tag:blogger.com,1999:blog-6261993076995357307.post9062280566353010295..comments2023-11-05T06:16:56.961-05:00Comments on the Carpentry Way: Tréteau XXVIIIAnonymoushttp://www.blogger.com/profile/14328401081765407624noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-6261993076995357307.post-91393681417659334142010-02-23T05:27:55.811-05:002010-02-23T05:27:55.811-05:00Chris,
You are much more a specialist than I am. ...Chris,<br /><br />You are much more a specialist than I am. But I am also interested in the why. I agree that modern day carpentry lacks those complex diagonals, they look more like a torsion box with a large number of short transversal pieces. But apparently older Mansart roofs were different. I can imagine that a carpenter working on an early Mansart, say in 1540 on the Louvre, can have made repairs on a Gothic roof like that of Notre-Dame some years earlier, or the renovations of any second house in town. I expect the Notre-Dame roof to be a big alignment of A like structures crossed by a X. The X is in a different direction but heavily present. My impression is that a Mansart roof can be seen as a Gothic roof where the top part is removed, and the remaining lower structure stabilised by internal walls or added structures. For those carpenters Gothic or Mansart could have been business as usual, same skills, similar techniques. <br /><br />About jettying floors. We have (?had) taxes for extruding elements on a facade. A balcony is OK but you have to pay more taxes. A closed balcony? Even better, very impressive, I see you are a wealthy person. Etc. There is no way to avoid taxes. But as well as sagged roofs, I have seen many old sagged floors in masonry houses. Putting the weight of the wooden façade as counterweight on the extremities of a beam can help to reduce that problem. Of course you need to compensate the small foot-base with a stronger structure. We have the extra problem that beams had to be fixed on the front and back walls, and not to the common side walls. For narrow town houses this means that the beams are set to the greatest length.<br /><br />Apart from all that, I am quite happy and impressed to see your tréteau taking form.<br /><br />DamienAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-24472275276688980402010-02-22T22:08:40.014-05:002010-02-22T22:08:40.014-05:00Steve,
jeez, again! Thanks for noticing, and duly...Steve,<br /><br />jeez, again! Thanks for noticing, and duly corrected.<br /><br />And one more point in regards to Damien's comments, as I've had a little time to further reflect:<br /><br />The maison à colombages linked to in your post are not such a reasonable point of example for the issues I raised in regards to bracing, as such all-timber structures were already comparatively rare by the late 1800's in much of Europe. From what I gather the forest base was largely destroyed by the mid-1400's in many parts of Western Europe, due to both timber construction (buildings and ships) and, more particularly, the use of timber for fuel in the production of iron. In Mazerolle's book, along with two other period French carpentry books I have, there are no depictions of large buildings like those half-timbered ones in the Wikipedia link - virtually all the roofs to be seen described in the books are parked atop stone or brick walls. The only free-standing all-timber structures described, from this sample at least, are bridge centers, which are temporary structures, or small open air pavilions and the like. It seems by 1850 that the focus of timber carpentry in France, at least, was the roof only. So, the argument about the roof needing to hold together in the case of wall and foundation subsidence is less apt I would think when thick masonry walls are used.<br /><br />~ChrisAnonymoushttps://www.blogger.com/profile/14328401081765407624noreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-30729001228726760512010-02-22T20:29:56.762-05:002010-02-22T20:29:56.762-05:00Hi Chris,
Seems you've mislead us as well - w...Hi Chris,<br /><br />Seems you've mislead us as well - wasn't last entry #26? At least its not a big deal to fix and wouldn't matter much if never fixed (its not a tax form after all).<br />Anyway, enjoying the story.<br /><br />SteveAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-79832414908012854922010-02-22T19:21:48.300-05:002010-02-22T19:21:48.300-05:00Damien,
thanks so much for your comment. I am sur...Damien,<br /><br />thanks so much for your comment. I am sure that style/tradition, and its later blind imitation, plays a very large role in architecture the world over. My point however was not about the use of bracing and crosses in wall structures, which are obvious to view, but was directed in particular to the use of cross-bracing in splayed post structures, like a hipped roof.<br /><br />Your point about stabilizing roofs, in regards to these St. André's Crosses at least, doesn't entirely make sense to me, but is food for thought. Hipped and Mansard roofs are inherently stable shapes after all. Yes, if the foundation subsides or a wall buckles/deforms, then the roof will be subject to unusual loads which will likely lead to its ultimate deformation. There are buildings which have lasted for a long time and have a less-than ideal roof structural design - case in point being the numerous roofs in the area in which I now live that are of the common rafter type, with the ridgeline distinctly sagged in the middle and wall bulging outward pronouncedly at the mid-plate area. Not something worth imitating despite its durability. <br /><br />Given that braces work in compression, they will both help and harm the roof as these loads from wall/foundation problems are applied in various directions. However, the issue is not the roof in this scenario, but the foundation and/or walls, and to design the roof to compensate for wall or foundation insufficiencies seems a slightly odd way to go about things. Why not improve foundation and wall frame detailing?<br /><br />Gabled roofs are not so stable as hipped ones of course, and the addition of some form of bracing in the roof plane makes good sense in that case. <br /><br />I have no issue with wind bracing on plumb walls (in fact I like that idea a lot), providing it is detailed properly. <br /><br />Conversely, I wonder how many contemporary French timber structures employ St. A's crosses in the roofs they build? <br /><br />In regards to wall bracing it has been noted by other writers that wealth display on old half-timbered structures was accomplished, in one way, by adding lots of extra and decorative bracing to the outside walls. Many of the buildings linked to in your comment feature purely decorative bracing in many places.<br /><br />Your final point, about jettying one floor above the next, as far as I know had more to do with working around tax rates which were based upon ground floor building footprints, and for the purpose of providing some overhang to protect merchant wares or operations (and the lower wall framing, as you noted) at ground level, as the roofs in general in Western European framing have but modest overhangs. I don't think that an argument can be made for the jettying of floors adding especially to overall stability, as the structures become top-heavy if it is carried on too much. It's more logical and easier to do when buildings are located one against another in a row. The most *stable* arrangement for a detached structure, generally speaking, is to have a wide base and a smaller, lighter top structure, like a pyramid. Of course, a pyramid would not be a practical residential building form!<br /><br /><br /><br />~ChrisAnonymoushttps://www.blogger.com/profile/14328401081765407624noreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-31741632505862090172010-02-22T17:50:45.597-05:002010-02-22T17:50:45.597-05:00<>
I think that the use of crosses is also ...<><br /><br />I think that the use of crosses is also a matter of tradition. If one looks to wooden, sometimes medieval, houses (maison à colombages) one can see that in some styles crosses are massively used and other times not at all. I think it is an expression of local style. Some of these houses can be seriously out of plumb, most likely those without crosses. In an old house nothing is straight. Examples of styles can be seen on:<br />http://fr.wikipedia.org/wiki/Maison_à_colombages<br /><br />I think that stabilising roofs is important, as many old roofs have a stability problem. And certainly Mansard roofs where the beams do not rest on massive walls, and the volume of the structure is mainly kept to the roof surface itself.<br /><br />Another notable technique, seen on some examples of colombages, to set each floor more outward than the previous, is also about stability, this one to keep the horizontal beams and floors balanced and thus straight, as well as protect them from the weather.<br /><br />DamienAnonymousnoreply@blogger.com