In any major city that features an historical center, the list of attractions advertised by tourist guides seldom includes what, in my opinion, would constitute the destination's most important part: historical residential buildings.

Unlike cathedrals and palaces, these are hardly ever carefully designed, nor elegantly engineered.

In Paris, these buildings are from two to five stories high, and, from the second floor and up, their facades are tilted backwards from the street. This, I believe, is a unique Paris feature: you won't find anything like it in any other city: neither in France, nor anywhere else.

Sometimes, the facade of the ground floor is titled the other way, so that the building looks like a section of a pyramid placed on top of a section of an upended pyramid.

What's the idea?

I have heard a number of theories about this phenomenon, none of them backed by data from a reliable source.

The examples in the photos illustrate my point. Please note that the sketch of the Place de Greve, where the tilt is also clearly visible, dates back to 1750, which proves that the tilt is by no means a recent phenomenon.

So, what's the big idea? From the engineering point of view, what would be the advantage of tilting the facade backwards? Does it have anything to do with the building materials (limestone, I believe, rather than bricks and lime render)? Any ideas?enter image description here

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    $\begingroup$ There are the architectural concerns - space and lighting requirements for tall buildings in a congested city setting with pre-existing narrow roads/ally ways. $\endgroup$
    – r13
    May 13 '21 at 19:04
  • $\begingroup$ @r13: Perhaps. But why would this only occur in Paris, and not in any other French, German, or Italian city? $\endgroup$
    – Ricky
    May 13 '21 at 20:25
  • $\begingroup$ If you are visiting Frence, why not ask the architect or the local building officials. $\endgroup$
    – r13
    May 13 '21 at 21:45
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    $\begingroup$ You pisted this the other day - edit and improve, don’t just repost. $\endgroup$
    – Solar Mike
    May 14 '21 at 0:50
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    $\begingroup$ @Ricky OK. The question piqued my interest because of the potential effects on convective heat transfer: with that slope, each side of the wall has a Rayleigh-B\'enard cell superimposed on the Schmidt-Beckmann boundary layer convection that would be the whole story at a vertical wall - and the R-B cell on the outside has infinite Rayleigh number. $\endgroup$ May 18 '21 at 19:52

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