Regular Hip Rafter with Jack Rafter par rembarrement

In this course I will show you how to find the cuts using the rembarrement method.

Purpose of the course



Reminders about the rembarrement method


The Jack Rafter Head Cuts


See what happens if you are not accurate enough


The Hip Rafter Head Cuts


The Jack Rafter Footprint on the Hip


If you have questions about this course and/or need more detailled pictures of the process, go to Forum-Charpente/ English Forum/ Beginners/ Regular Hip Rafter with Jack Rafter par rembarrement.

Download: RegHipWJackRembarrement.pdf

A few concepts...

..to know, about French Timber Framing, before starting.

Since a few weeks two English people join me to help on writing this blog.

We exchanged a lot and I conclude from our discussion that one of the biggest problems is that the  English language does not have translations for French timber framing terms. This is why I decided to keep some French words. But these French words need to be explained, that the purpose of this course.

-        “La sablière”: this word has two meanings, it is the wall-plate(*) - the piece of wood lying on the wall on which carry the rafters. In le trait it is also the theoretical line which represents the lowest plane of the roof. This line is in the same plane as the base line (ligne de trave). It is located at the intersection of the base line and the "lattis". This is the meaning in which we are going to use it.

-       " Le lattis": This word also has two meanings. It is a lath or tiling-batten but in le trait, it refers to the plane of the roof at the top of the rafters to which the tiling-battens are nailed. In French we say it is where the carpenter's work finishes and the tiler's or slater's work begins. When we draw the surface development of this plane - la herse of le lattis - we draw this surface in its true dimensions and angles.

-        “la herse”: a developed view of a plane in which lines in that plane are shown in their true lengths and at their true angles. La herse - or developed surface view - is obtained by 'rotating or folding' a surface into a (usually) horizontal plane about a line sometimes referred to as a hinge-line (for a roof surface the rotation line is “la sablière”).

-     “la vue par bout” or The end view: Is the auxiliary plane developed from perpendiculars to both the elevation and plan of the line formed by the meeting of two planes. It is used to show the end view of a component in that plane. The angle formed where these two planes meet is the dihedral angle. A hip rafter lies along the line formed by the meeting of the side and the end planes of a roof. When the auxiliary plane is developed by hinging it down into the plan view, the end view of the hip rafter is shown in its true dimensions and angles.

-        “le rabattement”: Is the technique we employ to rotate a figure about a line and by which that figure is moved from one plane to another. So to draw la herse of a roof, we have to do le rabattement of the real length of the profile rafter. In this case the line of rotation (the folding line), is la sablière. Another case in which “le rabattement” is used, is to show the underside of a piece of wood by rotating it a ¼ turn.

Note: study case drawn on Concepts_01.pdf file is delimited by the a-b-c-d letters on the drawing on the Concepts_02.pdf file.

Download: Concepts_01.pdf and Concepts_02.pdf

The basics of hip

There are two ways to design a hip in traditional French timber framing:

-        “L’arêtier sur lierne”

-        “L’arêtier sur tasseaux”

I didn’t find any translation for those words.

What they have in common: the sides are plumb, backing cuts (or not) and the principal hip rafter can be thicker than the hip rafter.

“L’arêtier sur lierne”

In French, “une lierne” is an element, often of small size, set against another element. 

In this case, the hip rafter is set above the principal hip rafter. 

The jack rafters are set against the hip rafter. 

The purlins are set against the principal rafter.

Following the chosen wood sections, there can have a claw to the purlin.

Depending on the chosen wood sections of the hip jack rafters and the purlins, the rafter can be designed with one single piece of wood.

Download: AreLierne_eng.pdf

“L’arêtier sur tasseaux”

In this case, the hip rafter and the principal hip rafter are separated: the purlins come between these two elements, unlike in the previous case. 

The hip jack rafters are set against the hip rafter (and can sometimes have a claw). 

The purlins are set on the principal hip rafter, they can’t have a claw but need to be cut at the top, to give a support to the hip rafter. 

The top face of the principal hip rafter need to be notched to let the passage of the purlins. 

A cleat has to be set on the principal hip rafter to avoid the rotation of the purlins. 

Sometimes the support is not wide enough for the hip rafter, in this case the best way is to do “un chevron d’arêtier chanlatté” (translation?). 

