Wednesday, September 28, 2011

Lucarne Et Nolet Sur Arêtier

Finally into some new territory with the Mazerolle book. Up next was a dormer parked on a hip corner, or 'sur arêtier'. There was only half as much text to plow through, however this drawing also had its peculiarities and challenges to overcome  - and mislabeled portions of the drawing. I'm ready for this sort of thing now and don't let a few hiccups (or 'hiccoughs', as you may prefer) slow me down. As with the other dormer problems in the book, this one revolves around determining the shape of the noulet, which are irregularly-shaped pieces of wood that are employed instead of valley rafters. In a future post I'll take a look at this French traditional solution in comparison to other methods of dealing with dormer valleys.

Here's the drawing in the text, plan view at the bottom right, elevation views at the top:

Click on any drawing to see a larger version.

The illustration of the plan shows the noulet and their relationship to the rest of the dormer and the main roof:

The upper surface of the noulet conforms to the upper surface of the dormer roof, while the lower surface of the noulet has to conform to the top of the main roof's hip rafter, which is at a different slope than the dormer roof.

Here's a close up of the plan drawing of the noulet - notice that on their left side they are shown abutting the side of the diagonal strut which helps carry the load - note point 'L' as the intersection point:

Point H' in the above drawing appears to be the end of the hip rafter resting upon the central support beam in the dormer, however all the hinge lines in this drawing are actually at the top of the molding, which sits a bit above the wall plate. Thus, what appears to be the end of the hip rafter in the above drawing is actually, in my drawing, 3 cm above the true end point of the hip. That raised hinge line adds to the drawing difficulty.

So, I followed faithfully along with the drawing and what it indicated should be done, until I had completed the plan and the 3D development of the noulet. I then placed the noulet into the roof. Tah-dah! However there was a problem - notice the lower end of the noulet at the top of the wall plate:

Another view:

You can see that there is a hole there are the lower meeting point of the noulet, the dormer wall plate, and the side of the strut. That won't fly. That's not sound constructional practice.

Here's a look at the top end of the noulet, where you can see the triangular section which results when it must conform to both the hip rafter and the ridgeline of the dormer:

I realized that a better solution - perhaps the intended solution (?) if I assume a mis-drawing in the text, is that the triangular shape of the noulet can only join cleanly here if the lower end of the noulet can rest partially on the bevel on the hip support strut, and partially on the plate. So, I redrew, which involved raising the elevation of the plate and the dormer rafters in reference to everything else, and a whole lot of cascading little issues arose as a result. When I had straightened everything out again, I produced a new noulet section and slid it back into the dormer roof. Here's the result:

Another view:

This is a much cleaner and more workman-like solution I feel. No gaps, and the noulet conforms to the required intersecting planes, the dormer roof, the wall plate, and the hipped main roof. That's my solution and I'm sticking to it until someone can show me some way that the text's proposed version can work cleanly. In the above drawing I have sized the bevel on the strut to coincide exactly with the inner top corner of the noulet, however the bevel could be made larger with no effect upon anything else in the structure.

By the time I was done, I had built myself a virtual dormer on a hip:

A look at the plan view, with the noulet in yellow:

I then placed that dormer into another drawing where I am aggregating all the dormer models, along with who knows what else I might dredge out of Mazerolle:

A closer view, showing, among other things, the raised molding along the dormer wall plates:

From the inside looking toward the dormer - this shows the hip strut bracing more clearly:

Side elevation view:

And in context with the other dormers I have completed so far:

A plan view of all the dormers:

That's 4 dormers down and just one more to go now. The last one shown is a dormer which is situated higher than the ridge of the main roof. It also is a noulet problem though I'm sure I'll learn a few other things as well. Mazerolle hides the secrets in these drawing,s and I keep uncovering more of them as I move along.  Despite the problems in the book with the illustrations, and details omitted in the text portions, it is a brilliant work, and there is much to learn if one puts the time and effort in.

Thanks for coming by the blog today. Comments always welcome.

Friday, September 23, 2011

Do you play the Guitare?

Nope, that wasn't a typo in the title- guitare, more often spelled guitarde, is a French word meaning 'alcove', and is a special carpentry term you won't find readily in a French dictionary. Trust me, I've looked at a few.  If you do an image search for guitare you will find images of, guess what?: guitars. Even when looking for guitarde, lots of Fenders, etc., show up in the search results. Well, you might come across one or two guitardes which are not strung or played.

Most of the classic French 18th/19th century carpentry drawing books show an example or three of guitardes - they often associate to prow roofs on dormers, typically are found over the main entrance to a building, and are sometimes seen under balconies as well. I've got a few photos to share, just to give you an idea. You gotta hand it to the French traditional carpentry tradition - fascinating!

This first set of photos are by Compagnon Jonathon Lahaye.

The modern versions are often built with laminated material, with the older examples cut and joined from solid stock:

These next pictures associate to the Compannage Museum. A maquette with an imperiale roof over the guitarde:

Multiple guitardes form an intriguing vaulting:

The above example looks like a development from a structure featured in Delataille's 19th century layout books:

Ah one:


And three - not really a guitarde, but neat all the same:

 They put them all together and installed them above the entry:

 The circular prow roofed dormer is a frequent candidate for the guitarde underpinnings:

Some places, like this one from a Chateau on Rue De La Gare (Station Street, Paris), get a little more, um, carried away:

This one is a little worse for wear and could use a rebuild:

Now I may be biased, but this is pretty damn neat:

A commune called La Veurdure in Alliers, France has some splendid examples on this building, photographed by Jean Beaubreuil:

If we saw more dormers like this, the world would surely be a better place, no?:


Not sure which way to turn?:

Another intriguing double dormer with intertwined guitardes, all atop a circular balcon with guitarde:

There is an example in Mazerolle's book of a circular wall with circular balcony and guitarde. How crazy is that?

