Monday, September 20, 2021



It is an easy mistake to make. We look at native architecture or other responses to environmental challenges and mistakenly think that the solutions that evolved over the millennia are "quaint" and not driven by functionality.

If you approached an aeronautical engineer and asked them to estimate the "lift" of a wing profile that resembled a classic, Japanese temple and they would laugh you out of the room. It has negative lift. That is, the wind pushes DOWN on the structure.

Concave roofs are not easy to build. There are reasons why they evolved other than the fact that they would be photogenic some thousand years in the future.

Since the timber-frame construction is light-weight but strong in compression, it is able to resist typhoon winds when topped with the classic concave-sharp ridge-concave profile while modern, flatter roofs are lifted and ripped off buildings in high winds.

Fluid flowing over the top of a convex surface creates lift. Great pains are taken to prevent the fluid from "separating" from the surface and creating back-eddies.

Fluid flowing over the top of a concave surface creates negative lift. The sharp feature at the ridge of the Japanese temple is guaranteed to create separation.

Japanese engineering is not a new phenomena.


  1. Also, many of the 'original' roofs were built with bamboo and tiles, which causes more disruption due to the 'uneven' surfaces.

  2. The Japanese, and the Chinese also, invented some of the most complex joinery for wood timbers. One of the more simple ones, is the Keyed Scarf Joint, used to make a long timber out of two shorter ones. Some of their furniture joinery is mind boggling.


    Yes Nova, I think, had a couple of shows on it. Looks like some clips under the link. A show on a bridge rebuild with wood joints and another on forbibben city columns on a shake table. Good stuff.

  4. I have always admired the ancient or even antique ways things were made. The unknown Roman concrete that still works is one. My dad and grandad taught me the old ways of cutting rafters so they support the weight of the roof, no notching like we do now on the top plate. Of course balloon framing was normal then too. But there is so much to be learned from and adapted by just realizing that our ancestors weren't stupid. They figured it out without computers by hard won victories and bitter failures. They weren't dim by any stretch.

    Probably, their intellectual prowess was greater due to their ability to focus for long periods reading BOOKS, learning in class rooms, and having to work from their youth on. Learning from the old journeymen was no easy task. They didn't put up with anything they deemed less than total concentration. I apprenticed under one of those... And extremely glad I had that opportunity.... well, I do NOW....

  5. The secret of roman concrete has been solved. Seawater.


Readers who are willing to comment make this a better blog. Civil dialog is a valuable thing.