It’s a rotated hip rafter, composed in two pieces aligned with the top of the roof and supported by the purlins. 

In this case the hip jack rafters do not have plumb cuts but square cuts.

Download: AreTasseaux_eng.pdf

Elevations Comparison

This article is to explain the difference between a truss elevation and a profile rafter elevation.

The profile rafter is a theorical line (the French word is: "chevron d'emprunt", "emprunt" meaning: that has no existence.)

Do not confuse it with the Common Rafter. 

On the plan view a profile rafter is ALWAYS perpendicular to the overhang. 

Wisely used in “l’art du trait”, it is THE reference in French carpentry.

Bounded by three lines:

               - The run line (or base line), always horizontal, this line is located at the lowest top point of the roof. Its length corresponds to the width of the roof. (fr = ligne de trave).
Identified by this symbol:

                     - The axis line: (or rise line), always vertical, this line’s length correspond to the rise of the roof. (fr = ligne d’axe).
     Identified by this symbol:

                    - The battern: top of the roof. It’s the border line between the frame and the roofing.

      Unlike the profile rafter, a truss is not necessary perpendicular to the overhang (e.g. on a sloped ridge building). Its elevation is used to design it, that means that the dimensions of the pieces of wood composing it need to be know.
      On the opposite a profile rafter has no element. It has to be drawn only with simple lines (French : "par simple ligne".)

Download: ElevationsComparison.pdf

WHAT IS "LE REMBARREMENT"

"Le rembarrement" is one of the three methods used in french carpentry traditional scribing.

It has two meanings:

-        Drawing: this method requires to plot accurately the dimensions of the timbers to determine the intersecting points of the cuts. The next step requires to move those points from the plan view to the elevation view. 

-       -        Marking timbers: the carpenter puts the timber on the full-scale drawing (on the floor, called “l’épure” in French) and moves the points from the drawing to the timber, then turns it to finalize the marking.

      This method can be used only on straight and square timbers.

The general meaning of this word is: moving a point from one context to another.

WHERE DO I START ?

The training I offer is organized into three parts: beginners, intermediate and advanced.

The beginner section contains all the basic knowledge needed for further learning French scribing. The main objective of this section is to help students acquire the spatial vision and the discovery of the main methods used in "le trait" to be able to determine all the cuts necessary to perform a work of carpentry.

"La herse" (real surface), hip rafter, valley rafter, purlin rafter and jack rafter cuts.

The intermediate part of this study deepens the study of more complex structures.

The advanced part will reach to the most complex part of the French scribing: 

- “le dévers” (rotated timbers) 

- “le croche” (curved timbers).

During this training course you will learn about three techniques used in French carpentry scribing:

- "le rembarrement" (see here what this is)

- "la sauterelle" (see here what this is)

- "l'alignement", which is a mix of the two other methods. (only to advanced)

If you know absolutely nothing about the French Scribing process, be sure to start with the beginner section.

WHAT IS "LA SAUTERELLE" ?

"La sauterelle" is a tool (a bevel square). 

It's also one of the three processes used to find the cuts of the Timbers.

Based on the intersections plans of the faces of the components. 

The results are angles and length. 

This process does not need to put the timbers on the ground plan: we measure the length, set the bevel gauge at the cutting angles and mark them on the timbers.

The real name of this tool is “false square” in French, but we carpenters call it “sauterelle”, which means “grasshopper” according to the fact that this tool looks like the hind legs of the grasshopper. 

Many animals names are used in French carpentry terminology. 

The name of the process is “à la sauterelle”.

Unlike the "rembarrement" method, there is no need here to draw the dimensions of the timbers.

WHY THIS BLOG ?

My purpose with this blog is to help non-French speaking people to understand our French Timber Framing Traditional Scribing system.

This system called “le trait” or “l’art du trait” is inscribed on the Representative List of the Intangible Cultural Heritage of Humanity, by UNESCO, since 2009.

Scribing Tradition in French Timber Framing

 “..Scribing is a combination of the graphic processes used in France since the thirteenth century that make it possible to express accurately through the design the actual volumes of a building, its interlocking, and the characteristics of the wooden components…”

“..Through this process, the carpenter can determine all the components before they are built, however complex they are, and thus be sure that all the assemblies will fit together perfectly when the timber frame is built…”

The purpose of this blog is to teach you the art of scribing as it was relayed to me by my elders.