Chalon-sur-Saône is another commune having a guitarde dormer - I wonder what the connection (or attraction, perhaps?) with these structures and communes might be?:

Above photograph also by Jean Beaubreuil. This one too, same location:

Hope you enjoyed the tour. I look forward to working on the geometrical drawings for these sorts of structures one day.

Speaking of geometrical drawing, my friend Tim Moore has started a new blog (<- link) on stereotomy - I hope you'll check it out. I'm following it already and look forward to see where he goes. 

Thanks for coming by the Carpentry Way today. Hope you liked the pics, and if you visit France, take a look up from the sidewalk once in a while to see if you spot any more interesting constructions. These guitarde dormers are often 5 stories up. I'm always looking for more pictures!

Tuesday, September 20, 2011

Following Mazerolle: Lucarne Et Nolet Éventail (III)

I've been on a bit of a French Carpentry drawing tear for the past couple of weeks. With the lucarne biaise (see the previous post) out of the way, I moved on to the next dormer in the line-up, the fan-tailed dormer, or lucarne éventail.

When I last tackled (<-- a link) this drawing, I got hung up on a part of the 2D drawing concerning the ridgepole and the alignment of it's undersurface to the body of the roof:

"With a little reverse drawing from the completed 3D parts on top of the 2D plan, I was able to determine the correct arrangement. I still don't get everything on the drawing, but had enough to produce developed views of all the parts in the end."

While I solved it using 3D, the impression I had formed is that the drawing in the book was defective, and that was where my study left off last year. Again, I had some useful recent correspondence with Tim Moore in France, and he pointed out that the picture of the ridge pole cross section on the 2D plan had to be showing an oblique section of the ridge. That made perfect sense. If one cuts a housing on a beam for a hip rafter, for example, the lower surface of the hip rafter, while square to the hip itself, forms a sloped line on the face of the beam which receives it. Once I got that - and it seems obvious in hindsight - I realized that I could probably work the remaining drawing bugs out after all.

Here is the (mostly) completed 2D plan drawing of the fantail dormer:

I left off developing the lines for the rotated hip rafters and associated jack rafters, as those are fairly straightforward. It does end up with a lot of lines on the page all the same.

The éventail dormer completed (right), and placed into the model with it's neighbours, the nolet biaise (middle) and nolet carré (left):

A view of the same, looking the other direction:

As you can see in this plan view, the fantail dormer takes its name from the spreading rafter plates:

To further add complication, the ridgepole descends on the dormer roof:

So, I am caught back up to where I left off last year and am now wanting to forge ahead with some more Mazerolle study. There are two more dormers to deal with in the text, and that is what I will focus on. Next up: Lucarne Et Nolet Sur Arêtier (dormer on a hip corner). I hope you'll stay tuned to the Carpentry Way.

Monday, September 19, 2011

Following Mazerolle: Lucarne Biaise À Fronton. Nolet Biais (III)

I think - just perhaps - I've got the layout for the dormer on a bias sorted now, though with some small variations from the text's example. The text shows the valley pieces, noulet, being joined at their peak with a form of birds mouth joint. I reconfigured it so that the pieces would join with a miter, which means that one of the valley pieces cannot come from a square section stick of wood. The valley pieces are shaped as trapezoids in cross section, so that they can simultaneously lie flat on the main roof and, on their other sides allow a common rafter to join to them with a simple (that is, non-compound) miter cut. And of course their top and bottom edges are in plane with the dormer roof surface, both atop the rafters and in plane with the under-surfaces of the rafters.

This is the completed dormer:

On the front is the tympanum molding.

Same view, with roofing boards and main roof plane removed:

The boards which lay down on the roof surface and travel on a bias, serving to receive the dormer wall plate on each side, are parallelograms in section.

Here's a view normal to the front, which is aligned to the edge of the roof:

A snapshot of the 2D drawing fun which produced the complicated parts of the dormer framing - the noulet in particular:

In some cases I needed to reverse engineer from the 3D to determine exactly what was going on in spots. It did all come together in the end.

I then stuck the biased dormer on a drawing with the hip roofed, otherwise orthogonal version:

Another view:

Plan view of the completed biased dormer:

Last, a view from the other side:

That's two dormers down finally, and the drawing method is starting to make more sense. Maybe I'm kidding myself though.  A long way to go yet in this study. Each drawing in the book of a given set of examples, like dormers, is a little more complicated than the previous example. Next up is the lucarne éventail, a fan-shaped dormer with a descending ridge and rotated rather than backed hip rafters. It is definitely the most attractive dormer example in the book to my eyes. I had a go at it about a year ago and ran into some difficulties with the 2D part, though I was able to complete it in 3D. Recent conversations with Tim Moore in France though have allowed me to see some new things in that drawing and I feel like I should be able to surmount the previous problems. I'm sure in collaboration we can get it done.

Thanks for coming by the Carpentry Way today.