferred along the piece in question, and so forth. It's an interesting method. Here's how it devolves:

At the top of the drawing you can see the common rafters drawn, an elevation view. The plan, A~B~C~D, is an irregular quadrangle. The common rafter pair would be situated on the plan such that their feet would be placed at points E and F. Point H shows the location of another common rafter, however is has a shorter run and therefore a steeper slope. Up on top of the plan, the point G can be seen - here the common rafter meets the plan at an angle and is therefore a parallelogram-shaped section. There are 4 hip rafters. The square sectioned one will be in the right lower corner of the plan, to connect to corner D. Meeting corner A is a hip of an irregular section. At point B, the hip rafter is a triangular section and is rotated slightly. Finally, the hip rafter that meets the plan at corner C is a regular hexagon in section. If you look around the plan you will see the dark gray outlines of the four types of hip rafter, both to show their sections, and to show their footprints at slope.

In the next picture, the common rafters are erected:

Next, the parallelogram-shaped common rafter is placed:

Then the hip rafters:

Here we are looking at the triangular hip (closest) and hexagonal hip (left):

With the roof planes filled in, this is the sort of roof that would be produced:

So, I've run through that drawing 3 or 4 times now and have a good feel for it. Next I will try an application of the method by doing a similar drawing using a different plan and with other polygonal sections for the hips. Drilling the method by repetition is helpful when I don't have absolute understanding. When in doubt, draw it again!

Following the second version of the drawing, there is another 'theory' drawing to complete, termed "Théorie Des Niveaux De Devers". More on that in the next installment (<-- a link).

Thanks for coming by today.


  1. Impressively complex, certainly this early in the morning.

    I am not a scholar, but thinkering about a translation of "Théorie Des Devers De Pas", I found devers explained as inclination (as expected)
    DEVERS : manque d'aplomb. Inclinaison des faces d'une pièce de bois.

    'Pas' is more problematic as it is mostly used as a step, but in the case of 'retournant sur ses pas' the meaning is footprint. (the Robert says: trace laissée par un pied humain)

    Ok, that was the easy part, now the drawing.

  2. Hi Damien,

    You are 100% agree right with your point about the actual meaning of 'devers'. To translate "Théorie Des Devers De Pas" as "The theory of footprints of inclined pieces" seemed a little misleading, for, while the theory is definitely is about inclined pieces, it also deals with pieces which are plumb, and pieces of varying shapes (square, triangular, irregular, etc), and pieces which may be rotated on their lengthwise axis one way or another. The footprints can vary as a result of those various factors and how they combine and inter-relate. So, I took a bit of liberty with the term 'devers' and chose to use the word 'diverse' instead. The footprints may be of diverse shapes, depending upon the stick's slope, shape, and rotation. Hope that makes some sense - and I'm hardly a scholar of 19th century French, so my apologies to any French speakers if I have mangled your language here.

    I've added a sentence or two to the post in clarification of that, and good of you to make mention.

    That drawing is a bit complex, and yet it is one of the simplest in the entire book...ha-ha-ha, I may soon lose my mind! I've got triangles on my brain.



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